Трабл с програмным рисованием толстых линий

[opex]

Xb = 0;
Yb = 0;
p = 0;
this.createEmptyMovieClip("bg", 100);
with (this.bg) {
	beginFill(0xFFFFFF, 0);
	moveTo(0, 0);
	lineTo(Stage.width, 0);
	lineTo(Stage.width, Stage.height);
	lineTo(0, Stage.height);
	lineTo(0, 0);
	endFill;
}
this.bg.useHandCursor = 0;
this.bg.onRollOver = function() {
	p = 1;
};
this.bg.onRollOut = function() {
	p = 0;
};
lineStyle(15, 0x000000, 100);
function ris() {
	if (Key.isDown(1) && p == 1) {
		moveTo(Xb, Yb);
		lineTo(_root._xmouse, _root._ymouse);
		Xb = _root._xmouse;
		Yb = _root._ymouse;
	}
}
this.onMouseDown = function() {
	Xb = _root._xmouse;
	Yb = _root._ymouse;
};
setInterval(ris, 1);