Emanuele Feronato

Create a Flash Racing Game Tutorial – AS3 version

Talking about Racing game, Actionscript 3, Flash and Game development.

The porting of the most popular AS2 tutorials continues with a basic AS3 version of the Flash racing game script.

I said “basic” because it does not have all features, this time it covers only movement and collision detection because I want to add more features before polishing it.

In the detail, I am developing an artificial intelligence algorithm to include cars controlled by the computer.

Meanwhile, this is the main class

package {
	import flash.display.Sprite;
	public class racing extends Sprite {
		public var car:car_mc;
		public var ground:ground_mc = new ground_mc();
		public function racing():void {
			car = new car_mc(450,300);
			addChild(ground);
			addChild(car);
		}
	}
}

And this is car_mc class:

package {
	import flash.display.Sprite;
	import flash.events.Event;
	import flash.events.KeyboardEvent;
	import flash.geom.Point;
	public class car_mc extends Sprite {
		public var acceleration:Number=0.4;
		public var speed_decay:Number=0.96;
		public var rotation_step:Number=10;
		public var max_speed:Number=10;
		public var back_speed:Number=1;
		public var speed:Number=0;
		public var accelerate,brake,turn_left,turn_right:Boolean=false;
		public function car_mc(posx:int,posy:int):void {
			x=posx;
			y=posy;
			addEventListener(Event.ADDED_TO_STAGE,init);
		}
		public function init(e:Event):void {
			addEventListener(Event.ENTER_FRAME,on_enter_frame);
			stage.addEventListener(KeyboardEvent.KEY_DOWN,on_key_down);
			stage.addEventListener(KeyboardEvent.KEY_UP,on_key_up);
		}
		public function on_enter_frame(e:Event):void {
			if (accelerate&&speed-1) {
				speed-=back_speed;
			}
			var speed_x:Number=Math.sin(rotation*0.0174532925)*speed;
			var speed_y:Number=- Math.cos(rotation*0.0174532925)*speed;
			if (turn_left) {
				rotation -= rotation_step*(speed/max_speed);
			}
			if (turn_right) {
				rotation += rotation_step*(speed/max_speed);
			}
			y+=speed_y;
			x+=speed_x;
			var point_left:Point=new Point(-9,0);
			var point_right:Point=new Point(9,0);
			var point_front:Point=new Point(0,-13);
			var point_back:Point=new Point(0,13);
			point_left=localToGlobal(point_left);
			point_right=localToGlobal(point_right);
			point_front=localToGlobal(point_front);
			point_back=localToGlobal(point_back);
			var par:racing=this.parent as racing;
			if (par.ground.hitTestPoint(point_left.x,point_left.y,true)) {
				rotation+=5;
				speed*=0.85;
			}
			if (par.ground.hitTestPoint(point_right.x,point_right.y,true)) {
				rotation-=5;
				speed*=0.85;
			}
			if (par.ground.hitTestPoint(point_front.x,point_front.y,true)) {
				speed*=0.55;
			}
			if (par.ground.hitTestPoint(point_back.x,point_back.y,true)) {
				speed*=0.55;
			}
			if (Math.abs(speed)>0.3) {
				speed*=speed_decay;
			} else {
				speed=0;
			}
		}
		public function on_key_down(e:KeyboardEvent):void {
			if (e.keyCode==38) {
				accelerate=true;
			}
			if (e.keyCode==40) {
				brake=true;
			}
			if (e.keyCode==37) {
				turn_left=true;
			}
			if (e.keyCode==39) {
				turn_right=true;
			}
		}
		public function on_key_up(e:KeyboardEvent):void {
			if (e.keyCode==38) {
				accelerate=false;
			}
			if (e.keyCode==40) {
				brake=false;
			}
			if (e.keyCode==37) {
				turn_left=false;
			}
			if (e.keyCode==39) {
				turn_right=false;
			}
		}
	}
}

And this is the result

Download the source code.