Way of an Idea Box2D prototype – Step 2

package {
	import flash.display.Sprite;
	import flash.events.Event;
	import flash.events.MouseEvent;
	import flash.events.KeyboardEvent;
	import Box2D.Dynamics.*;
	import Box2D.Collision.*;
	import Box2D.Collision.Shapes.*;
	import Box2D.Common.Math.*;
	public class draw extends Sprite {
		public var drawing:Boolean=false;
		public var canvas:Sprite = new Sprite();
		public var points_array:Array;
		public var pixel_dist:int=20;
		public var saved_x:int;
		public var saved_y:int;
		public var m_world:b2World;
		public var body:b2Body;
		public var bodyDef:b2BodyDef = new b2BodyDef();
		public var circleDef:b2CircleDef= new b2CircleDef();
		// radians to degrees conversion
		public var rad_to_deg:Number=57.2957795;
		// simulation timestep. We start at zero.
		public var timestep:Number=0;
		public function draw():void {
			// world creation
			var worldAABB:b2AABB = new b2AABB();
			worldAABB.lowerBound.Set(-100.0, -100.0);
			worldAABB.upperBound.Set(100.0, 100.0);
			m_world=new b2World(worldAABB,new b2Vec2(0,10),true);
			//
			// *** IMPORTANT: NOTICE THERE ISN'T ANY DEBUG DRAW ROUTINE ***
			// 
			// placing the ball
			bodyDef.position.Set(20/30,20/30);
			circleDef.radius=15/30;
			circleDef.density=1;
			circleDef.friction=0.5;
			circleDef.restitution=0.2;
			// ball's movieclip attachment
			bodyDef.userData = new sphere();
			bodyDef.userData.x=20;
			bodyDef.userData.y=20;
			bodyDef.userData.width=30;
			bodyDef.userData.height=30;
			addChild(bodyDef.userData);
			// end ball's movieclip attachment
			body=m_world.CreateBody(bodyDef);
			body.CreateShape(circleDef);
			body.SetMassFromShapes();
			//
			addChild(canvas);
			canvas.graphics.lineStyle(5);
			stage.addEventListener(MouseEvent.MOUSE_DOWN,mouse_pressed);
			stage.addEventListener(MouseEvent.MOUSE_MOVE,mouse_moved);
			stage.addEventListener(MouseEvent.MOUSE_UP,mouse_released);
			addEventListener(Event.ENTER_FRAME, Update, false, 0, true);
			stage.addEventListener(KeyboardEvent.KEY_DOWN, key_down);
 
		}
		public function mouse_pressed(e:MouseEvent):void {
			drawing=true;
			canvas.graphics.moveTo(mouseX,mouseY);
			points_array=new Array();
			saved_x=mouseX;
			saved_y=mouseY;
			points_array.push(saved_x);
			points_array.push(saved_y);
		}
		public function mouse_moved(e:MouseEvent):void {
			if (drawing) {
				var dist_x:int=mouseX-saved_x;
				var dist_y:int=mouseY-saved_y;
				if (dist_x*dist_x+dist_y*dist_y>pixel_dist*pixel_dist) {
					canvas.graphics.lineTo(mouseX,mouseY);
					saved_x=mouseX;
					saved_y=mouseY;
					points_array.push(saved_x);
					points_array.push(saved_y);
				}
			}
		}
		public function mouse_released(e:MouseEvent):void {
			drawing=false;
			var sx:int;
			var ex:int;
			var sy:int;
			var ey:int;
			var dist_x:int;
			var dist_y:int;
			var dist:Number;
			var angle:Number;
			var segments:int=points_array.length/2-1;
			for (var i:int=0; i<segments; i++) {
				sx=points_array[i*2];
				sy=points_array[i*2+1];
				ex=points_array[i*2+2];
				ey=points_array[i*2+3];
				dist_x=sx-ex;
				dist_y=sy-ey;
				dist=Math.sqrt(dist_x*dist_x+dist_y*dist_y);
				angle=Math.atan2(dist_y,dist_x);
				create_box((sx+ex)/60,(sy+ey)/60,Math.abs(dist)/60,2/30,angle);
			}
			canvas.graphics.clear();
			canvas.graphics.lineStyle(5);
		}
		// function to be called if the player presses space
		// switching timestep
		public function key_down(event:KeyboardEvent):void {
			if (event.keyCode==32) {
				if (timestep) {
					timestep=0;
				} else {
					timestep=1/30;
				}
			}
		}
		public function create_box(px,py,w,h,a):void {
			var body:b2Body;
			var bodyDef:b2BodyDef;
			var boxDef:b2PolygonDef;
			bodyDef = new b2BodyDef();
			bodyDef.position.Set(px,py);
			bodyDef.angle=a;
			boxDef = new b2PolygonDef();
			boxDef.SetAsBox(w,h);
			boxDef.friction=0.3;
			boxDef.density=0;
			// box's movieclip attachment
			bodyDef.userData = new chalk();
			bodyDef.userData.x=px*30;
			bodyDef.userData.y=py*30;
			bodyDef.userData.width=w*60;
			bodyDef.userData.height=h*60;
			bodyDef.userData.rotation=a*rad_to_deg;
			addChild(bodyDef.userData);
			// end box's movieclip attachment
			body=m_world.CreateBody(bodyDef);
			body.CreateShape(boxDef);
			body.SetMassFromShapes();
		}
		public function Update(e:Event):void {
			// executing Step function and updating movieclips positions only 
			// if timestep != 0
			if (timestep) {
				m_world.Step(timestep, 10);
				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);
					}
				}
			}
		}
	}
}