Basic Filler engine with Box2D – part 2

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;
		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 var the_enemy:enemy;
		public function colorballz() {
			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);
			//Add enemies
			for(var x:int=1;x<=3;x++){
				// the first parameter is enemy's radius
				addEnemy(10);
			}
			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) {
			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;
			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 addEnemy(_radius:Number) {
			var x_speed:Number = Math.random()*10;
			var bd:b2BodyDef = new b2BodyDef();
			var cd:b2CircleDef = new b2CircleDef();
			the_enemy = new(enemy);
			cd.radius=Math.abs(_radius)/m_phys_scale;
			cd.density=20;
			// setting restitution to 1 should grant the enemy won't lose speed when bouncing
			// on STATIC objects
			cd.restitution=1;
			cd.friction=2;
			// randomly placing the enemy
			bd.position.Set((Math.random()*300+50)/m_phys_scale, (Math.random()*300+50)/ m_phys_scale);
			bd.userData=the_enemy;
			bd.userData.name="enemy";
			bd.userData.width=_radius*2;
			bd.userData.height=_radius*2;
			addChild(the_enemy);
			b=m_world.CreateBody(bd);
			b.CreateShape(cd);
			b.SetMassFromShapes();
			// assigning random speed to enemy
			b.m_linearVelocity.x=x_speed;
			b.m_linearVelocity.y=10-x_speed;
		}
		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) {
			// variable to handle enemy speed
			var enemy_speed:Number;
			// variable to handle the speed offset:it's the ratio between
			// the real enemy speed and the minimum allowed speed
			var speed_offset:Number;
			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) {
					if (bb.m_userData.name=="enemy") {
						// determining enemy speed
						enemy_speed=Math.abs(bb.GetLinearVelocity().x)+Math.abs(bb.GetLinearVelocity().y);
						// if the speed is too slow... (lower than 10)
						if (enemy_speed<10) {
							// calculating the offset
							speed_offset=10/enemy_speed;
							// multiplying the horizontal and vertical components of the speed
							// by the offset
							bb.m_linearVelocity.x=bb.GetLinearVelocity().x*speed_offset;
							bb.m_linearVelocity.y=bb.GetLinearVelocity().y*speed_offset;
						}
					}
					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;
				}
			}
		}
	}
}