// no parent?  then go free!
				this.velocity.y++;
				this.position.x += this.velocity.x;
				this.position.y += this.velocity.y;
			}else{
				// trail behind our parent shape
				px = this.parentShape.position.x;
				py = this.parentShape.position.y;
				oldx = this.position.x;
				oldy = this.position.y;
				dx = px - oldx;
				dy = py - oldy;
				dist = Math.sqrt(dx * dx + dy * dy);
				dy *= linkSize / dist;
				dx *= linkSize / dist;
				this.position = {
					'x' : px - dx,
					'y' : py - dy
				}