Free ActionScript

/**
 * Car Movement - Accelerate, Brake & Rotate
 * ---------------------
 * VERSION: 1.0
 * DATE: 6/22/2010
 * AS3
 * UPDATES AND DOCUMENTATION AT: http://www.FreeActionScript.com
 **/
package com.freeactionscript 
{
	import flash.display.MovieClip;
	import flash.display.Sprite;
	import flash.events.Event;
	import flash.events.MouseEvent;
	import flash.events.Event;
	import flash.events.KeyboardEvent;
	import flash.ui.Keyboard;
 
	public class Car extends Sprite
	{
		//Settings
		private var speed:Number = 0;
		private var speedMax:Number = 4;
		private var speedMaxReverse:Number = -1;
		private var speedAcceleration:Number = .15;
		private var speedDeceleration:Number = .90;
		private var groundFriction:Number = .95;
 
		private var steering:Number = 0;
		private var steeringMax:Number = 1;
		private var steeringAcceleration:Number = .10;
		private var steeringFriction:Number = .98;
 
		private var velocityX:Number = 0;
		private var velocityY:Number = 0;
		private var radiance:Number = 180 / Math.PI;
 
		private var up:Boolean = false;
		private var down:Boolean = false;
		private var left:Boolean = false;
		private var right:Boolean = false;
 
		public function Car()
		{
			addEventListener(Event.ADDED_TO_STAGE, onAddedToStage);
		}
 
		private function onAddedToStage(event:Event):void 
		{
			removeEventListener(Event.ADDED_TO_STAGE, onAddedToStage);
 
			init();
		}
 
		private function init():void
		{
			stage.addEventListener(Event.ENTER_FRAME, runGame);			
			stage.addEventListener(KeyboardEvent.KEY_DOWN, myOnPress);
			stage.addEventListener(KeyboardEvent.KEY_UP, myOnRelease);
		}
 
		private function runGame(event:Event):void
		{
			if (up)
			{
				//check if below speedMax
				if (speed < speedMax)
				{
					//speed up
					speed += speedAcceleration;
					//check if above speedMax
					if (speed > speedMax)
					{
						//reset to speedMax
						speed = speedMax;
					}
				}
			}
 
			if (down)
			{
				//check if below speedMaxReverse
				if (speed > speedMaxReverse)
				{
					//speed up (in reverse)
					speed -= speedAcceleration;
					//check if above speedMaxReverse
					if (speed < speedMaxReverse)
					{
						//reset to speedMaxReverse
						speed = speedMaxReverse;
					}
				}
			}
 
			if (left)
			{
				//turn left
				steering -= steeringAcceleration;
				//check if above steeringMax
				if (steering > steeringMax)
				{
					//reset to steeringMax
					steering = steeringMax;
				}
			}
 
			if (right)
			{
				//turn right
				steering += steeringAcceleration;
				//check if above steeringMax
				if (steering < -steeringMax)
				{
					//reset to steeringMax
					steering = -steeringMax;
				}
			}
 
			// friction    
			speed *= groundFriction;
 
			// prevents drift
			if (speed < 0.01)
			{
				speed = 0;
			}
 
			// ideal changes
			var idealXMovement = speed * Math.cos(radiance);
			var idealYMovement = speed * Math.sin(radiance);
 
			// real change
			velocityX += (idealXMovement - velocityX) * groundFriction;
			velocityY += (idealYMovement - velocityY) * groundFriction;
 
			// update position
			this.x += velocityX;
			this.y += velocityY;
 
			// rotate
			radiance += (steering * speed) * .025;
			this.rotation = radiance * 180 / Math.PI;
 
			// Fix Steering (make car go straight after driver stops turning)
			steering -= (steering * 0.1);
 
		}
 
		/**
		 * Keyboard Handlers
		 */
		private function myOnPress(event:KeyboardEvent):void
		{
			switch( event.keyCode )
			{
				case Keyboard.UP:
					up = true;
					break;
 
				case Keyboard.DOWN:
					down = true;
					break;
 
				case Keyboard.LEFT:
					left = true;
					break;
 
				case Keyboard.RIGHT:
					right = true;
					break;
			}
 
			event.updateAfterEvent();
		}
 
		private function myOnRelease(event:KeyboardEvent):void
		{
			switch( event.keyCode )
			{
				case Keyboard.UP:
					up = false;
					break;
 
				case Keyboard.DOWN:
					down = false;
					break;
 
				case Keyboard.LEFT:
					left = false;
					break;
 
				case Keyboard.RIGHT:
					right = false;
					break;
			}
 
		}
 
	}
 
}