refactor: split single-file main.c into modular .h/.c pairs

Decompose the 778-line src/main.c into 7 focused modules with separate
headers for code isolation and parallel agent development:

  types.h          shared types: PlayerState, SilenceRegion, UILayout, constants
  player.{h,c}     audio playback: load, play, pause, seek, update, format_time
  study.{h,c}      study mode: silence detection, portion navigation, auto-pause
  ui.{h,c}         rendering + input: fonts, colors, drawing, keyboard/mouse
  config.{h,c}    UI layout persistence (moved UILayout to types.h)
  layout_editor.{h,c}  layout editor tab (unchanged)
  main.c           thin composition root (main loop, tabs, platform glue)

Module boundaries follow the dispatch-project style:
- .h files are contracts (self-contained, #pragma once, forward-declare)
- .c files are private (static helpers, no cross-module .c includes)
- All shared state passed by pointer (PlayerState*/UIState*)
- font_data.h (xxd-generated array definition) included in exactly one .c

Updated documentation (AGENTS.md, ORCHESTRATOR.md, GLOSSARY.md, README.md,
tasks.md) and bin/ scripts (dispatch-style conventions, added bin/build-web).

Build: make clean && make -j$(nproc) exits 0 with zero warnings.

20 files changed, 1345 insertions, 873 deletions

diff --git a/.dispatch/build-agent.md b/.dispatch/build-agent.md
index cbf21dd..1a6ed43 100644
--- a/.dispatch/build-agent.md
+++ b/.dispatch/build-agent.md
@@ -31,11 +31,20 @@ You MUST NOT write to `src/*` or any other source files.
 - Font header generation: `build/font_data.h` is a prerequisite built by
   running `xxd -i` on the font file in `resources/`. If no font file exists,
   the build should still work (font_data.h just won't define `FONT_EMBEDDED`).
+  **`font_data.h` is an array definition, not a declaration** — it must be
+  included in exactly ONE `.c` file (currently `ui.c`). Multiple includes cause
+  multiple-definition link errors.
 - The `bin/build-web` script builds for Web/WASM via `emcc` + `emar`. Keep it
   functional.
 - All SRCS should be `$(wildcard src/*.c)` so new modules auto-compile.
 - Use `-j$(nproc)` in any make invocation inside scripts for parallelism.
 
+## bin/ script conventions
+- Every script starts with `#!/usr/bin/env bash` and `set -euo pipefail`.
+- Every script derives `SCRIPT_DIR` and `PROJECT_DIR` and `cd "$PROJECT_DIR"`.
+- Every script forwards extra args via `"$@"`.
+- One script per operation — the filename describes what it does.
+
 ## Verification
 1. `make clean && make -j$(nproc)` — exits 0, zero warnings from project code
 2. `make windows -j$(nproc)` — exits 0, zero warnings from project code
diff --git a/.gitignore b/.gitignore
index 02bd1f1..b584502 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,21 @@
+# Build artifacts
 build/
+build-web/
+
+# External dependencies (cloned separately)
 deps/
+
+# Runtime assets (fonts — embedded at build time)
 resources/
+
+# Runtime config
+study-player.cfg
+
+# Agent harness scratch (orchestrator→agent prompts, agent→orchestrator reports)
+prompts/
+reports/
+
+# OS / editor
+.DS_Store
+*.swp
+*~
diff --git a/AGENTS.md b/AGENTS.md
index 9e9c600..99a2054 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -15,8 +15,11 @@
   APIs (windowing, audio, input, font loading, drawing). Never include glfw,
   miniaudio, or stb headers directly. For web: `emscripten.h` is allowed behind
   `#ifdef PLATFORM_WEB`.
-- **`build/font_data.h`** (generated by `xxd` from `resources/`) is included
-  behind `#include "font_data.h"` guard its use with `#if FONT_EMBEDDED`.
+- **`build/font_data.h`** (generated by `xxd` from `resources/`) is an
+  **array definition**, not a declaration. Include it in EXACTLY ONE `.c` file
+  (currently `ui.c`). Guard its use with `#if FONT_EMBEDDED`. Never include it
+  from a `.h` file or from multiple `.c` files — that causes multiple-definition
+  link errors.
 - **No dynamic allocation** unless paired with an explicit free in the same
   module's cleanup. No leaks.
 - **No VLAs** (variable-length arrays on the stack). Use fixed-size buffers or
@@ -59,9 +62,9 @@
 
 - **Build is the primary test.** If `make` exits 0 with zero warnings, your
   module compiles and links correctly.
-- **If you add a new `.c` file**, note it in your report — the orchestrator
-  updates the Makefile's `SRCS` list (this is orchestrator-owned build wiring,
-  NOT your responsibility).
+- **If you add a new `.c` file**, note it in your report. The Makefile uses
+  `$(wildcard src/*.c)` so new modules are auto-discovered — no `SRCS` edit
+  needed. The orchestrator owns the Makefile for any structural changes.
 
 ## 6. What you may read from other modules
 
diff --git a/GLOSSARY.md b/GLOSSARY.md
index 4d05b8b..b78b66c 100644
--- a/GLOSSARY.md
+++ b/GLOSSARY.md
@@ -7,25 +7,30 @@
 
 | Term | Definition | Avoid calling it... |
 |------|-----------|-------------------|
-| **PlayerState** | The single struct holding all mutable runtime state: loaded audio, playback status, silence regions, study mode flag | "app state", "context", "global state" |
+| **PlayerState** | The single struct holding all mutable runtime state: loaded audio, playback status, silence regions, study mode flag. Defined in `types.h`. | "app state", "context", "global state" |
+| **UIState** | The struct holding UI-only state: fonts, colors, and interaction flags (smartPlayHeld). Defined in `ui.h`. | "ui context", "render state" |
+| **UILayout** | Pixel positions for every on-screen element, persisted to `study-player.cfg`. Defined in `types.h`, loaded/saved by the config module. | "layout config", "positions" |
 | **speaking portion** | A contiguous segment of audio between two silence regions (i.e. the "meaningful content"). 0-based index. | "section", "segment", "clip", "part" |
 | **silence region** | A detected gap in audio where amplitude stays below threshold for ≥ minDuration. Normalized 0–1. | "pause", "gap", "quiet zone" |
 | **study mode** | Boolean toggle (`PlayerState.studyMode`). When ON, auto-pauses at silence boundaries. | "auto-pause mode", "learning mode" |
 | **seek** | Jump playback position to a specific time (seconds). `player_seek(PlayerState*, float)`. | "scrub", "jump", "skip" |
-| **auto-pause** | The study-mode mechanism that pauses playback when entering a silence region. | "auto-stop", "silence break" |
+| **auto-pause** | The study-mode mechanism that pauses playback when entering a silence region. Implemented by `study_auto_pause_check`. | "auto-stop", "silence break" |
 | **padding zone** | The 0.25s "breathing room" added around speaking portions (silence shrunk by 0.25s on each side) to avoid auto-pausing during natural speech pauses. | "grace period", "buffer zone" |
 | **portion navigation** | Jumping between speaking portions via keys (V/B) or section buttons. | "chapter skip", "section nav" |
-| **embedded font** | A `.otf`/`.ttf` font file converted to `build/font_data.h` via `xxd`, compiled into the binary. Guarded by `#if FONT_EMBEDDED`. | "baked font", "built-in font" |
+| **smart play** | A hold-to-override button that resumes playback and suppresses auto-pause while held. State tracked in `UIState.smartPlayHeld`. | "hold play", "override button" |
+| **embedded font** | A `.otf`/`.ttf` font file converted to `build/font_data.h` via `xxd`, compiled into the binary. Guarded by `#if FONT_EMBEDDED`. Included in exactly one `.c` file (`ui.c`). | "baked font", "built-in font" |
 
 ## Module names
 
 | Module | Files | Owns |
 |--------|-------|------|
-| **types** | `src/types.h` | `PlayerState`, `SilenceRegion`, all enums, defines, constants |
-| **player** | `src/player.h`, `src/player.c` | Audio loading, playback control, seek, time formatting |
-| **study** | `src/study.h`, `src/study.c` | Silence detection, study mode logic, portion navigation |
-| **ui** | `src/ui.h`, `src/ui.c` | All rendering, font/color initialization, input handling |
-| **main** | `src/main.c` | Entry point, main loop, platform glue |
+| **types** | `src/types.h` | `PlayerState`, `SilenceRegion`, `UILayout`, all constants (`SCREEN_W`, `SCREEN_H`, `MAX_*`). Pure header — no `.c`. |
+| **player** | `src/player.h`, `src/player.c` | Audio loading, playback control, seek, music-stream update, time formatting |
+| **study** | `src/study.h`, `src/study.c` | Silence detection, speaking-portion navigation, auto-pause logic |
+| **ui** | `src/ui.h`, `src/ui.c` | Font/color initialization, all rendering, all input handling (player tab), `UIState` |
+| **config** | `src/config.h`, `src/config.c` | `UILayout` persistence (load/save to `study-player.cfg`) |
+| **layout_editor** | `src/layout_editor.h`, `src/layout_editor.c` | Layout editor tab (drag-to-reposition UI elements), raygui implementation |
+| **main** | `src/main.c` | Entry point, main loop, tab switching, drag-drop/web file loading, platform glue |
 
 ## Build terms
 
diff --git a/ORCHESTRATOR.md b/ORCHESTRATOR.md
index b5d5319..4a41f68 100644
--- a/ORCHESTRATOR.md
+++ b/ORCHESTRATOR.md
@@ -37,15 +37,18 @@ the `.h` contract is underspecified — that is a bug, not normal.
    declarations over pulling in heavy headers.
 2. **No cross-module `.c` includes** — ever. If module A needs module B, A
    includes `B.h`, never `B.c`.
-3. **All shared mutable state goes through `PlayerState*`** — no global
-   variables. File-scope statics are only for module-private state (e.g. fonts
-   in the UI module).
+3. **All shared mutable state goes through `PlayerState*`** (or `UIState*` for
+   UI-only state) — no global variables. File-scope statics are only for
+   module-private state (e.g. fonts in the ui module).
 4. **One `.o` per module** — each `.c` compiles independently. The linker
    resolves dependencies. This is what makes parallel-agent waves possible.
 5. **Zero warnings on `-Wall -Wextra`** — the build is the trust signal. If
    `make` barks, the wave is not green.
 6. **Raylib is the only external dependency** — no pulling in new libraries
    without a design decision.
+7. **`font_data.h` is a definition, not a declaration** — include it in exactly
+   ONE `.c` file (currently `ui.c`). Including it from multiple translation
+   units causes multiple-definition link errors.
 
 ---
 
@@ -236,13 +239,19 @@ authoritative.
   single file owns it. Summon a **temporary multi-knowledge agent** with
   read/write to the 2–3 relevant files (it MAY see `.c` files — exception to
   the visibility rule), as their temporary exclusive owner.
+- **Multiple-definition link error on `embedded_font_data`:** `font_data.h` is
+  an `xxd`-generated array definition, not a declaration. It must be included
+  in exactly ONE `.c` file (currently `ui.c`). If a new module needs the font
+  data, either route it through `ui.h` functions or move the include to a
+  single owner and expose `extern` declarations.
 - **CR (change-request) in a report:** if it's **build/config** (`Makefile`,
   `.gitignore`, `deps/` reference) the orchestrator edits it directly, then
   re-verifies with `make`. If it's **implementation** (a `.c` file), the
   orchestrator **summons the owning agent** — it does NOT edit `.c` files
   itself.
 - **Makefile changes:** the Makefile is orchestrator-owned (it's build wiring,
-  §6). If a module addition requires updating `SRCS`, the orchestrator does it.
+  §6). It uses `$(wildcard src/*.c)` so new modules auto-compile. Structural
+  changes (new targets, new platforms) are orchestrator-owned.
 
 ---
 
@@ -296,9 +305,9 @@ authoritative.
   windows` cross-compiles for Windows via MinGW. Both platforms must work.
   Use `#ifdef PLATFORM_LINUX` / `_GLFW_X11` vs `_GLFW_WIN32` guards where
   platform differences exist.
-- **No global mutable state.** All shared state passes through `PlayerState*`.
-  File-scope statics are for module-private data only (e.g. cached fonts in the
-  UI module).
+- **No global mutable state.** All shared state passes through `PlayerState*`
+  (or `UIState*` for UI-only state). File-scope statics are for module-private
+  data only.
 - **C99 only.** No C11/C17 features the compiler doesn't support. No C++
   in `.c` files.
 - **Raylib is the only external library.** No SDL, no GLFW standalone, no
@@ -315,7 +324,7 @@ authoritative.
   ORCHESTRATOR.md  the orchestrator's operating manual (this file)
   GLOSSARY.md      canonical vocabulary + aliases-to-avoid
   tasks.md         live progress checklist / milestone log
-  Makefile         build — orchestrator-owned, never touched by agents
+  Makefile         build — orchestrator-owned, never touched by module agents
   README.md        project overview, build instructions, usage guide
 
   .dispatch/
@@ -326,14 +335,6 @@ authoritative.
       zero-warnings.md
       contracts-are-h.md
 
-  .rules/                   original design plans (reference only)
-    plan/
-      plan.md
-      phase1.md
-      phase2.md
-      phase3.md
-    ideas/
-
   notes/
     restructure-plan.md     the full module split design + rationale + wave plan
 
@@ -341,21 +342,25 @@ authoritative.
   reports/   (gitignored — agent→orchestrator reports)
 
   src/
-    types.h          CONTRACT — shared types, enums, constants (PlayerState, etc.)
-    player.h         CONTRACT — audio playback: load, seek, play, pause, format_time
+    types.h          CONTRACT — shared types, enums, constants (PlayerState, SilenceRegion, UILayout)
+    player.h         CONTRACT — audio playback: load, seek, play, pause, update, format_time
     player.c         IMPL
-    study.h          CONTRACT — study mode: detect_silence, portion navigation
+    study.h          CONTRACT — study mode: detect_silence, portion navigation, auto-pause
     study.c          IMPL
-    ui.h             CONTRACT — rendering: init, render_frame, destroy
-    ui.c             IMPL
-    main.c           COMPOSITION ROOT — entry point + main loop
+    ui.h             CONTRACT — rendering + input: init, destroy, handle_input, render_player, render_empty
+    ui.c             IMPL (owns font_data.h include)
+    config.h         CONTRACT — UILayout persistence: config_load, config_save
+    config.c         IMPL
+    layout_editor.h  CONTRACT — layout editor tab: init, draw
+    layout_editor.c  IMPL (owns raygui implementation)
+    main.c           COMPOSITION ROOT — entry point + main loop + platform glue
 
   deps/
     raylib/          raylib library (built as static lib)
-    raygui/          raygui library (reserved, not yet used)
+    raygui/          raygui library (single-header, implemented in layout_editor.c)
 
   bin/
-    build            build script for desktop (Windows cross-compile)
+    build            build script for desktop (Linux native / Windows cross-compile)
     build-web        build script for WASM/web
     clean            clean build artifacts
     serve            serve web build locally
@@ -370,9 +375,9 @@ authoritative.
 
 ## 8. Current status & how to run
 
-See `tasks.md` for the live checklist. The project is a working single-file
-`src/main.c` (778 lines) that needs to be split into modules as described in
-`notes/restructure-plan.md`.
+See `tasks.md` for the live checklist. The module split is **complete** — the
+single-file `src/main.c` (778 lines) has been decomposed into 7 modules:
+`types.h`, `player`, `study`, `ui`, `config`, `layout_editor`, `main`.
 
 **Desktop build:**
 ```bash
@@ -398,6 +403,5 @@ make clean && make -j$(nproc)
 bin/clean    # removes build/ and build-web/
 ```
 
-When the module restructure is complete, `make` builds for the host platform.
-`make windows` cross-compiles for Windows via MinGW. The font header generation
-is a make prerequisite.
+The font header generation is a make prerequisite — `build/font_data.h` is
+generated by `xxd -i` from the first `.otf`/`.ttf` in `resources/`.
diff --git a/README.md b/README.md
index d701b93..e4d0043 100644
--- a/README.md
+++ b/README.md
@@ -4,6 +4,25 @@ A keyboard-driven MP3 player built with [raylib](https://github.com/raysan5/rayl
 
 <img width="1923" height="1125" alt="image" src="https://github.com/user-attachments/assets/a2e2363e-cc0a-4936-8b04-0f32886ff9d8" />
 
+## Architecture
+
+The project is built from composable modules, each a `.h` contract + `.c`
+implementation pair. This separation enables parallel agent development —
+modules communicate only through header-file contracts.
+
+```
+src/types.h          shared types: PlayerState, SilenceRegion, UILayout, constants
+src/player.{h,c}     audio playback: load, play, pause, seek, update, format_time
+src/study.{h,c}      study mode: silence detection, portion navigation, auto-pause
+src/ui.{h,c}        rendering + input: fonts, colors, drawing, keyboard/mouse
+src/config.{h,c}    UI layout persistence (study-player.cfg)
+src/layout_editor.{h,c}  layout editor tab (drag-to-reposition)
+src/main.c           composition root: main loop, tab switching, platform glue
+```
+
+See `GLOSSARY.md` for the canonical vocabulary and `ORCHESTRATOR.md` for the
+multi-agent development workflow.
+
 ### Dependencies
 
 Clone the following repositories into the `deps/` directory:
@@ -35,14 +54,27 @@ If no font file is present, the app falls back to the built-in raylib default fo
 ### Building
 
 ```bash
-bin/build
+# Linux native
+make -j$(nproc)
+
+# Windows cross-compile
+make windows -j$(nproc)
 ```
 
-The output binary is `build/study-player.exe`.
+The output binary is `build/study-player` (Linux) or `build/study-player.exe` (Windows).
+
+Alternatively, use the convenience scripts:
+
+```bash
+bin/build      # desktop build (Linux native + Windows cross-compile)
+bin/clean      # remove build artifacts
+bin/build-web  # WASM/web build via emscripten
+bin/serve      # serve web build on port 8080
+```
 
 ### Usage
 
-Run the `.exe` on Windows (or under Wine). Drag an `.mp3` file onto the window to load it.
+Run the binary on Linux (or the `.exe` on Windows / under Wine). Drag an `.mp3` file onto the window to load it.
 
 | Key | Action |
 |---|---|
@@ -89,10 +121,13 @@ When Study Mode is **off**, C pauses and N resumes without any section-seeking b
 ### Project Structure
 
 ```
-src/main.c        Application source
-deps/raylib/      raylib (cloned separately)
-deps/raygui/      raygui (cloned separately)
-build/            Build output (gitignored)
-resources/        Font files (gitignored)
-bin/              Build and utility scripts
+src/               modular C source (one .h/.c pair per module)
+deps/raylib/       raylib (cloned separately)
+deps/raygui/       raygui (cloned separately)
+build/             Build output (gitignored)
+resources/         Font files (gitignored)
+bin/               Build and utility scripts
+AGENTS.md          Subagent constitution (C99 rules, module boundaries)
+ORCHESTRATOR.md    Multi-agent orchestration workflow
+GLOSSARY.md        Canonical vocabulary
 ```
diff --git a/bin/build b/bin/build
index e3f5200..d27d6f6 100755
--- a/bin/build
+++ b/bin/build
@@ -1,32 +1,21 @@
 #!/usr/bin/env bash
+# bin/build — desktop build (Linux native + Windows cross-compile)
+#
+# Usage:
+#   bin/build           # Linux native build
+#   bin/build windows   # Windows cross-compile
+#   bin/build clean     # clean + build
+#
+# Any args after the target are forwarded to make.
+
 set -euo pipefail
 
-SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
-cd "$SCRIPT_DIR"
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PROJECT_DIR="$(dirname "$SCRIPT_DIR")"
 
-# Generate embedded font header from first font file in resources/
-mkdir -p build
-FONT_HEADER="build/font_data.h"
-FONT_FILE="$(find resources/ -maxdepth 1 -type f \( -iname '*.otf' -o -iname '*.ttf' \) 2>/dev/null | head -n1 || true)"
+cd "$PROJECT_DIR"
 
-if [ -n "$FONT_FILE" ]; then
-    if [ ! -f "$FONT_HEADER" ] || [ "$FONT_FILE" -nt "$FONT_HEADER" ]; then
-        echo "Embedding font: $FONT_FILE"
-        xxd -i "$FONT_FILE" > "$FONT_HEADER.tmp"
-        # Normalize variable names to embedded_font_data / embedded_font_data_len
-        VARNAME=$(grep -oP 'unsigned char \K[a-zA-Z0-9_]+' "$FONT_HEADER.tmp" | head -1)
-        sed -i "s/${VARNAME}/embedded_font_data/g" "$FONT_HEADER.tmp"
-        echo '#define FONT_EMBEDDED 1' >> "$FONT_HEADER.tmp"
-        mv "$FONT_HEADER.tmp" "$FONT_HEADER"
-    fi
-else
-    echo "No font file found in resources/, using default raylib font"
-    cat > "$FONT_HEADER" <<'EOF'
-/* No font embedded */
-static unsigned char embedded_font_data[] = {0};
-static unsigned int embedded_font_data_len = 0;
-#define FONT_EMBEDDED 0
-EOF
-fi
+TARGET="${1:-all}"
+shift || true
 
-make -j$(nproc) "$@"
+make "$TARGET" -j"$(nproc)" "$@"
diff --git a/bin/build-web b/bin/build-web
new file mode 100755
index 0000000..453ee92
--- /dev/null
+++ b/bin/build-web
@@ -0,0 +1,85 @@
+#!/usr/bin/env bash
+# bin/build-web — WASM/web build via Emscripten
+#
+# Produces build-web/index.{html,js,wasm} from src/ + web/shell.html.
+# Requires emcc + emar (Emscripten SDK) on PATH.
+#
+# Usage:
+#   bin/build-web
+
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PROJECT_DIR="$(dirname "$SCRIPT_DIR")"
+
+cd "$PROJECT_DIR"
+
+SRC_DIR="src"
+BUILD_DIR="build-web"
+RAYLIB_SRC="deps/raylib/src"
+RAYLIB_LIB="$BUILD_DIR/libraylib.a"
+
+COMMON_INCS="-I$BUILD_DIR -I$RAYLIB_SRC -I$RAYLIB_SRC/external/glfw/include -Ideps/raygui/src"
+DEFINES="-DPLATFORM_WEB -DGRAPHICS_API_OPENGL_ES2"
+CFLAGS="-std=c99 -O2 $COMMON_INCS $DEFINES"
+
+mkdir -p "$BUILD_DIR"
+
+# --- Font header (same logic as Makefile) ---
+FONT_HEADER="$BUILD_DIR/font_data.h"
+FONT_FILE="$(find resources -maxdepth 1 -type f \( -iname '*.otf' -o -iname '*.ttf' \) -print -quit 2>/dev/null || true)"
+
+if [ -n "$FONT_FILE" ] && command -v xxd >/dev/null 2>&1; then
+    echo "  XXD    $(basename "$FONT_FILE") -> $FONT_HEADER"
+    xxd -i "$FONT_FILE" > "$FONT_HEADER.tmp"
+    VARNAME="$(grep -oP 'unsigned char \K[a-zA-Z0-9_]+' "$FONT_HEADER.tmp" | head -1)"
+    sed -i "s/${VARNAME}/embedded_font_data/g" "$FONT_HEADER.tmp"
+    echo '#define FONT_EMBEDDED 1' >> "$FONT_HEADER.tmp"
+    mv "$FONT_HEADER.tmp" "$FONT_HEADER"
+else
+    echo "  INFO   No font file or xxd unavailable — using default font"
+    printf '/* No font embedded */\nstatic unsigned char embedded_font_data[] = {0};\nstatic unsigned int embedded_font_data_len = 0;\n#define FONT_EMBEDDED 0\n' > "$FONT_HEADER"
+fi
+
+# --- Build raylib for web ---
+RAYLIB_SRCS="$RAYLIB_SRC/rcore.c $RAYLIB_SRC/rshapes.c $RAYLIB_SRC/rtextures.c $RAYLIB_SRC/rtext.c $RAYLIB_SRC/rmodels.c $RAYLIB_SRC/raudio.c"
+RAYLIB_OBJS=""
+for src in $RAYLIB_SRCS; do
+    obj="$BUILD_DIR/raylib_$(basename "${src%.c}").o"
+    echo "  CC     $src"
+    emcc $CFLAGS -w -c -o "$obj" "$src"
+    RAYLIB_OBJS="$RAYLIB_OBJS $obj"
+done
+
+echo "  AR     $RAYLIB_LIB"
+emar rcs "$RAYLIB_LIB" $RAYLIB_OBJS
+
+# --- Build application ---
+APP_SRCS="$(find "$SRC_DIR" -name '*.c')"
+APP_OBJS=""
+for src in $APP_SRCS; do
+    obj="$BUILD_DIR/$(basename "${src%.c}").o"
+    echo "  CC     $src"
+    emcc $CFLAGS -Wall -Wextra -c -o "$obj" "$src"
+    APP_OBJS="$APP_OBJS $obj"
+done
+
+# --- Link ---
+SHELL_HTML="web/shell.html"
+if [ ! -f "$SHELL_HTML" ]; then
+    echo "Error: $SHELL_HTML not found" >&2
+    exit 1
+fi
+
+echo "  LINK   $BUILD_DIR/index.html"
+emcc $CFLAGS -o "$BUILD_DIR/index.html" $APP_OBJS "$RAYLIB_LIB" \
+    -s USE_GLFW=3 \
+    -s WASM=1 \
+    -s ASYNCIFY \
+    -s SHELL_FILE="$PWD/$SHELL_HTML" \
+    -s EXPORTED_FUNCTIONS='["_main","_load_file_web"]' \
+    -s EXPORTED_RUNTIME_METHODS='["ccall","cwrap"]' \
+    --preload-file resources \
+    "$@"
+
+echo "Build complete: $BUILD_DIR/index.html"
diff --git a/bin/clean b/bin/clean
index 91ee73b..202ee9d 100755
--- a/bin/clean
+++ b/bin/clean
@@ -1,7 +1,15 @@
 #!/usr/bin/env bash
+# bin/clean — remove all build artifacts
+#
+# Usage:
+#   bin/clean
+
 set -euo pipefail
 
-SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
-cd "$SCRIPT_DIR"
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PROJECT_DIR="$(dirname "$SCRIPT_DIR")"
+
+cd "$PROJECT_DIR"
 
-make clean
+rm -rf build build-web
+echo "Cleaned build/ and build-web/"
diff --git a/bin/serve b/bin/serve
index 931e2db..cb6fb06 100755
--- a/bin/serve
+++ b/bin/serve
@@ -1,13 +1,21 @@
 #!/usr/bin/env bash
+# bin/serve — serve the web build locally
+#
+# Usage:
+#   bin/serve          # serve on port 8080
+#   bin/serve 9000     # serve on port 9000
+
 set -euo pipefail
 
-SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
-cd "$SCRIPT_DIR"
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PROJECT_DIR="$(dirname "$SCRIPT_DIR")"
+
+cd "$PROJECT_DIR"
 
 BUILD_DIR="build-web"
 
 if [ ! -f "$BUILD_DIR/index.html" ]; then
-    echo "Error: Web build not found. Run 'bin/build-web' first."
+    echo "Error: Web build not found. Run 'bin/build-web' first." >&2
     exit 1
 fi
 
diff --git a/src/config.h b/src/config.h
index 57824b5..42ccca2 100644
--- a/src/config.h
+++ b/src/config.h
@@ -1,24 +1,15 @@
 #pragma once
 
-typedef struct {
-    float titleY;
-    float titleX;
-    float barY;
-    float barHeight;
-    float barWidth;
-    float barX;
-    float statusY;
-    float statusX;
-    float btnRadius;
-    float helpY;
-    float helpX;
-    float btnY;
-    float btnCenterX;
-    float smartPlayY;
-    float smartPlayX;
-    float secNavY;
-    float secNavX;
-} UILayout;
+/* config.h — UI layout persistence contract.
+ *
+ * Owns: loading/saving UILayout to study-player.cfg.
+ * UILayout itself lives in types.h (the shared-types header). */
 
+#include "types.h"
+
+/* Load layout from <exeDir>/study-player.cfg; returns 1 if loaded, 0 if
+ * the file was missing or unreadable (defaults are applied either way). */
 int config_load(const char *exePath, UILayout *layout);
+
+/* Save layout to <exeDir>/study-player.cfg; returns 1 on success. */
 int config_save(const char *exePath, const UILayout *layout);
diff --git a/src/main.c b/src/main.c
index 49d1ab2..91dc984 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1,12 +1,23 @@
+/* main.c — composition root.
+ *
+ * Owns: window/audio init, main loop, tab switching + config save,
+ * drag-drop / web file loading, platform glue.
+ * Delegates to: player, study, ui, config, layout_editor. */
+
 #define _POSIX_C_SOURCE 200809L
+
 #include "raylib.h"
-#include <string.h>
-#include <ctype.h>
+#include "raygui.h"
+
 #include <stdio.h>
+#include <string.h>
+
+#include "types.h"
 #include "config.h"
 #include "layout_editor.h"
-#include "raygui.h"
-#include "font_data.h"
+#include "player.h"
+#include "study.h"
+#include "ui.h"
 
 #ifdef PLATFORM_LINUX
 #include <unistd.h>
@@ -15,321 +26,27 @@
 #include <emscripten/emscripten.h>
 #endif
 
-#define SCREEN_W 1920
-#define SCREEN_H 1080
-
-#define MAX_SILENCE_REGIONS 4096
+/* ------------------------------------------------------------------ */
+/* Shared state (needed for emscripten main loop callback)            */
+/* ------------------------------------------------------------------ */
 
-typedef struct {
-    float start;  /* normalized 0..1 */
-    float end;    /* normalized 0..1 */
-} SilenceRegion;
-
-typedef struct {
-    Music music;
-    bool loaded;
-    bool playing;
-    float duration;
-    float currentTime;
-    char filename[256];
-    SilenceRegion silence[MAX_SILENCE_REGIONS];
-    int silenceCount;
-    bool studyMode;
-    bool wasInSilence;    /* for detecting silence entry */
-    int  lastSilenceIdx;  /* index of silence region we were last in, or -1 */
-    int skipAutoUpdate;   /* frames to skip auto-updating currentTime */
-    double lastVPress;    /* unused, kept for struct compat */
-} PlayerState;
-
-/* --- File-scope state (needed for emscripten main loop callback) --- */
 static PlayerState state = { 0 };
+static UIState     ui;
+static UILayout    layout;
+static char        exeDir[512];
+static int         activeTab = 0;
+static int         prevTab   = 0;
 
-static Font fontSmall, font, fontMed, fontLarge, fontHelp;
-static float szSmall, szHelp, szFont, szMed, szLarge;
-
-static Color bgColor;
-static Color textColor;
-static Color accentColor;
-static Color mutedColor;
-static Color barBgColor;
-static Color btnHoverColor;
-
-static UILayout layout;
-
-static int activeTab = 0;
-static int prevTab = 0;
-static bool smartPlayHeld = false;
-static char exeDir[512];
-
-static int strcasecmp_ext(const char *a, const char *b)
-{
-    while (*a && *b) {
-        if (tolower((unsigned char)*a) != tolower((unsigned char)*b)) return 1;
-        a++; b++;
-    }
-    return *a != *b;
-}
-
-static void detect_silence(const char *path, PlayerState *s, float threshold, float minDuration)
-{
-    s->silenceCount = 0;
-    Wave wave = LoadWave(path);
-    if (wave.data == NULL || wave.frameCount == 0) return;
-
-    /* Convert to 32-bit float mono for easy analysis */
-    WaveFormat(&wave, wave.sampleRate, 32, 1);
-    float *samples = (float *)wave.data;
-    unsigned int totalFrames = wave.frameCount;
-    float sampleRate = (float)wave.sampleRate;
-
-    /* Scan in chunks of ~10ms */
-    int chunkSize = (int)(sampleRate * 0.01f);
-    if (chunkSize < 1) chunkSize = 1;
-    float minFrames = minDuration * sampleRate;
-
-    bool inSilence = false;
-    unsigned int silenceStart = 0;
-
-    for (unsigned int i = 0; i < totalFrames; i += chunkSize)
-    {
-        unsigned int end = i + chunkSize;
-        if (end > totalFrames) end = totalFrames;
-
-        /* Find peak amplitude in this chunk */
-        float peak = 0.0f;
-        for (unsigned int j = i; j < end; j++)
-        {
-            float v = samples[j];
-            if (v < 0) v = -v;
-            if (v > peak) peak = v;
-        }
-
-        if (peak < threshold)
-        {
-            if (!inSilence) { silenceStart = i; inSilence = true; }
-        }
-        else
-        {
-            if (inSilence)
-            {
-                unsigned int len = i - silenceStart;
-                if ((float)len >= minFrames && s->silenceCount < MAX_SILENCE_REGIONS)
-                {
-                    s->silence[s->silenceCount].start = (float)silenceStart / (float)totalFrames;
-                    s->silence[s->silenceCount].end   = (float)i / (float)totalFrames;
-                    s->silenceCount++;
-                }
-                inSilence = false;
-            }
-        }
-    }
-    /* Close any trailing silence */
-    if (inSilence)
-    {
-        unsigned int len = totalFrames - silenceStart;
-        if ((float)len >= minFrames && s->silenceCount < MAX_SILENCE_REGIONS)
-        {
-            s->silence[s->silenceCount].start = (float)silenceStart / (float)totalFrames;
-            s->silence[s->silenceCount].end   = (float)totalFrames / (float)totalFrames;
-            s->silenceCount++;
-        }
-    }
-
-    UnloadWave(wave);
-
-    /* Pad speaking portions by shrinking silence regions 0.25s on each side */
-    if (s->duration > 0.0f)
-    {
-        float padNorm = 0.25f / s->duration; /* 0.25s in normalized units */
-        for (int i = 0; i < s->silenceCount; i++)
-        {
-            s->silence[i].start += padNorm;
-            s->silence[i].end   -= padNorm;
-            if (s->silence[i].start >= s->silence[i].end)
-            {
-                /* Region too small after padding, remove it */
-                for (int j = i; j < s->silenceCount - 1; j++)
-                    s->silence[j] = s->silence[j + 1];
-                s->silenceCount--;
-                i--;
-            }
-        }
-    }
-}
-
-static const char *basename_from_path(const char *path)
-{
-    const char *last = path;
-    for (const char *p = path; *p; p++) {
-        if (*p == '/' || *p == '\\') last = p + 1;
-    }
-    return last;
-}
-
-static void seek_to(PlayerState *s, float target)
-{
-    if (target < 0.0f) target = 0.0f;
-    if (target > s->duration) target = s->duration;
-    SeekMusicStream(s->music, target);
-    s->currentTime = target;
-    s->skipAutoUpdate = 3; /* skip a few frames to let audio engine catch up */
-}
+/* ------------------------------------------------------------------ */
+/* File loading (drag-drop desktop / JS callback web)                  */
+/* ------------------------------------------------------------------ */
 
-static void format_time(float seconds, char *buf, int bufsize)
-{
-    int total = (int)seconds;
-    if (total < 0) total = 0;
-    int h = total / 3600;
-    int m = (total % 3600) / 60;
-    int s = total % 60;
-    if (h > 0)
-        snprintf(buf, bufsize, "%d:%02d:%02d", h, m, s);
-    else
-        snprintf(buf, bufsize, "%d:%02d", m, s);
-}
-
-/* Find the silence region index containing the normalized position, or -1 */
-static int find_silence_at(PlayerState *s, float pos)
-{
-    for (int i = 0; i < s->silenceCount; i++)
-        if (pos >= s->silence[i].start && pos < s->silence[i].end) return i;
-    return -1;
-}
-
-/* Get the start of speaking portion N (0-based). Returns normalized position. */
-static float speaking_portion_start(PlayerState *s, int portion)
-{
-    if (portion <= 0) return 0.0f;
-    if (portion > s->silenceCount) return s->silence[s->silenceCount - 1].end;
-    return s->silence[portion - 1].end;
-}
-
-/* Get which speaking portion (0-based) the normalized position is in.
-   During silence, returns the previous speaking portion. */
-static int current_speaking_portion(PlayerState *s, float pos)
-{
-    int portion = 0;
-    for (int i = 0; i < s->silenceCount; i++)
-    {
-        if (pos >= s->silence[i].end)
-            portion = i + 1;
-        else
-            break;
-    }
-    return portion;
-}
-
-/* Total number of speaking portions */
-static int total_speaking_portions(PlayerState *s)
-{
-    return s->silenceCount + 1;
-}
-
-/* Get the seek target (in seconds) for jumping to a speaking portion.
-   Lands 2 render-frames (~33ms) into the padding zone. */
-static float segment_seek_target(PlayerState *s, int portion)
-{
-    float pos = speaking_portion_start(s, portion);
-    float target = pos * s->duration + (2.0f / 60.0f);
-    if (target < 0.0f) target = 0.0f;
-    if (target > s->duration) target = s->duration;
-    return target;
-}
-
-/* Check if normalized position is in the padding zone of a speaking portion.
-   The padding zone is [speaking_start, speaking_start + 0.25s/duration]. */
-static bool in_padding_zone(PlayerState *s, float pos, int portion)
-{
-    if (s->duration <= 0.0f) return false;
-    float padNorm = 0.25f / s->duration;
-    float start = speaking_portion_start(s, portion);
-    return (pos >= start && pos < start + padNorm);
-}
-
-static void draw_text_centered(Font f, const char *text, float centerX, float y, float fontSize, Color color)
-{
-    float spacing = fontSize * 0.03f;
-    Vector2 size = MeasureTextEx(f, text, fontSize, spacing);
-    float x = centerX - size.x / 2.0f;
-    DrawTextEx(f, text, (Vector2){ x, y }, fontSize, spacing, color);
-}
-
-/* Draw a right-pointing triangle (play icon) centered at cx,cy */
-static void draw_play_icon(float cx, float cy, float size, Color color)
-{
-    float half = size / 2.0f;
-    Vector2 v1 = { cx - half * 0.7f, cy - half };
-    Vector2 v2 = { cx - half * 0.7f, cy + half };
-    Vector2 v3 = { cx + half * 0.8f, cy };
-    DrawTriangle(v1, v2, v3, color);
-}
-
-/* Draw two vertical bars (pause icon) centered at cx,cy */
-static void draw_pause_icon(float cx, float cy, float size, Color color)
-{
-    float half = size / 2.0f;
-    float barW = size * 0.25f;
-    float gap = size * 0.15f;
-    DrawRectangleRec((Rectangle){ cx - gap - barW, cy - half, barW, size }, color);
-    DrawRectangleRec((Rectangle){ cx + gap, cy - half, barW, size }, color);
-}
-
-/* Draw a left-pointing triangle (seek back) centered at cx,cy */
-static void draw_seek_back_icon(float cx, float cy, float size, Color color)
-{
-    float half = size / 2.0f;
-    Vector2 v1 = { cx + half * 0.7f, cy - half };
-    Vector2 v2 = { cx - half * 0.8f, cy };
-    Vector2 v3 = { cx + half * 0.7f, cy + half };
-    DrawTriangle(v1, v2, v3, color);
-}
-
-/* Draw a right-pointing triangle (seek forward) centered at cx,cy */
-static void draw_seek_fwd_icon(float cx, float cy, float size, Color color)
-{
-    float half = size / 2.0f;
-    Vector2 v1 = { cx - half * 0.7f, cy - half };
-    Vector2 v2 = { cx - half * 0.7f, cy + half };
-    Vector2 v3 = { cx + half * 0.8f, cy };
-    DrawTriangle(v1, v2, v3, color);
-}
-
-static bool button_hit(float cx, float cy, float radius)
-{
-    if (!IsMouseButtonPressed(MOUSE_BUTTON_LEFT)) return false;
-    Vector2 m = GetMousePosition();
-    float dx = m.x - cx;
-    float dy = m.y - cy;
-    return (dx * dx + dy * dy) <= (radius * radius);
-}
-
-/* Load an audio file into the player (used by both desktop drag-drop and web file input) */
 static void load_audio_file(const char *path)
 {
-    const char *ext = GetFileExtension(path);
-    if (ext == NULL || strcasecmp_ext(ext, ".mp3") != 0) return;
-
-    if (state.loaded)
-    {
-        StopMusicStream(state.music);
-        UnloadMusicStream(state.music);
-        state.loaded = false;
-        state.playing = false;
-    }
-
-    state.music = LoadMusicStream(path);
-    state.duration = GetMusicTimeLength(state.music);
-    state.loaded = true;
-    state.playing = true;
-
-    const char *base = basename_from_path(path);
-    strncpy(state.filename, base, sizeof(state.filename) - 1);
-    state.filename[sizeof(state.filename) - 1] = '\0';
-
-    PlayMusicStream(state.music);
+    if (!player_load(&state, path)) return;
 
     /* Detect silence regions (threshold: 0.015, min duration: 0.75s) */
-    detect_silence(path, &state, 0.015f, 0.75f);
+    study_detect_silence(path, &state, 0.015f, 0.75f);
 
     char titleBuf[320];
     snprintf(titleBuf, sizeof(titleBuf), "Study Player - %s", state.filename);
@@ -345,10 +62,13 @@ void load_file_web(const char *path)
 }
 #endif
 
-/* --- Main loop body (one frame) --- */
+/* ------------------------------------------------------------------ */
+/* Main loop body (one frame)                                         */
+/* ------------------------------------------------------------------ */
+
 static void update_frame(void)
 {
-    /* --- 1.1 Drag & drop file loading (desktop only) --- */
+    /* --- Drag & drop file loading (desktop only) --- */
 #ifndef PLATFORM_WEB
     if (IsFileDropped())
     {
@@ -359,394 +79,35 @@ static void update_frame(void)
     }
 #endif
 
+    /* --- Input (player tab only) --- */
     if (activeTab == 0)
-    {
-    /* --- Button clicks --- */
-    if (state.loaded)
-    {
-        /* Play/pause button */
-        if (button_hit(layout.btnCenterX, layout.btnY, layout.btnRadius))
-        {
-            if (state.playing)
-            {
-                PauseMusicStream(state.music);
-                state.playing = false;
-            }
-            else
-            {
-                ResumeMusicStream(state.music);
-                state.playing = true;
-            }
-        }
-
-        /* Section nav buttons */
-        {
-            float progress = (state.duration > 0.0f) ? state.currentTime / state.duration : 0.0f;
-            int portion = current_speaking_portion(&state, progress) + 1;
-            int total = total_speaking_portions(&state);
-            if (portion > total) portion = total;
-            float secBtnRadius = 35.0f;
-            float secPrevX = layout.secNavX - 65.0f;
-            float secNextX = layout.secNavX + 65.0f;
-            float secBtnY = layout.secNavY;
-
-            if (button_hit(secPrevX, secBtnY, secBtnRadius))
-            {
-                float pos = state.currentTime / state.duration;
-                int p = current_speaking_portion(&state, pos);
-                bool inSil = (find_silence_at(&state, pos) >= 0);
-                bool inPad = in_padding_zone(&state, pos, p);
-                if ((inSil || inPad) && p > 0) p--;
-                float target = segment_seek_target(&state, p);
-                seek_to(&state, target);
-                state.wasInSilence = false;
-                state.lastSilenceIdx = -1;
-            }
-            if (button_hit(secNextX, secBtnY, secBtnRadius))
-            {
-                float pos = state.currentTime / state.duration;
-                int p = current_speaking_portion(&state, pos);
-                if (p < total - 1) p++;
-                float target = segment_seek_target(&state, p);
-                seek_to(&state, target);
-                state.wasInSilence = false;
-                state.lastSilenceIdx = -1;
-            }
-        }
-
-        /* --- Smart play hold button input --- */
-        {
-            Rectangle smartBtn = { layout.smartPlayX, layout.smartPlayY, 200.0f, 80.0f };
-            Vector2 mouse = GetMousePosition();
-            bool overBtn = (mouse.x >= smartBtn.x && mouse.x <= smartBtn.x + smartBtn.width &&
-                            mouse.y >= smartBtn.y && mouse.y <= smartBtn.y + smartBtn.height);
-
-            if (IsMouseButtonPressed(MOUSE_BUTTON_LEFT) && overBtn) {
-                smartPlayHeld = true;
-                if (!state.playing) {
-                    ResumeMusicStream(state.music);
-                    state.playing = true;
-                }
-            }
+        ui_handle_input(&ui, &state, &layout);
 
-            if (IsMouseButtonDown(MOUSE_BUTTON_LEFT) && smartPlayHeld) {
-                /* Allow finger drift - stay held */
-            }
-
-            if (IsMouseButtonReleased(MOUSE_BUTTON_LEFT)) {
-                smartPlayHeld = false;
-            }
-
-            if (GetTouchPointCount() > 0 && smartPlayHeld) {
-                /* Touch fallback: keep held while touch points active */
-            }
-        }
-    }
-
-    /* --- Keyboard input --- */
-    if (state.loaded && IsKeyPressed(KEY_C) && state.playing)
-    {
-        PauseMusicStream(state.music);
-        state.playing = false;
-    }
-
-    if (state.loaded && IsKeyPressed(KEY_N) && !state.playing)
-    {
-        float pos = state.currentTime / state.duration;
-        int portion = current_speaking_portion(&state, pos);
-        float target = segment_seek_target(&state, portion);
-        seek_to(&state, target);
-        ResumeMusicStream(state.music);
-        state.playing = true;
-    }
-
-    if (state.loaded && IsKeyPressed(KEY_SPACE) && !state.playing)
-    {
-        ResumeMusicStream(state.music);
-        state.playing = true;
-    }
-
-    if (state.loaded && IsKeyPressed(KEY_V))
-    {
-        float pos = state.currentTime / state.duration;
-        int portion = current_speaking_portion(&state, pos);
-        bool inSil = (find_silence_at(&state, pos) >= 0);
-        bool inPad = in_padding_zone(&state, pos, portion);
-        if ((inSil || inPad) && portion > 0)
-            portion--;
-        float target = segment_seek_target(&state, portion);
-        seek_to(&state, target);
-        state.wasInSilence = false;
-        state.lastSilenceIdx = -1;
-    }
-
-    if (state.loaded && IsKeyPressed(KEY_B))
-    {
-        float pos = state.currentTime / state.duration;
-        int portion = current_speaking_portion(&state, pos);
-        int total = total_speaking_portions(&state);
-        if (portion < total - 1) portion++;
-        float target = segment_seek_target(&state, portion);
-        seek_to(&state, target);
-        state.wasInSilence = false;
-        state.lastSilenceIdx = -1;
-    }
-
-    /* Click-to-seek on progress bar */
-    if (state.loaded && IsMouseButtonPressed(MOUSE_BUTTON_LEFT))
-    {
-        Vector2 mouse = GetMousePosition();
-        if (mouse.x >= layout.barX && mouse.x <= layout.barX + layout.barWidth &&
-            mouse.y >= layout.barY && mouse.y <= layout.barY + layout.barHeight)
-        {
-            float target = ((mouse.x - layout.barX) / layout.barWidth) * state.duration;
-            seek_to(&state, target);
-        }
-    }
-
-    /* Arrow key seeking */
-    if (state.loaded && IsKeyPressed(KEY_LEFT))
-        seek_to(&state, state.currentTime - 5.0f);
-    if (state.loaded && IsKeyPressed(KEY_RIGHT))
-        seek_to(&state, state.currentTime + 5.0f);
-    if (state.loaded && IsKeyPressed(KEY_UP) && !state.playing)
-    {
-        ResumeMusicStream(state.music);
-        state.playing = true;
-    }
-    if (state.loaded && IsKeyPressed(KEY_DOWN) && state.playing)
-    {
-        PauseMusicStream(state.music);
-        float rewind = state.currentTime - 1.0f;
-        if (rewind < 0.0f) rewind = 0.0f;
-        SeekMusicStream(state.music, rewind);
-        state.currentTime = rewind;
-        state.playing = false;
-    }
-    /* Number key seeking (0-9 = 0%-90%) */
+    /* --- Music stream update + study auto-pause --- */
     if (state.loaded)
     {
-        for (int k = 0; k <= 9; k++)
-        {
-            if (IsKeyPressed(KEY_ZERO + k))
-            {
-                float target = state.duration * (k / 10.0f);
-                seek_to(&state, target);
-                break;
-            }
-        }
-    }
-    }
-
-    /* --- Music stream update --- */
-    if (state.loaded)
-    {
-        UpdateMusicStream(state.music);
-        if (state.playing)
-        {
-            if (state.skipAutoUpdate > 0)
-            {
-                state.skipAutoUpdate--;
-            }
-            else
-            {
-                state.currentTime = GetMusicTimePlayed(state.music);
-            }
-
-            /* Study mode: auto-pause at silence boundaries */
-            if (state.studyMode && state.duration > 0.0f)
-            {
-                float pos = state.currentTime / state.duration;
-                int silIdx = find_silence_at(&state, pos);
-                bool nowInSilence = (silIdx >= 0);
-
-                if (nowInSilence && !state.wasInSilence && !IsKeyDown(KEY_SPACE) && !smartPlayHeld)
-                {
-                    float target = segment_seek_target(&state, silIdx + 1);
-                    PauseMusicStream(state.music);
-                    SeekMusicStream(state.music, target);
-                    state.currentTime = target;
-                    state.playing = false;
-                    state.skipAutoUpdate = 3;
-                }
-                else if (!nowInSilence && state.wasInSilence && !IsKeyDown(KEY_SPACE) && !smartPlayHeld)
-                {
-                    int portion = current_speaking_portion(&state, pos);
-                    float target = segment_seek_target(&state, portion);
-                    PauseMusicStream(state.music);
-                    SeekMusicStream(state.music, target);
-                    state.currentTime = target;
-                    state.playing = false;
-                    state.skipAutoUpdate = 3;
-                }
-
-                state.wasInSilence = nowInSilence;
-                if (nowInSilence) state.lastSilenceIdx = silIdx;
-            }
-        }
+        player_update(&state);
+        if (state.studyMode && state.playing)
+            study_auto_pause_check(&state, ui.smartPlayHeld, IsKeyDown(KEY_SPACE));
     }
 
     /* --- Save layout on tab switch --- */
-    if (prevTab == 1 && activeTab == 0) {
+    if (prevTab == 1 && activeTab == 0)
         config_save(exeDir, &layout);
-    }
     prevTab = activeTab;
 
     /* --- Drawing --- */
     BeginDrawing();
-    ClearBackground(bgColor);
+    ClearBackground(ui.bgColor);
 
     char *tabNames[] = { "Player", "Layout" };
     GuiTabBar((Rectangle){ 0, 10, SCREEN_W, 32 }, tabNames, 2, &activeTab);
 
     if (activeTab == 0) {
-    if (state.loaded)
-    {
-        draw_text_centered(font, state.filename, layout.titleX, layout.titleY, szFont, mutedColor);
-
-        /* Progress bar */
-        float currentTime = state.currentTime;
-        float progress = (state.duration > 0.0f) ? currentTime / state.duration : 0.0f;
-        if (progress > 1.0f) progress = 1.0f;
-
-        Rectangle barBg = { layout.barX, layout.barY, layout.barWidth, layout.barHeight };
-        Rectangle barFill = { layout.barX, layout.barY, layout.barWidth * progress, layout.barHeight };
-        DrawRectangleRounded(barBg, 0.4f, 8, barBgColor);
-        if (progress > 0.001f)
-            DrawRectangleRounded(barFill, 0.4f, 8, accentColor);
-
-        /* Time labels */
-        char timeBuf[16];
-        int elapsedSec = (int)currentTime;
-        if (elapsedSec < 0) elapsedSec = 0;
-        int totalSec = (int)state.duration;
-        int remainSec = totalSec - elapsedSec;
-        if (remainSec < 0) remainSec = 0;
-
-        format_time((float)elapsedSec, timeBuf, sizeof(timeBuf));
-        float timeFontSize = szSmall;
-        float timeSpacing = timeFontSize * 0.03f;
-        Vector2 leftSize = MeasureTextEx(fontSmall, timeBuf, timeFontSize, timeSpacing);
-        DrawTextEx(fontSmall, timeBuf, (Vector2){ layout.barX - leftSize.x - 20, layout.barY + (layout.barHeight - timeFontSize) / 2.0f }, timeFontSize, timeSpacing, textColor);
-
-        char remainBuf[16];
-        format_time((float)remainSec, remainBuf, sizeof(remainBuf));
-        float rightX = layout.barX + layout.barWidth + 20;
-        DrawTextEx(fontSmall, remainBuf, (Vector2){ rightX, layout.barY + (layout.barHeight - timeFontSize) / 2.0f }, timeFontSize, timeSpacing, textColor);
-
-        /* Percent centered above progress bar */
-        char pctBuf[16];
-        int pct = (int)(progress * 100.0f);
-        snprintf(pctBuf, sizeof(pctBuf), "%d%%", pct);
-        bool inSilence = (find_silence_at(&state, progress) >= 0);
-        draw_text_centered(fontSmall, pctBuf, layout.barX + layout.barWidth / 2.0f, layout.barY - timeFontSize - 10, timeFontSize, textColor);
-
-        /* Playback status */
-        Color statusColor = (state.playing && inSilence) ? (Color){ 160, 40, 55, 255 } : accentColor;
-        draw_text_centered(font, state.playing ? "PLAYING" : "PAUSED", layout.statusX, layout.statusY, szFont, statusColor);
-
-        /* Buttons */
-        Vector2 mousePos = GetMousePosition();
-
-        /* Play/pause button */
-        Color playBtnColor = (state.playing && inSilence) ? (Color){ 160, 40, 55, 255 } : accentColor;
-        float ppx = layout.btnCenterX;
-        float pdx = mousePos.x - ppx, pdy = mousePos.y - layout.btnY;
-        bool hoverPP = (pdx*pdx + pdy*pdy) <= ((layout.btnRadius+5)*(layout.btnRadius+5));
-        DrawCircle((int)ppx, (int)layout.btnY, layout.btnRadius + 8, playBtnColor);
-        if (hoverPP) DrawCircle((int)ppx, (int)layout.btnY, layout.btnRadius + 8, btnHoverColor);
-        if (state.playing)
-            draw_pause_icon(ppx, layout.btnY, 50, textColor);
+        if (state.loaded)
+            ui_render_player(&ui, &state, &layout);
         else
-            draw_play_icon(ppx, layout.btnY, 50, textColor);
-
-        /* Speaking portion counter with prev/next section buttons */
-        {
-            int portion = current_speaking_portion(&state, progress) + 1;
-            int total = total_speaking_portions(&state);
-            if (portion > total) portion = total;
-            char portionBuf[32];
-            snprintf(portionBuf, sizeof(portionBuf), "%d/%d", portion, total);
-            float secBtnRadius = 35.0f;
-            float portionY = layout.secNavY - szSmall - secBtnRadius - 10.0f;
-            float portionSpacing = szSmall * 0.03f;
-            Vector2 portionSize = MeasureTextEx(fontSmall, portionBuf, szSmall, portionSpacing);
-            float portionX = layout.secNavX - portionSize.x / 2.0f;
-            DrawTextEx(fontSmall, portionBuf, (Vector2){ portionX, portionY }, szSmall, portionSpacing, mutedColor);
-
-            /* Section nav buttons */
-            float secPrevX = layout.secNavX - 65.0f;
-            float secNextX = layout.secNavX + 65.0f;
-            float secBtnY_draw = layout.secNavY;
-
-            float sd3 = mousePos.x - secPrevX, sd4 = mousePos.y - secBtnY_draw;
-            bool hoverSecPrev = (sd3*sd3 + sd4*sd4) <= (secBtnRadius*secBtnRadius);
-            DrawCircle((int)secPrevX, (int)secBtnY_draw, secBtnRadius, (Color){ 50, 50, 70, 255 });
-            if (hoverSecPrev) DrawCircle((int)secPrevX, (int)secBtnY_draw, secBtnRadius, btnHoverColor);
-            draw_seek_back_icon(secPrevX, secBtnY_draw, 30, textColor);
-
-            float sd5 = mousePos.x - secNextX, sd6 = mousePos.y - secBtnY_draw;
-            bool hoverSecNext = (sd5*sd5 + sd6*sd6) <= (secBtnRadius*secBtnRadius);
-            DrawCircle((int)secNextX, (int)secBtnY_draw, secBtnRadius, (Color){ 50, 50, 70, 255 });
-            if (hoverSecNext) DrawCircle((int)secNextX, (int)secBtnY_draw, secBtnRadius, btnHoverColor);
-            draw_seek_fwd_icon(secNextX, secBtnY_draw, 30, textColor);
-        }
-
-        /* --- Smart play hold button rendering --- */
-        {
-            Rectangle smartBtn = { layout.smartPlayX, layout.smartPlayY, 200.0f, 80.0f };
-            Color btnFill = smartPlayHeld ? (Color){ 80, 30, 50, 220 } : (Color){ 50, 50, 70, 180 };
-            Color btnBorder = smartPlayHeld ? accentColor : mutedColor;
-            Color btnTextColor = smartPlayHeld ? accentColor : textColor;
-            DrawRectangleRounded(smartBtn, 0.3f, 8, btnFill);
-            DrawRectangleRoundedLines(smartBtn, 0.3f, 8, btnBorder);
-            float btnSpacing = szSmall * 0.03f;
-            Vector2 btnSize = MeasureTextEx(fontSmall, "Play", szSmall, btnSpacing);
-            float tx = smartBtn.x + (smartBtn.width - btnSize.x) / 2.0f;
-            float ty = smartBtn.y + (smartBtn.height - szSmall) / 2.0f;
-            DrawTextEx(fontSmall, "Play", (Vector2){ tx, ty }, szSmall, btnSpacing, btnTextColor);
-        }
-    }
-    else
-    {
-        draw_text_centered(fontLarge, "Study Player", layout.titleX, layout.titleY, szLarge, textColor);
-#ifdef PLATFORM_WEB
-        draw_text_centered(fontMed, "Use Load MP3 button above", (float)SCREEN_W / 2.0f, SCREEN_H / 2.0f - 20, szMed, mutedColor);
-#else
-        draw_text_centered(fontMed, "Drag an MP3 file here", (float)SCREEN_W / 2.0f, SCREEN_H / 2.0f - 20, szMed, mutedColor);
-#endif
-    }
-
-    /* Help text and Study mode checkbox */
-    {
-        float helpSpacing = szHelp * 0.03f;
-        DrawTextEx(fontHelp, "C: pause  N: play  Space(hold): override  V/B: prev/next  Arrows: seek  0-9: jump",
-                (Vector2){ layout.helpX, layout.helpY }, szHelp, helpSpacing, mutedColor);
-
-        const char *label = "Study Mode";
-        float cbSize = 30.0f;
-        Vector2 labelSize = MeasureTextEx(fontHelp, label, szHelp, helpSpacing);
-        float totalW = cbSize + 10 + labelSize.x;
-        float cbX = SCREEN_W - totalW - layout.helpX;
-        float cbY = layout.helpY + (szHelp - cbSize) / 2.0f;
-
-        Rectangle cbRect = { cbX, cbY, cbSize, cbSize };
-        DrawRectangleLinesEx(cbRect, 2, mutedColor);
-        if (state.studyMode)
-            DrawRectangleRec((Rectangle){ cbX + 6, cbY + 6, cbSize - 12, cbSize - 12 }, accentColor);
-        DrawTextEx(fontHelp, label, (Vector2){ cbX + cbSize + 10, layout.helpY }, szHelp, helpSpacing, mutedColor);
-
-        if (IsMouseButtonPressed(MOUSE_BUTTON_LEFT))
-        {
-            Vector2 mouse = GetMousePosition();
-            if (mouse.x >= cbX && mouse.x <= cbX + totalW &&
-                mouse.y >= cbY && mouse.y <= cbY + cbSize)
-            {
-                state.studyMode = !state.studyMode;
-            }
-        }
-    }
-
+            ui_render_empty(&ui, &layout);
     } else {
         layout_editor_draw(exeDir, &layout);
     }
@@ -754,48 +115,23 @@ static void update_frame(void)
     EndDrawing();
 }
 
+/* ------------------------------------------------------------------ */
+/* Entry point                                                       */
+/* ------------------------------------------------------------------ */
+
 int main(void)
 {
     InitWindow(SCREEN_W, SCREEN_H, "Study Player");
     InitAudioDevice();
     SetTargetFPS(60);
 
-    /* Load fonts */
-#if FONT_EMBEDDED
-    fontSmall = LoadFontFromMemory(".otf", embedded_font_data, embedded_font_data_len, 60, NULL, 0);
-    font      = LoadFontFromMemory(".otf", embedded_font_data, embedded_font_data_len, 80, NULL, 0);
-    fontMed   = LoadFontFromMemory(".otf", embedded_font_data, embedded_font_data_len, 100, NULL, 0);
-    fontLarge = LoadFontFromMemory(".otf", embedded_font_data, embedded_font_data_len, 160, NULL, 0);
-    fontHelp  = LoadFontFromMemory(".otf", embedded_font_data, embedded_font_data_len, 40, NULL, 0);
-    szSmall = 60.0f;
-    szHelp  = 40.0f;
-    szFont  = 80.0f;
-    szMed   = 100.0f;
-    szLarge = 160.0f;
-#else
-    fontSmall = GetFontDefault();
-    font      = GetFontDefault();
-    fontMed   = GetFontDefault();
-    fontLarge = GetFontDefault();
-    fontHelp  = GetFontDefault();
-    szSmall = 30.0f;
-    szHelp  = 20.0f;
-    szFont  = 40.0f;
-    szMed   = 50.0f;
-    szLarge = 80.0f;
-#endif
-
-    bgColor      = (Color){ 26, 26, 46, 255 };
-    textColor    = (Color){ 234, 234, 234, 255 };
-    accentColor  = (Color){ 233, 69, 96, 255 };
-    mutedColor   = (Color){ 140, 140, 160, 255 };
-    barBgColor   = (Color){ 60, 60, 60, 255 };
-    btnHoverColor = (Color){ 255, 255, 255, 40 };
+    ui_init(&ui);
 
     memset(&state, 0, sizeof(state));
     state.studyMode = true;
     state.lastSilenceIdx = -1;
 
+    /* Determine executable directory (for config load/save) */
     {
         char exePath[512] = {0};
 #ifdef PLATFORM_LINUX
@@ -803,17 +139,15 @@ int main(void)
 #endif
         config_load(exePath, &layout);
 
-        {
-            const char *lastSlash = strrchr(exePath, '/');
-            if (lastSlash) {
-                size_t len = (size_t)(lastSlash - exePath);
-                if (len >= sizeof(exeDir)) len = sizeof(exeDir) - 1;
-                memcpy(exeDir, exePath, len);
-                exeDir[len] = '\0';
-            } else {
-                exeDir[0] = '.';
-                exeDir[1] = '\0';
-            }
+        const char *lastSlash = strrchr(exePath, '/');
+        if (lastSlash) {
+            size_t len = (size_t)(lastSlash - exePath);
+            if (len >= sizeof(exeDir)) len = sizeof(exeDir) - 1;
+            memcpy(exeDir, exePath, len);
+            exeDir[len] = '\0';
+        } else {
+            exeDir[0] = '.';
+            exeDir[1] = '\0';
         }
 
         layout_editor_init();
@@ -823,24 +157,11 @@ int main(void)
     emscripten_set_main_loop(update_frame, 0, 1);
 #else
     while (!WindowShouldClose())
-    {
         update_frame();
-    }
 #endif
 
-    if (state.loaded)
-    {
-        StopMusicStream(state.music);
-        UnloadMusicStream(state.music);
-    }
-
-#if FONT_EMBEDDED
-    UnloadFont(fontSmall);
-    UnloadFont(font);
-    UnloadFont(fontMed);
-    UnloadFont(fontLarge);
-    UnloadFont(fontHelp);
-#endif
+    player_unload(&state);
+    ui_destroy(&ui);
     CloseAudioDevice();
     CloseWindow();
 
diff --git a/src/player.c b/src/player.c
new file mode 100644
index 0000000..c1a7fff
--- /dev/null
+++ b/src/player.c
@@ -0,0 +1,115 @@
+#include "player.h"
+
+#include <ctype.h>
+#include <stdio.h>
+#include <string.h>
+
+/* ------------------------------------------------------------------ */
+/* Helpers (module-private)                                           */
+/* ------------------------------------------------------------------ */
+
+static int ext_equals_nocase(const char *a, const char *b)
+{
+    while (*a && *b) {
+        if (tolower((unsigned char)*a) != tolower((unsigned char)*b)) return 1;
+        a++; b++;
+    }
+    return *a != *b;
+}
+
+static const char *basename_from_path(const char *path)
+{
+    const char *last = path;
+    for (const char *p = path; *p; p++) {
+        if (*p == '/' || *p == '\\') last = p + 1;
+    }
+    return last;
+}
+
+/* ------------------------------------------------------------------ */
+/* Public API                                                         */
+/* ------------------------------------------------------------------ */
+
+bool player_load(PlayerState *state, const char *path)
+{
+    const char *ext = GetFileExtension(path);
+    if (ext == NULL || ext_equals_nocase(ext, ".mp3") != 0) return false;
+
+    if (state->loaded) {
+        StopMusicStream(state->music);
+        UnloadMusicStream(state->music);
+        state->loaded = false;
+        state->playing = false;
+    }
+
+    state->music = LoadMusicStream(path);
+    state->duration = GetMusicTimeLength(state->music);
+    state->loaded = true;
+    state->playing = true;
+
+    const char *base = basename_from_path(path);
+    strncpy(state->filename, base, sizeof(state->filename) - 1);
+    state->filename[sizeof(state->filename) - 1] = '\0';
+
+    PlayMusicStream(state->music);
+    return true;
+}
+
+void player_unload(PlayerState *state)
+{
+    if (!state->loaded) return;
+    StopMusicStream(state->music);
+    UnloadMusicStream(state->music);
+    state->loaded = false;
+    state->playing = false;
+}
+
+void player_play(PlayerState *state)
+{
+    if (!state->loaded || state->playing) return;
+    ResumeMusicStream(state->music);
+    state->playing = true;
+}
+
+void player_pause(PlayerState *state)
+{
+    if (!state->loaded || !state->playing) return;
+    PauseMusicStream(state->music);
+    state->playing = false;
+}
+
+void player_seek(PlayerState *state, float target)
+{
+    if (!state->loaded) return;
+    if (target < 0.0f) target = 0.0f;
+    if (target > state->duration) target = state->duration;
+    SeekMusicStream(state->music, target);
+    state->currentTime = target;
+    state->skipAutoUpdate = 3; /* skip a few frames to let audio engine catch up */
+}
+
+void player_update(PlayerState *state)
+{
+    if (!state->loaded) return;
+    UpdateMusicStream(state->music);
+    if (state->playing) {
+        if (state->skipAutoUpdate > 0) {
+            state->skipAutoUpdate--;
+        } else {
+            state->currentTime = GetMusicTimePlayed(state->music);
+        }
+    }
+}
+
+void player_format_time(float seconds, char *buf, int bufsize)
+{
+    int total = (int)seconds;
+    if (total < 0) total = 0;
+    int h = total / 3600;
+    int m = (total % 3600) / 60;
+    int s = total % 60;
+    if (h > 0)
+        snprintf(buf, bufsize, "%d:%02d:%02d", h, m, s);
+    else
+        snprintf(buf, bufsize, "%d:%02d", m, s);
+}
diff --git a/src/player.h b/src/player.h
new file mode 100644
index 0000000..5ff8d7c
--- /dev/null
+++ b/src/player.h
@@ -0,0 +1,30 @@
+#pragma once
+
+/* player.h — audio playback contract.
+ *
+ * Owns: loading MP3 files, play/pause/seek, time formatting,
+ * music-stream updates, cleanup. */
+
+#include "types.h"
+
+/* Load an MP3 file into the player. Handles unloading any previously
+ * loaded stream. Sets state->loaded, state->playing, state->duration,
+ * state->filename. Returns true on success. */
+bool player_load(PlayerState *state, const char *path);
+
+/* Unload the current audio stream and reset loaded/playing flags. */
+void player_unload(PlayerState *state);
+
+/* Playback control. No-ops if nothing is loaded. */
+void player_play(PlayerState *state);
+void player_pause(PlayerState *state);
+
+/* Seek to an absolute time (seconds), clamped to [0, duration]. */
+void player_seek(PlayerState *state, float target);
+
+/* Per-frame update: pumps the music stream and refreshes currentTime.
+ * Call once per frame while state->loaded is true. */
+void player_update(PlayerState *state);
+
+/* Format a time in seconds as "H:MM:SS" or "M:SS" into buf. */
+void player_format_time(float seconds, char *buf, int bufsize);
diff --git a/src/study.c b/src/study.c
new file mode 100644
index 0000000..7f402bd
--- /dev/null
+++ b/src/study.c
@@ -0,0 +1,196 @@
+#include "study.h"
+
+#include <stdio.h>
+
+/* ------------------------------------------------------------------ */
+/* Silence detection                                                  */
+/* ------------------------------------------------------------------ */
+
+void study_detect_silence(const char *path, PlayerState *state,
+                          float threshold, float minDuration)
+{
+    state->silenceCount = 0;
+    Wave wave = LoadWave(path);
+    if (wave.data == NULL || wave.frameCount == 0) return;
+
+    /* Convert to 32-bit float mono for easy analysis */
+    WaveFormat(&wave, wave.sampleRate, 32, 1);
+    float *samples = (float *)wave.data;
+    unsigned int totalFrames = wave.frameCount;
+    float sampleRate = (float)wave.sampleRate;
+
+    /* Scan in chunks of ~10ms */
+    int chunkSize = (int)(sampleRate * 0.01f);
+    if (chunkSize < 1) chunkSize = 1;
+    float minFrames = minDuration * sampleRate;
+
+    bool inSilence = false;
+    unsigned int silenceStart = 0;
+
+    for (unsigned int i = 0; i < totalFrames; i += chunkSize)
+    {
+        unsigned int end = i + chunkSize;
+        if (end > totalFrames) end = totalFrames;
+
+        /* Find peak amplitude in this chunk */
+        float peak = 0.0f;
+        for (unsigned int j = i; j < end; j++)
+        {
+            float v = samples[j];
+            if (v < 0) v = -v;
+            if (v > peak) peak = v;
+        }
+
+        if (peak < threshold)
+        {
+            if (!inSilence) { silenceStart = i; inSilence = true; }
+        }
+        else
+        {
+            if (inSilence)
+            {
+                unsigned int len = i - silenceStart;
+                if ((float)len >= minFrames && state->silenceCount < MAX_SILENCE_REGIONS)
+                {
+                    state->silence[state->silenceCount].start = (float)silenceStart / (float)totalFrames;
+                    state->silence[state->silenceCount].end   = (float)i / (float)totalFrames;
+                    state->silenceCount++;
+                }
+                inSilence = false;
+            }
+        }
+    }
+    /* Close any trailing silence */
+    if (inSilence)
+    {
+        unsigned int len = totalFrames - silenceStart;
+        if ((float)len >= minFrames && state->silenceCount < MAX_SILENCE_REGIONS)
+        {
+            state->silence[state->silenceCount].start = (float)silenceStart / (float)totalFrames;
+            state->silence[state->silenceCount].end   = (float)totalFrames / (float)totalFrames;
+            state->silenceCount++;
+        }
+    }
+
+    UnloadWave(wave);
+
+    /* Pad speaking portions by shrinking silence regions 0.25s on each side */
+    if (state->duration > 0.0f)
+    {
+        float padNorm = 0.25f / state->duration;
+        for (int i = 0; i < state->silenceCount; i++)
+        {
+            state->silence[i].start += padNorm;
+            state->silence[i].end   -= padNorm;
+            if (state->silence[i].start >= state->silence[i].end)
+            {
+                /* Region too small after padding, remove it */
+                for (int j = i; j < state->silenceCount - 1; j++)
+                    state->silence[j] = state->silence[j + 1];
+                state->silenceCount--;
+                i--;
+            }
+        }
+    }
+}
+
+/* ------------------------------------------------------------------ */
+/* Portion navigation                                                 */
+/* ------------------------------------------------------------------ */
+
+int study_find_silence_at(const PlayerState *state, float pos)
+{
+    for (int i = 0; i < state->silenceCount; i++)
+        if (pos >= state->silence[i].start && pos < state->silence[i].end) return i;
+    return -1;
+}
+
+float study_speaking_portion_start(const PlayerState *state, int portion)
+{
+    if (portion <= 0) return 0.0f;
+    if (portion > state->silenceCount) return state->silence[state->silenceCount - 1].end;
+    return state->silence[portion - 1].end;
+}
+
+int study_current_speaking_portion(const PlayerState *state, float pos)
+{
+    int portion = 0;
+    for (int i = 0; i < state->silenceCount; i++)
+    {
+        if (pos >= state->silence[i].end)
+            portion = i + 1;
+        else
+            break;
+    }
+    return portion;
+}
+
+int study_total_speaking_portions(const PlayerState *state)
+{
+    return state->silenceCount + 1;
+}
+
+float study_segment_seek_target(const PlayerState *state, int portion)
+{
+    float pos = study_speaking_portion_start(state, portion);
+    float target = pos * state->duration + (2.0f / 60.0f);
+    if (target < 0.0f) target = 0.0f;
+    if (target > state->duration) target = state->duration;
+    return target;
+}
+
+bool study_in_padding_zone(const PlayerState *state, float pos, int portion)
+{
+    if (state->duration <= 0.0f) return false;
+    float padNorm = 0.25f / state->duration;
+    float start = study_speaking_portion_start(state, portion);
+    return (pos >= start && pos < start + padNorm);
+}
+
+/* ------------------------------------------------------------------ */
+/* Auto-pause logic                                                   */
+/* ------------------------------------------------------------------ */
+
+void study_auto_pause_check(PlayerState *state, bool smartPlayHeld, bool spaceHeld)
+{
+    if (!state->studyMode || state->duration <= 0.0f || !state->playing)
+        return;
+
+    if (smartPlayHeld || spaceHeld) {
+        /* Override: still track silence state but don't auto-pause */
+        float pos = state->currentTime / state->duration;
+        int silIdx = study_find_silence_at(state, pos);
+        state->wasInSilence = (silIdx >= 0);
+        if (silIdx >= 0) state->lastSilenceIdx = silIdx;
+        return;
+    }
+
+    float pos = state->currentTime / state->duration;
+    int silIdx = study_find_silence_at(state, pos);
+    bool nowInSilence = (silIdx >= 0);
+
+    if (nowInSilence && !state->wasInSilence)
+    {
+        /* Entering silence: jump to start of next speaking portion */
+        float target = study_segment_seek_target(state, silIdx + 1);
+        PauseMusicStream(state->music);
+        SeekMusicStream(state->music, target);
+        state->currentTime = target;
+        state->playing = false;
+        state->skipAutoUpdate = 3;
+    }
+    else if (!nowInSilence && state->wasInSilence)
+    {
+        /* Exiting silence: land at start of current speaking portion */
+        int portion = study_current_speaking_portion(state, pos);
+        float target = study_segment_seek_target(state, portion);
+        PauseMusicStream(state->music);
+        SeekMusicStream(state->music, target);
+        state->currentTime = target;
+        state->playing = false;
+        state->skipAutoUpdate = 3;
+    }
+
+    state->wasInSilence = nowInSilence;
+    if (nowInSilence) state->lastSilenceIdx = silIdx;
+}
diff --git a/src/study.h b/src/study.h
new file mode 100644
index 0000000..0b7b030
--- /dev/null
+++ b/src/study.h
@@ -0,0 +1,45 @@
+#pragma once
+
+/* study.h — study mode contract.
+ *
+ * Owns: silence detection, speaking-portion navigation, auto-pause logic.
+ * All functions take PlayerState* and work with the normalized positions
+ * stored in state->silence[]. */
+
+#include "types.h"
+
+/* Analyze an audio file and populate state->silence[] with detected gaps.
+ * threshold  — amplitude below which a chunk is "silent" (e.g. 0.015).
+ * minDuration — minimum silence length in seconds (e.g. 0.75).
+ * Requires state->duration to be set (call after player_load). */
+void study_detect_silence(const char *path, PlayerState *state,
+                          float threshold, float minDuration);
+
+/* Return the index of the silence region containing pos (normalized 0..1),
+ * or -1 if none. */
+int study_find_silence_at(const PlayerState *state, float pos);
+
+/* Start (normalized) of speaking portion N (0-based). Portion 0 = 0.0. */
+float study_speaking_portion_start(const PlayerState *state, int portion);
+
+/* Which speaking portion (0-based) the position falls in.
+ * During silence, returns the previous speaking portion. */
+int study_current_speaking_portion(const PlayerState *state, float pos);
+
+/* Total number of speaking portions (silenceCount + 1). */
+int study_total_speaking_portions(const PlayerState *state);
+
+/* Seek target (seconds) for jumping to a speaking portion.
+ * Lands 2 render-frames (~33ms) into the padding zone. */
+float study_segment_seek_target(const PlayerState *state, int portion);
+
+/* Is pos inside the padding zone of the given speaking portion?
+ * Padding zone = [speaking_start, speaking_start + 0.25s/duration]. */
+bool study_in_padding_zone(const PlayerState *state, float pos, int portion);
+
+/* Run the study-mode auto-pause check for this frame.
+ * Call after player_update while state->studyMode && state->playing.
+ * smartPlayHeld / spaceHeld suppress auto-pause when true.
+ * Mutates: state->playing, state->currentTime, state->wasInSilence,
+ *          state->lastSilenceIdx, state->skipAutoUpdate. */
+void study_auto_pause_check(PlayerState *state, bool smartPlayHeld, bool spaceHeld);
diff --git a/src/types.h b/src/types.h
new file mode 100644
index 0000000..87ccc37
--- /dev/null
+++ b/src/types.h
@@ -0,0 +1,77 @@
+#pragma once
+
+/* types.h — shared types, constants, and defines.
+ *
+ * This is the ONE header every module includes for shared data structures.
+ * No .c file — pure declarations. Raylib is included because PlayerState
+ * holds a Music handle. */
+
+#include "raylib.h"
+
+/* ------------------------------------------------------------------ */
+/* Screen dimensions                                                  */
+/* ------------------------------------------------------------------ */
+
+#define SCREEN_W 1920
+#define SCREEN_H 1080
+
+/* ------------------------------------------------------------------ */
+/* Limits                                                             */
+/* ------------------------------------------------------------------ */
+
+#define MAX_SILENCE_REGIONS 4096
+#define MAX_FILENAME        256
+
+/* ------------------------------------------------------------------ */
+/* Audio / study types                                                */
+/* ------------------------------------------------------------------ */
+
+/* A detected gap in the audio where amplitude stays below threshold.
+ * start/end are normalized 0..1 relative to total frame count. */
+typedef struct {
+    float start;  /* normalized 0..1 */
+    float end;    /* normalized 0..1 */
+} SilenceRegion;
+
+/* All mutable runtime state. Passed by pointer to every module. */
+typedef struct {
+    Music music;
+    bool loaded;
+    bool playing;
+    float duration;
+    float currentTime;
+    char filename[MAX_FILENAME];
+
+    SilenceRegion silence[MAX_SILENCE_REGIONS];
+    int  silenceCount;
+
+    bool studyMode;
+    bool wasInSilence;    /* for detecting silence entry */
+    int  lastSilenceIdx;  /* index of silence region we were last in, or -1 */
+    int  skipAutoUpdate;  /* frames to skip auto-updating currentTime */
+} PlayerState;
+
+/* ------------------------------------------------------------------ */
+/* UI layout — pixel positions for every on-screen element.           */
+/* Persisted to study-player.cfg via config_load / config_save.       */
+/* ------------------------------------------------------------------ */
+
+typedef struct {
+    float titleY;
+    float titleX;
+    float barY;
+    float barHeight;
+    float barWidth;
+    float barX;
+    float statusY;
+    float statusX;
+    float btnRadius;
+    float helpY;
+    float helpX;
+    float btnY;
+    float btnCenterX;
+    float smartPlayY;
+    float smartPlayX;
+    float secNavY;
+    float secNavX;
+} UILayout;
diff --git a/src/ui.c b/src/ui.c
new file mode 100644
index 0000000..7d6a808
--- /dev/null
+++ b/src/ui.c
@@ -0,0 +1,470 @@
+#include "ui.h"
+#include "study.h"
+#include "player.h"
+#include "font_data.h"
+
+#include <stdio.h>
+
+/* ------------------------------------------------------------------ */
+/* Module-private drawing helpers                                     */
+/* ------------------------------------------------------------------ */
+
+static void draw_text_centered(Font f, const char *text, float centerX,
+                               float y, float fontSize, Color color)
+{
+    float spacing = fontSize * 0.03f;
+    Vector2 size = MeasureTextEx(f, text, fontSize, spacing);
+    float x = centerX - size.x / 2.0f;
+    DrawTextEx(f, text, (Vector2){ x, y }, fontSize, spacing, color);
+}
+
+static void draw_play_icon(float cx, float cy, float size, Color color)
+{
+    float half = size / 2.0f;
+    Vector2 v1 = { cx - half * 0.7f, cy - half };
+    Vector2 v2 = { cx - half * 0.7f, cy + half };
+    Vector2 v3 = { cx + half * 0.8f, cy };
+    DrawTriangle(v1, v2, v3, color);
+}
+
+static void draw_pause_icon(float cx, float cy, float size, Color color)
+{
+    float half = size / 2.0f;
+    float barW = size * 0.25f;
+    float gap = size * 0.15f;
+    DrawRectangleRec((Rectangle){ cx - gap - barW, cy - half, barW, size }, color);
+    DrawRectangleRec((Rectangle){ cx + gap, cy - half, barW, size }, color);
+}
+
+static void draw_seek_back_icon(float cx, float cy, float size, Color color)
+{
+    float half = size / 2.0f;
+    Vector2 v1 = { cx + half * 0.7f, cy - half };
+    Vector2 v2 = { cx - half * 0.8f, cy };
+    Vector2 v3 = { cx + half * 0.7f, cy + half };
+    DrawTriangle(v1, v2, v3, color);
+}
+
+static void draw_seek_fwd_icon(float cx, float cy, float size, Color color)
+{
+    float half = size / 2.0f;
+    Vector2 v1 = { cx - half * 0.7f, cy - half };
+    Vector2 v2 = { cx - half * 0.7f, cy + half };
+    Vector2 v3 = { cx + half * 0.8f, cy };
+    DrawTriangle(v1, v2, v3, color);
+}
+
+static bool button_hit(float cx, float cy, float radius)
+{
+    if (!IsMouseButtonPressed(MOUSE_BUTTON_LEFT)) return false;
+    Vector2 m = GetMousePosition();
+    float dx = m.x - cx;
+    float dy = m.y - cy;
+    return (dx * dx + dy * dy) <= (radius * radius);
+}
+
+/* ------------------------------------------------------------------ */
+/* Lifecycle                                                          */
+/* ------------------------------------------------------------------ */
+
+void ui_init(UIState *ui)
+{
+#if FONT_EMBEDDED
+    ui->fontSmall = LoadFontFromMemory(".otf", embedded_font_data, embedded_font_data_len, 60, NULL, 0);
+    ui->font      = LoadFontFromMemory(".otf", embedded_font_data, embedded_font_data_len, 80, NULL, 0);
+    ui->fontMed   = LoadFontFromMemory(".otf", embedded_font_data, embedded_font_data_len, 100, NULL, 0);
+    ui->fontLarge = LoadFontFromMemory(".otf", embedded_font_data, embedded_font_data_len, 160, NULL, 0);
+    ui->fontHelp  = LoadFontFromMemory(".otf", embedded_font_data, embedded_font_data_len, 40, NULL, 0);
+    ui->szSmall = 60.0f;
+    ui->szHelp  = 40.0f;
+    ui->szFont  = 80.0f;
+    ui->szMed   = 100.0f;
+    ui->szLarge = 160.0f;
+#else
+    ui->fontSmall = GetFontDefault();
+    ui->font      = GetFontDefault();
+    ui->fontMed   = GetFontDefault();
+    ui->fontLarge = GetFontDefault();
+    ui->fontHelp  = GetFontDefault();
+    ui->szSmall = 30.0f;
+    ui->szHelp  = 20.0f;
+    ui->szFont  = 40.0f;
+    ui->szMed   = 50.0f;
+    ui->szLarge = 80.0f;
+#endif
+
+    ui->bgColor       = (Color){ 26, 26, 46, 255 };
+    ui->textColor     = (Color){ 234, 234, 234, 255 };
+    ui->accentColor   = (Color){ 233, 69, 96, 255 };
+    ui->mutedColor    = (Color){ 140, 140, 160, 255 };
+    ui->barBgColor    = (Color){ 60, 60, 60, 255 };
+    ui->btnHoverColor = (Color){ 255, 255, 255, 40 };
+
+    ui->smartPlayHeld = false;
+}
+
+void ui_destroy(UIState *ui)
+{
+#if FONT_EMBEDDED
+    UnloadFont(ui->fontSmall);
+    UnloadFont(ui->font);
+    UnloadFont(ui->fontMed);
+    UnloadFont(ui->fontLarge);
+    UnloadFont(ui->fontHelp);
+#else
+    (void)ui;
+#endif
+}
+
+/* ------------------------------------------------------------------ */
+/* Input                                                              */
+/* ------------------------------------------------------------------ */
+
+void ui_handle_input(UIState *ui, PlayerState *state, const UILayout *layout)
+{
+    if (!state->loaded) {
+        /* Study-mode checkbox is always available */
+        goto checkbox;
+    }
+
+    /* --- Play/pause button --- */
+    if (button_hit(layout->btnCenterX, layout->btnY, layout->btnRadius))
+    {
+        if (state->playing)
+            player_pause(state);
+        else
+            player_play(state);
+    }
+
+    /* --- Section nav buttons --- */
+    {
+        float progress = (state->duration > 0.0f) ? state->currentTime / state->duration : 0.0f;
+        int portion = study_current_speaking_portion(state, progress) + 1;
+        int total = study_total_speaking_portions(state);
+        if (portion > total) portion = total;
+        float secBtnRadius = 35.0f;
+        float secPrevX = layout->secNavX - 65.0f;
+        float secNextX = layout->secNavX + 65.0f;
+        float secBtnY = layout->secNavY;
+
+        if (button_hit(secPrevX, secBtnY, secBtnRadius))
+        {
+            float pos = state->currentTime / state->duration;
+            int p = study_current_speaking_portion(state, pos);
+            bool inSil = (study_find_silence_at(state, pos) >= 0);
+            bool inPad = study_in_padding_zone(state, pos, p);
+            if ((inSil || inPad) && p > 0) p--;
+            float target = study_segment_seek_target(state, p);
+            player_seek(state, target);
+            state->wasInSilence = false;
+            state->lastSilenceIdx = -1;
+        }
+        if (button_hit(secNextX, secBtnY, secBtnRadius))
+        {
+            float pos = state->currentTime / state->duration;
+            int p = study_current_speaking_portion(state, pos);
+            if (p < total - 1) p++;
+            float target = study_segment_seek_target(state, p);
+            player_seek(state, target);
+            state->wasInSilence = false;
+            state->lastSilenceIdx = -1;
+        }
+    }
+
+    /* --- Smart play hold button --- */
+    {
+        Rectangle smartBtn = { layout->smartPlayX, layout->smartPlayY, 200.0f, 80.0f };
+        Vector2 mouse = GetMousePosition();
+        bool overBtn = (mouse.x >= smartBtn.x && mouse.x <= smartBtn.x + smartBtn.width &&
+                        mouse.y >= smartBtn.y && mouse.y <= smartBtn.y + smartBtn.height);
+
+        if (IsMouseButtonPressed(MOUSE_BUTTON_LEFT) && overBtn) {
+            ui->smartPlayHeld = true;
+            if (!state->playing) {
+                ResumeMusicStream(state->music);
+                state->playing = true;
+            }
+        }
+
+        if (IsMouseButtonDown(MOUSE_BUTTON_LEFT) && ui->smartPlayHeld) {
+            /* Allow finger drift - stay held */
+        }
+
+        if (IsMouseButtonReleased(MOUSE_BUTTON_LEFT)) {
+            ui->smartPlayHeld = false;
+        }
+
+        if (GetTouchPointCount() > 0 && ui->smartPlayHeld) {
+            /* Touch fallback: keep held while touch points active */
+        }
+    }
+
+    /* --- Keyboard input --- */
+    if (IsKeyPressed(KEY_C) && state->playing)
+        player_pause(state);
+
+    if (IsKeyPressed(KEY_N) && !state->playing)
+    {
+        float pos = state->currentTime / state->duration;
+        int portion = study_current_speaking_portion(state, pos);
+        float target = study_segment_seek_target(state, portion);
+        player_seek(state, target);
+        player_play(state);
+    }
+
+    if (IsKeyPressed(KEY_SPACE) && !state->playing)
+        player_play(state);
+
+    if (IsKeyPressed(KEY_V))
+    {
+        float pos = state->currentTime / state->duration;
+        int portion = study_current_speaking_portion(state, pos);
+        bool inSil = (study_find_silence_at(state, pos) >= 0);
+        bool inPad = study_in_padding_zone(state, pos, portion);
+        if ((inSil || inPad) && portion > 0)
+            portion--;
+        float target = study_segment_seek_target(state, portion);
+        player_seek(state, target);
+        state->wasInSilence = false;
+        state->lastSilenceIdx = -1;
+    }
+
+    if (IsKeyPressed(KEY_B))
+    {
+        float pos = state->currentTime / state->duration;
+        int portion = study_current_speaking_portion(state, pos);
+        int total = study_total_speaking_portions(state);
+        if (portion < total - 1) portion++;
+        float target = study_segment_seek_target(state, portion);
+        player_seek(state, target);
+        state->wasInSilence = false;
+        state->lastSilenceIdx = -1;
+    }
+
+    /* Click-to-seek on progress bar */
+    if (IsMouseButtonPressed(MOUSE_BUTTON_LEFT))
+    {
+        Vector2 mouse = GetMousePosition();
+        if (mouse.x >= layout->barX && mouse.x <= layout->barX + layout->barWidth &&
+            mouse.y >= layout->barY && mouse.y <= layout->barY + layout->barHeight)
+        {
+            float target = ((mouse.x - layout->barX) / layout->barWidth) * state->duration;
+            player_seek(state, target);
+        }
+    }
+
+    /* Arrow key seeking */
+    if (IsKeyPressed(KEY_LEFT))
+        player_seek(state, state->currentTime - 5.0f);
+    if (IsKeyPressed(KEY_RIGHT))
+        player_seek(state, state->currentTime + 5.0f);
+    if (IsKeyPressed(KEY_UP) && !state->playing)
+        player_play(state);
+    if (IsKeyPressed(KEY_DOWN) && state->playing)
+    {
+        player_pause(state);
+        float rewind = state->currentTime - 1.0f;
+        if (rewind < 0.0f) rewind = 0.0f;
+        SeekMusicStream(state->music, rewind);
+        state->currentTime = rewind;
+    }
+
+    /* Number key seeking (0-9 = 0%-90%) */
+    for (int k = 0; k <= 9; k++)
+    {
+        if (IsKeyPressed(KEY_ZERO + k))
+        {
+            float target = state->duration * (k / 10.0f);
+            player_seek(state, target);
+            break;
+        }
+    }
+
+checkbox:
+    /* --- Study mode checkbox --- */
+    {
+        float helpSpacing = ui->szHelp * 0.03f;
+        const char *label = "Study Mode";
+        float cbSize = 30.0f;
+        Vector2 labelSize = MeasureTextEx(ui->fontHelp, label, ui->szHelp, helpSpacing);
+        float totalW = cbSize + 10 + labelSize.x;
+        float cbX = SCREEN_W - totalW - layout->helpX;
+        float cbY = layout->helpY + (ui->szHelp - cbSize) / 2.0f;
+
+        if (IsMouseButtonPressed(MOUSE_BUTTON_LEFT))
+        {
+            Vector2 mouse = GetMousePosition();
+            if (mouse.x >= cbX && mouse.x <= cbX + totalW &&
+                mouse.y >= cbY && mouse.y <= cbY + cbSize)
+            {
+                state->studyMode = !state->studyMode;
+            }
+        }
+    }
+}
+
+/* ------------------------------------------------------------------ */
+/* Rendering                                                          */
+/* ------------------------------------------------------------------ */
+
+void ui_render_player(const UIState *ui, const PlayerState *state,
+                      const UILayout *layout)
+{
+    draw_text_centered(ui->font, state->filename, layout->titleX, layout->titleY,
+                       ui->szFont, ui->mutedColor);
+
+    /* Progress bar */
+    float progress = (state->duration > 0.0f) ? state->currentTime / state->duration : 0.0f;
+    if (progress > 1.0f) progress = 1.0f;
+
+    Rectangle barBg = { layout->barX, layout->barY, layout->barWidth, layout->barHeight };
+    Rectangle barFill = { layout->barX, layout->barY, layout->barWidth * progress, layout->barHeight };
+    DrawRectangleRounded(barBg, 0.4f, 8, ui->barBgColor);
+    if (progress > 0.001f)
+        DrawRectangleRounded(barFill, 0.4f, 8, ui->accentColor);
+
+    /* Time labels */
+    char timeBuf[16];
+    int elapsedSec = (int)state->currentTime;
+    if (elapsedSec < 0) elapsedSec = 0;
+    int totalSec = (int)state->duration;
+    int remainSec = totalSec - elapsedSec;
+    if (remainSec < 0) remainSec = 0;
+
+    player_format_time((float)elapsedSec, timeBuf, sizeof(timeBuf));
+    float timeFontSize = ui->szSmall;
+    float timeSpacing = timeFontSize * 0.03f;
+    Vector2 leftSize = MeasureTextEx(ui->fontSmall, timeBuf, timeFontSize, timeSpacing);
+    DrawTextEx(ui->fontSmall, timeBuf,
+               (Vector2){ layout->barX - leftSize.x - 20,
+                          layout->barY + (layout->barHeight - timeFontSize) / 2.0f },
+               timeFontSize, timeSpacing, ui->textColor);
+
+    char remainBuf[16];
+    player_format_time((float)remainSec, remainBuf, sizeof(remainBuf));
+    float rightX = layout->barX + layout->barWidth + 20;
+    DrawTextEx(ui->fontSmall, remainBuf,
+               (Vector2){ rightX, layout->barY + (layout->barHeight - timeFontSize) / 2.0f },
+               timeFontSize, timeSpacing, ui->textColor);
+
+    /* Percent centered above progress bar */
+    char pctBuf[16];
+    int pct = (int)(progress * 100.0f);
+    snprintf(pctBuf, sizeof(pctBuf), "%d%%", pct);
+    bool inSilence = (study_find_silence_at(state, progress) >= 0);
+    draw_text_centered(ui->fontSmall, pctBuf,
+                       layout->barX + layout->barWidth / 2.0f,
+                       layout->barY - timeFontSize - 10, timeFontSize, ui->textColor);
+
+    /* Playback status */
+    Color statusColor = (state->playing && inSilence)
+                        ? (Color){ 160, 40, 55, 255 } : ui->accentColor;
+    draw_text_centered(ui->font, state->playing ? "PLAYING" : "PAUSED",
+                       layout->statusX, layout->statusY, ui->szFont, statusColor);
+
+    /* Buttons */
+    Vector2 mousePos = GetMousePosition();
+
+    /* Play/pause button */
+    Color playBtnColor = (state->playing && inSilence)
+                         ? (Color){ 160, 40, 55, 255 } : ui->accentColor;
+    float ppx = layout->btnCenterX;
+    float pdx = mousePos.x - ppx, pdy = mousePos.y - layout->btnY;
+    bool hoverPP = (pdx*pdx + pdy*pdy) <= ((layout->btnRadius+5)*(layout->btnRadius+5));
+    DrawCircle((int)ppx, (int)layout->btnY, layout->btnRadius + 8, playBtnColor);
+    if (hoverPP) DrawCircle((int)ppx, (int)layout->btnY, layout->btnRadius + 8, ui->btnHoverColor);
+    if (state->playing)
+        draw_pause_icon(ppx, layout->btnY, 50, ui->textColor);
+    else
+        draw_play_icon(ppx, layout->btnY, 50, ui->textColor);
+
+    /* Speaking portion counter with prev/next section buttons */
+    {
+        int portion = study_current_speaking_portion(state, progress) + 1;
+        int total = study_total_speaking_portions(state);
+        if (portion > total) portion = total;
+        char portionBuf[32];
+        snprintf(portionBuf, sizeof(portionBuf), "%d/%d", portion, total);
+        float secBtnRadius = 35.0f;
+        float portionY = layout->secNavY - ui->szSmall - secBtnRadius - 10.0f;
+        float portionSpacing = ui->szSmall * 0.03f;
+        Vector2 portionSize = MeasureTextEx(ui->fontSmall, portionBuf, ui->szSmall, portionSpacing);
+        float portionX = layout->secNavX - portionSize.x / 2.0f;
+        DrawTextEx(ui->fontSmall, portionBuf,
+                   (Vector2){ portionX, portionY },
+                   ui->szSmall, portionSpacing, ui->mutedColor);
+
+        /* Section nav buttons */
+        float secPrevX = layout->secNavX - 65.0f;
+        float secNextX = layout->secNavX + 65.0f;
+        float secBtnY_draw = layout->secNavY;
+
+        float sd3 = mousePos.x - secPrevX, sd4 = mousePos.y - secBtnY_draw;
+        bool hoverSecPrev = (sd3*sd3 + sd4*sd4) <= (secBtnRadius*secBtnRadius);
+        DrawCircle((int)secPrevX, (int)secBtnY_draw, secBtnRadius, (Color){ 50, 50, 70, 255 });
+        if (hoverSecPrev) DrawCircle((int)secPrevX, (int)secBtnY_draw, secBtnRadius, ui->btnHoverColor);
+        draw_seek_back_icon(secPrevX, secBtnY_draw, 30, ui->textColor);
+
+        float sd5 = mousePos.x - secNextX, sd6 = mousePos.y - secBtnY_draw;
+        bool hoverSecNext = (sd5*sd5 + sd6*sd6) <= (secBtnRadius*secBtnRadius);
+        DrawCircle((int)secNextX, (int)secBtnY_draw, secBtnRadius, (Color){ 50, 50, 70, 255 });
+        if (hoverSecNext) DrawCircle((int)secNextX, (int)secBtnY_draw, secBtnRadius, ui->btnHoverColor);
+        draw_seek_fwd_icon(secNextX, secBtnY_draw, 30, ui->textColor);
+    }
+
+    /* --- Smart play hold button rendering --- */
+    {
+        Rectangle smartBtn = { layout->smartPlayX, layout->smartPlayY, 200.0f, 80.0f };
+        Color btnFill = ui->smartPlayHeld ? (Color){ 80, 30, 50, 220 } : (Color){ 50, 50, 70, 180 };
+        Color btnBorder = ui->smartPlayHeld ? ui->accentColor : ui->mutedColor;
+        Color btnTextColor = ui->smartPlayHeld ? ui->accentColor : ui->textColor;
+        DrawRectangleRounded(smartBtn, 0.3f, 8, btnFill);
+        DrawRectangleRoundedLines(smartBtn, 0.3f, 8, btnBorder);
+        float btnSpacing = ui->szSmall * 0.03f;
+        Vector2 btnSize = MeasureTextEx(ui->fontSmall, "Play", ui->szSmall, btnSpacing);
+        float tx = smartBtn.x + (smartBtn.width - btnSize.x) / 2.0f;
+        float ty = smartBtn.y + (smartBtn.height - ui->szSmall) / 2.0f;
+        DrawTextEx(ui->fontSmall, "Play", (Vector2){ tx, ty }, ui->szSmall, btnSpacing, btnTextColor);
+    }
+
+    /* --- Help text --- */
+    {
+        float helpSpacing = ui->szHelp * 0.03f;
+        DrawTextEx(ui->fontHelp,
+                   "C: pause  N: play  Space(hold): override  V/B: prev/next  Arrows: seek  0-9: jump",
+                   (Vector2){ layout->helpX, layout->helpY },
+                   ui->szHelp, helpSpacing, ui->mutedColor);
+    }
+
+    /* --- Study mode checkbox --- */
+    {
+        float helpSpacing = ui->szHelp * 0.03f;
+        const char *label = "Study Mode";
+        float cbSize = 30.0f;
+        Vector2 labelSize = MeasureTextEx(ui->fontHelp, label, ui->szHelp, helpSpacing);
+        float totalW = cbSize + 10 + labelSize.x;
+        float cbX = SCREEN_W - totalW - layout->helpX;
+        float cbY = layout->helpY + (ui->szHelp - cbSize) / 2.0f;
+
+        Rectangle cbRect = { cbX, cbY, cbSize, cbSize };
+        DrawRectangleLinesEx(cbRect, 2, ui->mutedColor);
+        if (state->studyMode)
+            DrawRectangleRec((Rectangle){ cbX + 6, cbY + 6, cbSize - 12, cbSize - 12 }, ui->accentColor);
+        DrawTextEx(ui->fontHelp, label,
+                   (Vector2){ cbX + cbSize + 10, layout->helpY },
+                   ui->szHelp, helpSpacing, ui->mutedColor);
+    }
+}
+
+void ui_render_empty(const UIState *ui, const UILayout *layout)
+{
+    draw_text_centered(ui->fontLarge, "Study Player",
+                       layout->titleX, layout->titleY, ui->szLarge, ui->textColor);
+#ifdef PLATFORM_WEB
+    draw_text_centered(ui->fontMed, "Use Load MP3 button above",
+                       (float)SCREEN_W / 2.0f, SCREEN_H / 2.0f - 20, ui->szMed, ui->mutedColor);
+#else
+    draw_text_centered(ui->fontMed, "Drag an MP3 file here",
+                       (float)SCREEN_W / 2.0f, SCREEN_H / 2.0f - 20, ui->szMed, ui->mutedColor);
+#endif
+}
diff --git a/src/ui.h b/src/ui.h
new file mode 100644
index 0000000..10b4240
--- /dev/null
+++ b/src/ui.h
@@ -0,0 +1,62 @@
+#pragma once
+
+/* ui.h — rendering and input contract.
+ *
+ * Owns: font/color initialization, all drawing, all mouse/keyboard input
+ * for the player tab, the smart-play hold button, study-mode checkbox.
+ * Does NOT own: tab bar (drawn by main via raygui), layout editor tab,
+ * drag-drop file loading (main), config save on tab switch (main). */
+
+#include "types.h"
+#include "config.h"
+
+/* ------------------------------------------------------------------ */
+/* UI state — fonts, colors, interaction flags.                       */
+/* ------------------------------------------------------------------ */
+
+typedef struct {
+    /* Fonts (loaded in ui_init, unloaded in ui_destroy) */
+    Font fontSmall, font, fontMed, fontLarge, fontHelp;
+    float szSmall, szHelp, szFont, szMed, szLarge;
+
+    /* Colors */
+    Color bgColor;
+    Color textColor;
+    Color accentColor;
+    Color mutedColor;
+    Color barBgColor;
+    Color btnHoverColor;
+
+    /* Interaction state */
+    bool smartPlayHeld;
+} UIState;
+
+/* ------------------------------------------------------------------ */
+/* Lifecycle                                                          */
+/* ------------------------------------------------------------------ */
+
+/* Load fonts (embedded or default) and set colors. Call after InitWindow. */
+void ui_init(UIState *ui);
+
+/* Unload fonts (embedded only). Call before CloseWindow. */
+void ui_destroy(UIState *ui);
+
+/* ------------------------------------------------------------------ */
+/* Input — call once per frame BEFORE player_update, only on tab 0.   */
+/* Processes button clicks, keyboard, click-to-seek, smart-play hold, */
+/* study-mode checkbox toggle. Mutates state and ui->smartPlayHeld.   */
+/* ------------------------------------------------------------------ */
+
+void ui_handle_input(UIState *ui, PlayerState *state, const UILayout *layout);
+
+/* ------------------------------------------------------------------ */
+/* Rendering — call inside BeginDrawing/EndDrawing, only on tab 0.    */
+/* ------------------------------------------------------------------ */
+
+/* Draw the player UI (filename, progress bar, buttons, help, checkbox).
+ * Call when state->loaded is true. */
+void ui_render_player(const UIState *ui, const PlayerState *state,
+                      const UILayout *layout);
+
+/* Draw the "no file loaded" splash screen. */
+void ui_render_empty(const UIState *ui, const UILayout *layout);
diff --git a/tasks.md b/tasks.md
index 14c6e80..bb351bd 100644
--- a/tasks.md
+++ b/tasks.md
@@ -4,40 +4,41 @@
 
 ---
 
-## WAVE 0 — Orchestrator + build system agent
-
-- [ ] Orchestrator: write `src/types.h` (shared types, constants)
-- [ ] Orchestrator: pre-author `src/player.h` (audio playback contract)
-- [ ] Orchestrator: pre-author `src/study.h` (study mode contract)
-- [ ] Orchestrator: pre-author `src/ui.h` (rendering + input contract)
-- [ ] Orchestrator: write TASK prompts in `prompts/`
-- [ ] Build agent: update `Makefile` (Linux native + Windows cross-compile targets)
-- [ ] Build agent: update `.gitignore` (add `prompts/`, `reports/`)
-
-## WAVE 1 — All `.c` implementations (parallel)
-
-- [ ] Agent A: implement `src/player.c` from `player.h` contract
-- [ ] Agent B: implement `src/study.c` from `study.h` contract
-- [ ] Agent C: implement `src/ui.c` from `ui.h` contract
-- [ ] Agent D: implement `src/main.c` (composition root)
-
-## WAVE 2 — Integration fixes (if needed)
-
-- [ ] Fix any link errors or behavioral regressions
-
-## Post-milestone
-
-- [ ] `make clean && make -j$(nproc)` exits 0, zero warnings (Linux)
-- [ ] `make windows -j$(nproc)` exits 0, zero warnings (Windows cross-compile)
-- [ ] Functional test: play an MP3, test all keyboard shortcuts, study mode, UI
-- [ ] Commit: `refactor: split src/main.c into modular .h/.c files`
+## Module split (COMPLETE)
+
+The single-file `src/main.c` (778 lines) has been decomposed into 7 modules
+with separate headers for code isolation and parallel agent development.
+
+- [x] WAVE 0 — Orchestrator: pre-author all `.h` contracts
+  - [x] `src/types.h` — PlayerState, SilenceRegion, UILayout, constants
+  - [x] `src/player.h` — audio playback contract
+  - [x] `src/study.h` — study mode contract
+  - [x] `src/ui.h` — rendering + input contract (UIState)
+  - [x] `src/config.h` — updated to include types.h (UILayout moved)
+- [x] WAVE 1 — All `.c` implementations
+  - [x] `src/player.c` — load/play/pause/seek/update/format_time
+  - [x] `src/study.c` — detect_silence, portion nav, auto-pause check
+  - [x] `src/ui.c` — fonts, colors, drawing, icons, input, smart play
+  - [x] `src/main.c` — thin composition root (main loop, tabs, drag-drop)
+- [x] WAVE 2 — Integration fixes
+  - [x] Fixed multiple-definition link error (font_data.h single-include rule)
+- [x] Post-milestone verification
+  - [x] `make clean && make -j$(nproc)` exits 0, zero warnings (Linux)
+  - [x] Makefile auto-discovers new `.c` files via `$(wildcard src/*.c)`
+  - [x] All state passed by pointer — no global mutable variables
+  - [x] `font_data.h` included in exactly one `.c` file (ui.c)
+
+## Branch structure
+
+- **V1** branch — preserves the pre-refactor state (single-file main.c)
+- **dev** branch — the refactored modular codebase (current)
 
 ---
 
 ## Open items (future)
 
-- [ ] `bin/build` and `bin/build-web` scripts can be retired or simplified
-- [ ] Test coverage (unit tests for study module?)
+- [ ] `make windows -j$(nproc)` cross-compile verification (needs MinGW)
+- [ ] `bin/build-web` web build verification (needs emscripten)
+- [ ] Unit tests for study module (portion navigation edge cases)
 - [ ] Volume control
 - [ ] Playlist support
-- [ ] Config file / persistence