/net/flashpunk/FP.as

package net.flashpunk 
{
	import flash.display.BitmapData;
	import flash.display.Sprite;
	import flash.display.Stage;
	import flash.geom.Matrix;
	import flash.geom.Point;
	import flash.geom.Rectangle;
	import flash.media.SoundMixer;
	import flash.media.SoundTransform;
	import flash.system.System;
	import flash.utils.ByteArray;
	import flash.utils.getTimer;
	
	import net.flashpunk.*;
	import net.flashpunk.debug.Console;
	import net.flashpunk.tweens.misc.Alarm;
	import net.flashpunk.tweens.misc.MultiVarTween;
	
	/**
	 * Static catch-all class used to access global properties and functions.
	 */
	public class FP 
	{
		/**
		 * The FlashPunk major version.
		 */
		public static const VERSION:String = "1.6";
		
		/**
		 * Width of the game.
		 */
		public static var width:uint;
		
		/**
		 * Height of the game.
		 */
		public static var height:uint;
		
		/**
		 * Half width of the game.
		 */
		public static var halfWidth:Number;
		
		/**
		 * Half height of the game.
		 */
		public static var halfHeight:Number;
		
		/**
		 * If the game is running at a fixed framerate.
		 */
		public static var fixed:Boolean;
		
		/**
		 * If times should be given in frames (as opposed to seconds).
		 * Default is true in fixed timestep mode and false in variable timestep mode.
		 */
		public static var timeInFrames:Boolean;
		
		/**
		 * The framerate assigned to the stage.
		 */
		public static var frameRate:Number;
		
		/**
		 * The framerate assigned to the stage.
		 */
		public static var assignedFrameRate:Number;
		
		/**
		 * Time elapsed since the last frame (in seconds).
		 */
		public static var elapsed:Number;
		
		/**
		 * Timescale applied to FP.elapsed.
		 */
		public static var rate:Number = 1;
		
		/**
		 * The Screen object, use to transform or offset the Screen.
		 */
		public static var screen:Screen;
		
		/**
		 * The current screen buffer, drawn to in the render loop.
		 */
		public static var buffer:BitmapData;
		
		/**
		 * A rectangle representing the size of the screen.
		 */
		public static var bounds:Rectangle;
		
		/**
		 * Point used to determine drawing offset in the render loop.
		 */
		public static var camera:Point = new Point;
		
		/**
		 * Global Tweener for tweening values across multiple worlds.
		 */
		public static var tweener:Tweener = new Tweener;
		
		/**
		 * If the game currently has input focus or not. Note: may not be correct initially.
		 */
		public static var focused:Boolean = true;
		
		/**
		 * The currently active World object. When you set this, the World is flagged
		 * to switch, but won't actually do so until the end of the current frame.
		 */
		public static function get world():World { return _world; }
		public static function set world(value:World):void
		{
			if (_world == value) return;
			_goto = value;
		}
		
		/**
		 * Sets the camera position.
		 * @param	x	X position.
		 * @param	y	Y position.
		 */
		public static function setCamera(x:Number = 0, y:Number = 0):void
		{
			camera.x = x;
			camera.y = y;
		}
		
		/**
		 * Resets the camera position.
		 */
		public static function resetCamera():void
		{
			camera.x = camera.y = 0;
		}
		
		/**
		 * Global volume factor for all sounds, a value from 0 to 1.
		 */
		public static function get volume():Number { return _volume; }
		public static function set volume(value:Number):void
		{
			if (value < 0) value = 0;
			if (_volume == value) return;
			_soundTransform.volume = _volume = value;
			SoundMixer.soundTransform = _soundTransform;
		}
		
		/**
		 * Global panning factor for all sounds, a value from -1 to 1.
		 */
		public static function get pan():Number { return _pan; }
		public static function set pan(value:Number):void
		{
			if (value < -1) value = -1;
			if (value > 1) value = 1;
			if (_pan == value) return;
			_soundTransform.pan = _pan = value;
			SoundMixer.soundTransform = _soundTransform;
		}
		
		/**
		 * Remove an element from an array
		 * @return	True if element existed and has been removed, false if element was not in array.
		 */
		public static function remove(array:*, toRemove:*):Boolean
		{
			var i:int = array.indexOf(toRemove);
			
			if (i >= 0) {
				array.splice(i, 1);
			
				return true;
			} else {
				return false;
			}
		}
		
		/**
		 * Randomly chooses and returns one of the provided values.
		 * @param	...objs		The Objects you want to randomly choose from. Can be ints, Numbers, Points, etc.
		 * @return	A randomly chosen one of the provided parameters.
		 */
		public static function choose(...objs):*
		{
			var c:* = (objs.length == 1 && (objs[0] is Array || objs[0] is Vector.<*>)) ? objs[0] : objs;
			return c[rand(c.length)];
		}
		
		/**
		 * Finds the sign of the provided value.
		 * @param	value		The Number to evaluate.
		 * @return	1 if value > 0, -1 if value < 0, and 0 when value == 0.
		 */
		public static function sign(value:Number):int
		{
			return value < 0 ? -1 : (value > 0 ? 1 : 0);
		}
		
		/**
		 * Approaches the value towards the target, by the specified amount, without overshooting the target.
		 * @param	value	The starting value.
		 * @param	target	The target that you want value to approach.
		 * @param	amount	How much you want the value to approach target by.
		 * @return	The new value.
		 */
		public static function approach(value:Number, target:Number, amount:Number):Number
		{
			return value < target ? (target < value + amount ? target : value + amount) : (target > value - amount ? target : value - amount);
		}
		
		/**
		 * Linear interpolation between two values.
		 * @param	a		First value.
		 * @param	b		Second value.
		 * @param	t		Interpolation factor.
		 * @return	When t=0, returns a. When t=1, returns b. When t=0.5, will return halfway between a and b. Etc.
		 */
		public static function lerp(a:Number, b:Number, t:Number = 1):Number
		{
			return a + (b - a) * t;
		}
		
		/**
		 * Linear interpolation between two colors.
		 * @param	fromColor		First color.
		 * @param	toColor			Second color.
		 * @param	t				Interpolation value. Clamped to the range [0, 1].
		 * return	RGB component-interpolated color value.
		 */
		public static function colorLerp(fromColor:uint, toColor:uint, t:Number = 1):uint
		{
			if (t <= 0) { return fromColor; }
			if (t >= 1) { return toColor; }
			var a:uint = fromColor >> 24 & 0xFF,
				r:uint = fromColor >> 16 & 0xFF,
				g:uint = fromColor >> 8 & 0xFF,
				b:uint = fromColor & 0xFF,
				dA: int = (toColor >> 24 & 0xFF) - a,
				dR: int = (toColor >> 16 & 0xFF) - r,
				dG: int = (toColor >> 8 & 0xFF) - g,
				dB: int = (toColor & 0xFF) - b;
			a += dA * t;
			r += dR * t;
			g += dG * t;
			b += dB * t;
			return a << 24 | r << 16 | g << 8 | b;
		}
		
		/**
		 * Steps the object towards a point.
		 * @param	object		Object to move (must have an x and y property).
		 * @param	x			X position to step towards.
		 * @param	y			Y position to step towards.
		 * @param	distance	The distance to step (will not overshoot target).
		 */
		public static function stepTowards(object:Object, x:Number, y:Number, distance:Number = 1):void
		{
			point.x = x - object.x;
			point.y = y - object.y;
			if (point.length <= distance)
			{
				object.x = x;
				object.y = y;
				return;
			}
			point.normalize(distance);
			object.x += point.x;
			object.y += point.y;
		}
		
		/**
		 * Anchors the object to a position.
		 * @param	object		The object to anchor.
		 * @param	anchor		The anchor object.
		 * @param	distance	The max distance object can be anchored to the anchor.
		 */
		public static function anchorTo(object:Object, anchor:Object, distance:Number = 0):void
		{
			point.x = object.x - anchor.x;
			point.y = object.y - anchor.y;
			if (point.length > distance) point.normalize(distance);
			object.x = anchor.x + point.x;
			object.y = anchor.y + point.y;
		}
		
		/**
		 * Finds the angle (in degrees) from point 1 to point 2.
		 * @param	x1		The first x-position.
		 * @param	y1		The first y-position.
		 * @param	x2		The second x-position.
		 * @param	y2		The second y-position.
		 * @return	The angle from (x1, y1) to (x2, y2).
		 */
		public static function angle(x1:Number, y1:Number, x2:Number, y2:Number):Number
		{
			var a:Number = Math.atan2(y2 - y1, x2 - x1) * DEG;
			return a < 0 ? a + 360 : a;
		}
		
		/**
		 * Sets the x/y values of the provided object to a vector of the specified angle and length.
		 * @param	object		The object whose x/y properties should be set.
		 * @param	angle		The angle of the vector, in degrees.
		 * @param	length		The distance to the vector from (0, 0).
		 * @param	x			X offset.
		 * @param	y			Y offset.
		 */
		public static function angleXY(object:Object, angle:Number, length:Number = 1, x:Number = 0, y:Number = 0):void
		{
			angle *= RAD;
			object.x = Math.cos(angle) * length + x;
			object.y = Math.sin(angle) * length + y;
		}
		
		/**
		 * Rotates the object around the anchor by the specified amount.
		 * @param	object		Object to rotate around the anchor.
		 * @param	anchor		Anchor to rotate around.
		 * @param	angle		The amount of degrees to rotate by.
		 */
		public static function rotateAround(object:Object, anchor:Object, angle:Number = 0, relative:Boolean = true):void
		{
			if (relative) angle += FP.angle(anchor.x, anchor.y, object.x, object.y);
			FP.angleXY(object, angle, FP.distance(anchor.x, anchor.y, object.x, object.y), anchor.x, anchor.y);
		}
		
		/**
		 * Gets the difference of two angles, wrapped around to the range -180 to 180.
		 * @param	a	First angle in degrees.
		 * @param	b	Second angle in degrees.
		 * @return	Difference in angles, wrapped around to the range -180 to 180.
		 */
		public static function angleDiff(a:Number, b:Number):Number
		{
			var diff:Number = b - a;

			while (diff > 180) { diff -= 360; }
			while (diff <= -180) { diff += 360; }

			return diff;
		}
		/**
		 * Find the distance between two points.
		 * @param	x1		The first x-position.
		 * @param	y1		The first y-position.
		 * @param	x2		The second x-position.
		 * @param	y2		The second y-position.
		 * @return	The distance.
		 */
		public static function distance(x1:Number, y1:Number, x2:Number = 0, y2:Number = 0):Number
		{
			return Math.sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1));
		}
		
		/**
		 * Find the distance between two rectangles. Will return 0 if the rectangles overlap.
		 * @param	x1		The x-position of the first rect.
		 * @param	y1		The y-position of the first rect.
		 * @param	w1		The width of the first rect.
		 * @param	h1		The height of the first rect.
		 * @param	x2		The x-position of the second rect.
		 * @param	y2		The y-position of the second rect.
		 * @param	w2		The width of the second rect.
		 * @param	h2		The height of the second rect.
		 * @return	The distance.
		 */
		public static function distanceRects(x1:Number, y1:Number, w1:Number, h1:Number, x2:Number, y2:Number, w2:Number, h2:Number):Number
		{
			if (x1 < x2 + w2 && x2 < x1 + w1)
			{
				if (y1 < y2 + h2 && y2 < y1 + h1) return 0;
				if (y1 > y2) return y1 - (y2 + h2);
				return y2 - (y1 + h1);
			}
			if (y1 < y2 + h2 && y2 < y1 + h1)
			{
				if (x1 > x2) return x1 - (x2 + w2);
				return x2 - (x1 + w1)
			}
			if (x1 > x2)
			{
				if (y1 > y2) return distance(x1, y1, (x2 + w2), (y2 + h2));
				return distance(x1, y1 + h1, x2 + w2, y2);
			}
			if (y1 > y2) return distance(x1 + w1, y1, x2, y2 + h2)
			return distance(x1 + w1, y1 + h1, x2, y2);
		}
		
		/**
		 * Find the distance between a point and a rectangle. Returns 0 if the point is within the rectangle.
		 * @param	px		The x-position of the point.
		 * @param	py		The y-position of the point.
		 * @param	rx		The x-position of the rect.
		 * @param	ry		The y-position of the rect.
		 * @param	rw		The width of the rect.
		 * @param	rh		The height of the rect.
		 * @return	The distance.
		 */
		public static function distanceRectPoint(px:Number, py:Number, rx:Number, ry:Number, rw:Number, rh:Number):Number
		{
			if (px >= rx && px <= rx + rw)
			{
				if (py >= ry && py <= ry + rh) return 0;
				if (py > ry) return py - (ry + rh);
				return ry - py;
			}
			if (py >= ry && py <= ry + rh)
			{
				if (px > rx) return px - (rx + rw);
				return rx - px;
			}
			if (px > rx)
			{
				if (py > ry) return distance(px, py, rx + rw, ry + rh);
				return distance(px, py, rx + rw, ry);
			}
			if (py > ry) return distance(px, py, rx, ry + rh)
			return distance(px, py, rx, ry);
		}
		
		/**
		 * Clamps the value within the minimum and maximum values.
		 * @param	value		The Number to evaluate.
		 * @param	min			The minimum range.
		 * @param	max			The maximum range.
		 * @return	The clamped value.
		 */
		public static function clamp(value:Number, min:Number, max:Number):Number
		{
			if (max > min)
			{
				value = value < max ? value : max;
				return value > min ? value : min;
			}
			value = value < min ? value : min;
			return value > max ? value : max;
		}
		
		/**
		 * Clamps the object inside the rectangle.
		 * @param	object		The object to clamp (must have an x and y property).
		 * @param	x			Rectangle's x.
		 * @param	y			Rectangle's y.
		 * @param	width		Rectangle's width.
		 * @param	height		Rectangle's height.
		 */
		public static function clampInRect(object:Object, x:Number, y:Number, width:Number, height:Number, padding:Number = 0):void
		{
			object.x = clamp(object.x, x + padding, x + width - padding);
			object.y = clamp(object.y, y + padding, y + height - padding);
		}
		
		/**
		 * Transfers a value from one scale to another scale. For example, scale(.5, 0, 1, 10, 20) == 15, and scale(3, 0, 5, 100, 0) == 40.
		 * @param	value		The value on the first scale.
		 * @param	min			The minimum range of the first scale.
		 * @param	max			The maximum range of the first scale.
		 * @param	min2		The minimum range of the second scale.
		 * @param	max2		The maximum range of the second scale.
		 * @return	The scaled value.
		 */
		public static function scale(value:Number, min:Number, max:Number, min2:Number, max2:Number):Number
		{
			return min2 + ((value - min) / (max - min)) * (max2 - min2);
		}
		
		/**
		 * Transfers a value from one scale to another scale, but clamps the return value within the second scale.
		 * @param	value		The value on the first scale.
		 * @param	min			The minimum range of the first scale.
		 * @param	max			The maximum range of the first scale.
		 * @param	min2		The minimum range of the second scale.
		 * @param	max2		The maximum range of the second scale.
		 * @return	The scaled and clamped value.
		 */
		public static function scaleClamp(value:Number, min:Number, max:Number, min2:Number, max2:Number):Number
		{
			value = min2 + ((value - min) / (max - min)) * (max2 - min2);
			if (max2 > min2)
			{
				value = value < max2 ? value : max2;
				return value > min2 ? value : min2;
			}
			value = value < min2 ? value : min2;
			return value > max2 ? value : max2;
		}
		
		/**
		 * The random seed used by FP's random functions.
		 */
		public static function get randomSeed():uint { return _getSeed; }
		public static function set randomSeed(value:uint):void
		{
			_seed = clamp(value, 1, 2147483646);
			_getSeed = _seed;
		}
		
		/**
		 * Randomizes the random seed using Flash's Math.random() function.
		 */
		public static function randomizeSeed():void
		{
			randomSeed = 2147483647 * Math.random();
		}
		
		/**
		 * A pseudo-random Number produced using FP's random seed, where 0 <= Number < 1.
		 */
		public static function get random():Number
		{
			_seed = (_seed * 16807) % 2147483647;
			return _seed / 2147483647;
		}
		
		/**
		 * Returns a pseudo-random uint.
		 * @param	amount		The returned uint will always be 0 <= uint < amount.
		 * @return	The uint.
		 */
		public static function rand(amount:uint):uint
		{
			_seed = (_seed * 16807) % 2147483647;
			return (_seed / 2147483647) * amount;
		}
		
		/**
		 * Returns the next item after current in the list of options.
		 * @param	current		The currently selected item (must be one of the options).
		 * @param	options		An array of all the items to cycle through.
		 * @param	loop		If true, will jump to the first item after the last item is reached.
		 * @return	The next item in the list.
		 */
		public static function next(current:*, options:Array, loop:Boolean = true):*
		{
			if (loop) return options[(options.indexOf(current) + 1) % options.length];
			return options[Math.max(options.indexOf(current) + 1, options.length - 1)];
		}
		
		/**
		 * Returns the item previous to the current in the list of options.
		 * @param	current		The currently selected item (must be one of the options).
		 * @param	options		An array of all the items to cycle through.
		 * @param	loop		If true, will jump to the last item after the first is reached.
		 * @return	The previous item in the list.
		 */
		public static function prev(current:*, options:Array, loop:Boolean = true):*
		{
			if (loop) return options[((options.indexOf(current) - 1) + options.length) % options.length];
			return options[Math.max(options.indexOf(current) - 1, 0)];
		}
		
		/**
		 * Swaps the current item between a and b. Useful for quick state/string/value swapping.
		 * @param	current		The currently selected item.
		 * @param	a			Item a.
		 * @param	b			Item b.
		 * @return	Returns a if current is b, and b if current is a.
		 */
		public static function swap(current:*, a:*, b:*):*
		{
			return current == a ? b : a;
		}
		
		/**
		 * Creates a color value by combining the chosen RGB values.
		 * @param	R		The red value of the color, from 0 to 255.
		 * @param	G		The green value of the color, from 0 to 255.
		 * @param	B		The blue value of the color, from 0 to 255.
		 * @return	The color uint.
		 */
		public static function getColorRGB(R:uint = 0, G:uint = 0, B:uint = 0):uint
		{
			return R << 16 | G << 8 | B;
		}
		
		/**
		 * Creates a color value with the chosen HSV values.
		 * @param	h		The hue of the color (from 0 to 1).
		 * @param	s		The saturation of the color (from 0 to 1).
		 * @param	v		The value of the color (from 0 to 1).
		 * @return	The color uint.
		 */
		public static function getColorHSV(h:Number, s:Number, v:Number):uint
		{
			h = h < 0 ? 0 : (h > 1 ? 1 : h);
			s = s < 0 ? 0 : (s > 1 ? 1 : s);
			v = v < 0 ? 0 : (v > 1 ? 1 : v);
			h = int(h * 360);
			var hi:int = int(h / 60) % 6,
				f:Number = h / 60 - int(h / 60),
				p:Number = (v * (1 - s)),
				q:Number = (v * (1 - f * s)),
				t:Number = (v * (1 - (1 - f) * s));
			switch (hi)
			{
				case 0: return int(v * 255) << 16 | int(t * 255) << 8 | int(p * 255);
				case 1: return int(q * 255) << 16 | int(v * 255) << 8 | int(p * 255);
				case 2: return int(p * 255) << 16 | int(v * 255) << 8 | int(t * 255);
				case 3: return int(p * 255) << 16 | int(q * 255) << 8 | int(v * 255);
				case 4: return int(t * 255) << 16 | int(p * 255) << 8 | int(v * 255);
				case 5: return int(v * 255) << 16 | int(p * 255) << 8 | int(q * 255);
				default: return 0;
			}
			return 0;
		}
		
		/**
		 * Finds the red factor of a color.
		 * @param	color		The color to evaluate.
		 * @return	A uint from 0 to 255.
		 */
		public static function getRed(color:uint):uint
		{
			return color >> 16 & 0xFF;
		}
		
		/**
		 * Finds the green factor of a color.
		 * @param	color		The color to evaluate.
		 * @return	A uint from 0 to 255.
		 */
		public static function getGreen(color:uint):uint
		{
			return color >> 8 & 0xFF;
		}
		
		/**
		 * Finds the blue factor of a color.
		 * @param	color		The color to evaluate.
		 * @return	A uint from 0 to 255.
		 */
		public static function getBlue(color:uint):uint
		{
			return color & 0xFF;
		}
		
		/**
		 * Fetches a stored BitmapData object represented by the source.
		 * @param	source		Embedded Bitmap class.
		 * @return	The stored BitmapData object.
		 */
		public static function getBitmap(source:Class):BitmapData
		{
			if (_bitmap[String(source)]) return _bitmap[String(source)];
			return (_bitmap[String(source)] = (new source).bitmapData);
		}
		
		/**
		 * Sets a time flag.
		 * @return	Time elapsed (in milliseconds) since the last time flag was set.
		 */
		public static function timeFlag():uint
		{
			var t:uint = getTimer(),
				e:uint = t - _time;
			_time = t;
			return e;
		}
		
		/**
		 * The global Console object.
		 */
		public static function get console():Console
		{
			if (!_console) _console = new Console;
			return _console;
		}
		
		/**
		 * Logs data to the console.
		 * @param	...data		The data parameters to log, can be variables, objects, etc. Parameters will be separated by a space (" ").
		 */
		public static function log(...data):void
		{
			if (_console)
			{
				if (data.length > 1)
				{
					var i:int = 0, s:String = "";
					while (i < data.length)
					{
						if (i > 0) s += " ";
						s += data[i ++].toString();
					}
					_console.log(s);
				}
				else _console.log(data[0]);
			}
		}
		
		/**
		 * Adds properties to watch in the console's debug panel.
		 * @param	...properties		The properties (strings) to watch.
		 */
		public static function watch(...properties):void
		{
			if (_console)
			{
				if (properties.length > 1) _console.watch(properties);
				else _console.watch(properties[0]);
			}
		}
		
		/**
		 * Loads the file as an XML object.
		 * @param	file		The embedded file to load.
		 * @return	An XML object representing the file.
		 */
		public static function getXML(file:Class):XML
		{
			var bytes:ByteArray = new file;
			return XML(bytes.readUTFBytes(bytes.length));
		}
		
		/**
		 * Tweens numeric public properties of an Object. Shorthand for creating a MultiVarTween tween, starting it and adding it to a Tweener.
		 * @param	object		The object containing the properties to tween.
		 * @param	values		An object containing key/value pairs of properties and target values.
		 * @param	duration	Duration of the tween.
		 * @param	options		An object containing key/value pairs of the following optional parameters:
		 * 						type		Tween type.
		 * 						complete	Optional completion callback function.
		 * 						ease		Optional easer function.
		 * 						tweener		The Tweener to add this Tween to.
		 * @return	The added MultiVarTween object.
		 * 
		 * Example: FP.tween(object, { x: 500, y: 350 }, 2.0, { ease: easeFunction, complete: onComplete } );
		 */
		public static function tween(object:Object, values:Object, duration:Number, options:Object = null):MultiVarTween
		{
			if (options && options.hasOwnProperty("delay")) {
				var delay:Number = options.delay;
				delete options.delay;
				FP.alarm(delay, function ():void { FP.tween(object, values, duration, options); });
				return null;
			}
			
			var type:uint = Tween.ONESHOT,
				complete:Function = null,
				ease:Function = null,
				tweener:Tweener = FP.tweener;
			if (object is Tweener) tweener = object as Tweener;
			if (options)
			{
				if (options is Function) complete = options as Function;
				if (options.hasOwnProperty("type")) type = options.type;
				if (options.hasOwnProperty("complete")) complete = options.complete;
				if (options.hasOwnProperty("ease")) ease = options.ease;
				if (options.hasOwnProperty("tweener")) tweener = options.tweener;
			}
			var tween:MultiVarTween = new MultiVarTween(complete, type);
			tween.tween(object, values, duration, ease);
			tweener.addTween(tween);
			return tween;
		}
		
		/**
		 * Schedules a callback for the future. Shorthand for creating an Alarm tween, starting it and adding it to a Tweener.
		 * @param	delay		The duration to wait before calling the callback.
		 * @param	callback	The function to be called.
		 * @param	type		The tween type (PERSIST, LOOPING or ONESHOT). Defaults to ONESHOT.
		 * @param	tweener		The Tweener object to add this Alarm to. Defaults to FP.tweener.
		 * @return	The added Alarm object.
		 * 
		 * Example: FP.alarm(5.0, callbackFunction, Tween.LOOPING); // Calls callbackFunction every 5 seconds
		 */
		public static function alarm(delay:Number, callback:Function, type:uint = 2, tweener:Tweener = null):Alarm
		{
			if (! tweener) tweener = FP.tweener;
			
			var alarm:Alarm = new Alarm(delay, callback, type);
			
			tweener.addTween(alarm, true);
			
			return alarm;
		}
		
		/**
		 * Gets an array of frame indices.
		 * @param	from	Starting frame.
		 * @param	to		Ending frame.
		 * @param	skip	Skip amount every frame (eg. use 1 for every 2nd frame).
		 */
		public static function frames(from:int, to:int, skip:int = 0):Array
		{
			var a:Array = [];
			skip ++;
			if (from < to)
			{
				while (from <= to)
				{
					a.push(from);
					from += skip;
				}
			}
			else
			{
				while (from >= to)
				{
					a.push(from);
					from -= skip;
				}
			}
			return a;
		}
		
		/**
		 * Shuffles the elements in the array.
		 * @param	a		The Object to shuffle (an Array or Vector).
		 */
		public static function shuffle(a:Object):void
		{
			if (a is Array || a is Vector.<*>)
			{
				var i:int = a.length, j:int, t:*;
				while (-- i)
				{
					t = a[i];
					a[i] = a[j = FP.rand(i + 1)];
					a[j] = t;
				}
			}
		}
		
		/**
		 * Sorts the elements in the array.
		 * @param	object		The Object to sort (an Array or Vector).
		 * @param	ascending	If it should be sorted ascending (true) or descending (false).
		 */
		public static function sort(object:Object, ascending:Boolean = true):void
		{
			if (object is Array || object is Vector.<*>) quicksort(object, 0, object.length - 1, ascending);
		}
		
		/**
		 * Sorts the elements in the array by a property of the element.
		 * @param	object		The Object to sort (an Array or Vector).
		 * @param	property	The numeric property of object's elements to sort by.
		 * @param	ascending	If it should be sorted ascending (true) or descending (false).
		 */
		public static function sortBy(object:Object, property:String, ascending:Boolean = true):void
		{
			if (object is Array || object is Vector.<*>) quicksortBy(object, 0, object.length - 1, ascending, property);
		}
		
		/** @private Quicksorts the array. */ 
		private static function quicksort(a:Object, left:int, right:int, ascending:Boolean):void
		{
			var i:int = left, j:int = right, t:Number,
				p:* = a[Math.round((left + right) * .5)];
			if (ascending)
			{
				while (i <= j)
				{
					while (a[i] < p) i ++;
					while (a[j] > p) j --;
					if (i <= j)
					{
						t = a[i];
						a[i ++] = a[j];
						a[j --] = t;
					}
				}
			}
			else
			{
				while (i <= j)
				{
					while (a[i] > p) i ++;
					while (a[j] < p) j --;
					if (i <= j)
					{
						t = a[i];
						a[i ++] = a[j];
						a[j --] = t;
					}
				}
			}
			if (left < j) quicksort(a, left, j, ascending);
			if (i < right) quicksort(a, i, right, ascending);
		}
		
		/** @private Quicksorts the array by the property. */ 
		private static function quicksortBy(a:Object, left:int, right:int, ascending:Boolean, property:String):void
		{
			var i:int = left, j:int = right, t:Object,
				p:* = a[Math.round((left + right) * .5)][property];
			if (ascending)
			{
				while (i <= j)
				{
					while (a[i][property] < p) i ++;
					while (a[j][property] > p) j --;
					if (i <= j)
					{
						t = a[i];
						a[i ++] = a[j];
						a[j --] = t;
					}
				}
			}
			else
			{
				while (i <= j)
				{
					while (a[i][property] > p) i ++;
					while (a[j][property] < p) j --;
					if (i <= j)
					{
						t = a[i];
						a[i ++] = a[j];
						a[j --] = t;
					}
				}
			}
			if (left < j) quicksortBy(a, left, j, ascending, property);
			if (i < right) quicksortBy(a, i, right, ascending, property);
		}
		
		// World information.
		/** @private */ internal static var _world:World;
		/** @private */ internal static var _goto:World;
		
		// Console information.
		/** @private */ internal static var _console:Console;
		
		// Time information.
		/** @private */ internal static var _time:uint;
		/** @private */ public static var _updateTime:uint;
		/** @private */ public static var _renderTime:uint;
		/** @private */ public static var _gameTime:uint;
		/** @private */ public static var _flashTime:uint;
		
		// Bitmap storage.
		/** @private */ private static var _bitmap:Object = { };
		
		// Pseudo-random number generation (the seed is set in Engine's contructor).
		/** @private */ private static var _seed:uint = 0;
		/** @private */ private static var _getSeed:uint;
		
		// Volume control.
		/** @private */ private static var _volume:Number = 1;
		/** @private */ private static var _pan:Number = 0;
		/** @private */ private static var _soundTransform:SoundTransform = new SoundTransform;
		
		// Used for rad-to-deg and deg-to-rad conversion.
		/** @private */ public static const DEG:Number = -180 / Math.PI;
		/** @private */ public static const RAD:Number = Math.PI / -180;
		
		// Global Flash objects.
		/** @private */ public static var stage:Stage;
		/** @private */ public static var engine:Engine;
		
		// Global objects used for rendering, collision, etc.
		/** @private */ public static var point:Point = new Point;
		/** @private */ public static var point2:Point = new Point;
		/** @private */ public static var zero:Point = new Point;
		/** @private */ public static var rect:Rectangle = new Rectangle;
		/** @private */ public static var matrix:Matrix = new Matrix;
		/** @private */ public static var sprite:Sprite = new Sprite;
		/** @private */ public static var entity:Entity;
	}
}