Basic Filler engine with Box2D – part 1

package {
	import flash.display.Sprite;
	import flash.events.Event;
	import flash.events.MouseEvent;
 
	import Box2D.Dynamics.*;
	import Box2D.Collision.*;
	import Box2D.Collision.Shapes.*;
	import Box2D.Common.Math.*;
 
	public class colorballz extends Sprite {
		public var m_dbgSprite;
		public var m_world:b2World;
		public var m_phys_scale:Number = 30;
		public var m_timestep:Number = 1.0/30.0;
		public var m_iterations:Number = 10.0;
 
		//initial box coordinates when we first press mouse down
		public var initX:Number = 0.0;
		public var initY:Number = 0.0;
		public var drawing:Boolean = false;
		public var b:b2Body;
 
		//
		public var the_ball:ball;
		public function colorballz() {
			/*
			A Box2D world needs three parameters: a b2AABB, gravity
			and a Booleand deciding whether or not to let bodies sleep
			when they are not being simulated.
			This saves CPU so should always be left on :)
			*/
 
			var gravity:b2Vec2 = new b2Vec2(0,9.8);
			var worldAABB:b2AABB = new b2AABB();
			worldAABB.lowerBound.Set(-1000,-1000);
			worldAABB.upperBound.Set(1000,1000);
			m_world = new b2World(worldAABB,gravity,true);
 
			//Add Our Ground
			AddStaticBox(250/m_phys_scale,510/m_phys_scale,250/m_phys_scale,10/m_phys_scale);
			AddStaticBox(250/m_phys_scale,-10/m_phys_scale,250/m_phys_scale,10/m_phys_scale);
			AddStaticBox(-10/m_phys_scale,250/m_phys_scale,10/m_phys_scale,250/m_phys_scale);
			AddStaticBox(510/m_phys_scale,250/m_phys_scale,10/m_phys_scale,250/m_phys_scale);
 
			addEventListener(Event.ENTER_FRAME,Update);
			stage.addEventListener(MouseEvent.MOUSE_DOWN,mousePressed);
			stage.addEventListener(MouseEvent.MOUSE_MOVE,mouseMoved);
			stage.addEventListener(MouseEvent.MOUSE_UP,mouseReleased);
		}
		public function mousePressed(e:MouseEvent) {
			//Store initial X and Y position
			initX = e.localX;
			initY = e.localY;
			the_ball = new ball();
			the_ball.x = mouseX;
			the_ball.y = mouseY;
			the_ball.width = 1;
			the_ball.height = 1;
			addChild(the_ball);
			drawing = true;
		}
		public function mouseMoved(e:MouseEvent) {
			if (drawing) {
				the_ball.x = mouseX;
				the_ball.y = mouseY;
			}
		}
		public function mouseReleased(e:MouseEvent) {
			drawing = false;
			addCircle( mouseX,  mouseY, the_ball.width/2,the_ball);
		}
		public function addCircle(_x:Number, _y:Number, _radius:Number,ballclip:ball) {
			var bd:b2BodyDef = new b2BodyDef();
			var cd:b2CircleDef = new b2CircleDef();
			var area:Number = Math.floor(_radius*_radius*Math.PI/25)/100;
			// area is the % of the entire stage filled by the circle
			// the entire stage area is 500*500 = 250000 pixels
			// circle area is radius*radius*PI
			// so the % is radius*radius*PI*100/250000
			cd.radius = Math.abs(_radius)/m_phys_scale;
			cd.density = 2;
			cd.restitution = 0.7;
			cd.friction = 2;
			bd.position.Set(_x/m_phys_scale, _y/ m_phys_scale);
			bd.userData = ballclip;
			b = m_world.CreateBody(bd);
			b.CreateShape(cd);
			b.SetMassFromShapes();
		}
		public function AddStaticBox(_x:Number,_y:Number,_halfwidth:Number,_halfheight:Number) {
			var bodyDef:b2BodyDef = new b2BodyDef();
			bodyDef.position.Set(_x,_y);
			var boxDef:b2PolygonDef = new b2PolygonDef();
			boxDef.SetAsBox(_halfwidth,_halfheight);
			boxDef.density = 0.0;
			var body:b2Body = m_world.CreateBody(bodyDef);
			body.CreateShape(boxDef);
			body.SetMassFromShapes();
		}
		public function Update(e:Event) {
			//We need to do this to simulate physics
			if (drawing) {
				the_ball.width+=2;
				the_ball.height+= 2;
			}
			m_world.Step(m_timestep,m_iterations);
			for (var bb:b2Body=m_world.m_bodyList; bb; bb=bb.m_next) {
				if (bb.m_userData is Sprite) {
					bb.m_userData.x=bb.GetPosition().x * 30;
					bb.m_userData.y=bb.GetPosition().y * 30;
					bb.m_userData.rotation=bb.GetAngle() * 180 / Math.PI;
				}
			}
		}
	}
}