synced samples

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diff --git a/samples/04_physics_and_collisions/01_simple/app/main.rb b/samples/04_physics_and_collisions/01_simple/app/main.rb
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+++ b/samples/04_physics_and_collisions/01_simple/app/main.rb
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+=begin
+
+ Reminders:
+ - ARRAY#intersect_rect?: Returns true or false depending on if the two rectangles intersect.
+
+ - args.outputs.solids: An array. The values generate a solid.
+   The parameters are [X, Y, WIDTH, HEIGHT, RED, GREEN, BLUE]
+
+=end
+
+# This sample app shows collisions between two boxes.
+
+# Runs methods needed for game to run properly.
+def tick args
+  tick_instructions args, "Sample app shows how to move a square over time and determine collision."
+  defaults args
+  render args
+  calc args
+end
+
+# Sets default values.
+def defaults args
+  # These values represent the moving box.
+  args.state.moving_box_speed   = 10
+  args.state.moving_box_size    = 100
+  args.state.moving_box_dx    ||=  1
+  args.state.moving_box_dy    ||=  1
+  args.state.moving_box       ||= [0, 0, args.state.moving_box_size, args.state.moving_box_size] # moving_box_size is set as the width and height
+
+  # These values represent the center box.
+  args.state.center_box ||= [540, 260, 200, 200, 180]
+  args.state.center_box_collision ||= false # initially no collision
+end
+
+def render args
+  # If the game state denotes that a collision has occured,
+  # render a solid square, otherwise render a border instead.
+  if args.state.center_box_collision
+    args.outputs.solids << args.state.center_box
+  else
+    args.outputs.borders << args.state.center_box
+  end
+
+  # Then render the moving box.
+  args.outputs.solids << args.state.moving_box
+end
+
+# Generally in a pipeline for a game engine, you have rendering,
+# game simulation (calculation), and input processing.
+# This fuction represents the game simulation.
+def calc args
+  position_moving_box args
+  determine_collision_center_box args
+end
+
+# Changes the position of the moving box on the screen by multiplying the change in x (dx) and change in y (dy) by the speed,
+# and adding it to the current position.
+# dx and dy are positive if the box is moving right and up, respectively
+# dx and dy are negative if the box is moving left and down, respectively
+def position_moving_box args
+  args.state.moving_box.x += args.state.moving_box_dx * args.state.moving_box_speed
+  args.state.moving_box.y += args.state.moving_box_dy * args.state.moving_box_speed
+
+  # 1280x720 are the virtual pixels you work with (essentially 720p).
+  screen_width  = 1280
+  screen_height = 720
+
+  # Position of the box is denoted by the bottom left hand corner, in
+  # that case, we have to subtract the width of the box so that it stays
+  # in the scene (you can try deleting the subtraction to see how it
+  # impacts the box's movement).
+  if args.state.moving_box.x > screen_width - args.state.moving_box_size
+    args.state.moving_box_dx = -1 # moves left
+  elsif args.state.moving_box.x < 0
+    args.state.moving_box_dx =  1 # moves right
+  end
+
+  # Here, we're making sure the moving box remains within the vertical scope of the screen
+  if args.state.moving_box.y > screen_height - args.state.moving_box_size # if the box moves too high
+    args.state.moving_box_dy = -1 # moves down
+  elsif args.state.moving_box.y < 0 # if the box moves too low
+    args.state.moving_box_dy =  1 # moves up
+  end
+end
+
+def determine_collision_center_box args
+  # Collision is handled by the engine. You simply have to call the
+  # `intersect_rect?` function.
+  if args.state.moving_box.intersect_rect? args.state.center_box # if the two boxes intersect
+    args.state.center_box_collision = true # then a collision happened
+  else
+    args.state.center_box_collision = false # otherwise, no collision happened
+  end
+end
+
+def tick_instructions args, text, y = 715
+  return if args.state.key_event_occurred
+  if args.inputs.mouse.click ||
+     args.inputs.keyboard.directional_vector ||
+     args.inputs.keyboard.key_down.enter ||
+     args.inputs.keyboard.key_down.escape
+    args.state.key_event_occurred = true
+  end
+
+  args.outputs.debug << [0, y - 50, 1280, 60].solid
+  args.outputs.debug << [640, y, text, 1, 1, 255, 255, 255].label
+  args.outputs.debug << [640, y - 25, "(click to dismiss instructions)" , -2, 1, 255, 255, 255].label
+end
diff --git a/samples/04_physics_and_collisions/01_simple/license-for-sample.txt b/samples/04_physics_and_collisions/01_simple/license-for-sample.txt
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index 0000000..100dcec
--- /dev/null
+++ b/samples/04_physics_and_collisions/01_simple/license-for-sample.txt
@@ -0,0 +1,9 @@
+Copyright 2019 DragonRuby LLC
+
+MIT License
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.