Add Switches, Fire/Water Collision and Play Menu

* New doodads: Switches.
  * They come in four varieties: wall switch (background element, with
    "ON/OFF" text) and three side-profile switches for the floor, left
    or right walls.
  * On collision with the player, they flip their state from "OFF" to
    "ON" or vice versa. If the player walks away and then collides
    again, the switch flips again.
  * Can be used to open/close Electric Doors when turned on/off. Their
    default state is "off"
  * If a switch receives a power signal from another linked switch, it
    sets its own state to match. So, two "on/off" switches that are
    connected to a door AND to each other will both flip on/off when one
    of them flips.
* Update the Level Collision logic to support Decoration, Fire and Water
  pixel collisions.
  * Previously, ALL pixels in the level were acting as though solid.
  * Non-solid pixels don't count for collision detection, but their
    attributes (fire and water) are collected and returned.
* Updated the MenuScene to support loading a map file in Play Mode
  instead of Edit Mode. Updated the title screen menu to add a button
  for playing levels instead of editing them.
* Wrote some documentation.

dev-assets/doodads/build.sh

@@ -24,6 +24,23 @@ buttons() {
 	cd ..
 }
 
+switches() {
+	cd switches/
+
+	doodad convert -t "Switch" switch-off.png switch-on.png switch.doodad
+	doodad convert -t "Floor Switch" down-off.png down-on.png switch-down.doodad
+	doodad convert -t "Left Switch" left-off.png left-on.png switch-left.doodad
+	doodad convert -t "Right Switch" right-off.png right-on.png switch-right.doodad
+
+	doodad install-script switch.js switch.doodad
+	doodad install-script switch.js switch-down.doodad
+	doodad install-script switch.js switch-left.doodad
+	doodad install-script switch.js switch-right.doodad
+
+	cp *.doodad ../../../assets/doodads/
+	cd ..
+}
+
 doors() {
 	cd doors/
 
@@ -104,6 +121,7 @@ objects() {
 }
 
 buttons
+switches
 doors
 trapdoors
 azulians

dev-assets/doodads/doors/electric-door.js

@@ -23,8 +23,8 @@ function main() {
 			});
 		} else {
 			animating = true;
+			opened = false;
 			Self.PlayAnimation("close", function() {
-				opened = false;
 				animating = false;
 			})
 		}

dev-assets/doodads/switches/switch.js

@@ -0,0 +1,38 @@
+function main() {
+	console.log("%s initialized!", Self.Doodad.Title);
+
+	// Switch has two frames:
+	// 0: Off
+	// 1: On
+
+	var state = false;
+	var collide = false;
+
+	Message.Subscribe("power", function(powered) {
+		state = powered;
+		showState(state);
+	});
+
+	Events.OnCollide(function(e) {
+		if (collide === false) {
+			state = !state;
+			Message.Publish("power", state);
+			showState(state);
+
+			collide = true;
+		}
+	});
+
+	Events.OnLeave(function(e) {
+		collide = false;
+	});
+}
+
+// showState shows the on/off frame based on the boolean powered state.
+function showState(state) {
+	if (state) {
+		Self.ShowLayer(1);
+	} else {
+		Self.ShowLayer(0);
+	}
+}