[讨论]飞机游戏中的跟踪子弹

//- ATTACH AIM INTO THE CONTAINER -//
var scene:MovieClip = this.createEmptyMovieClip ("scene", 1);
scene.depth = 1;
var objectsInScene:Array = new Array ();
function addEnemy ()
{
for (var i = 0; i < 5; i++)
{
var aim:MovieClip = scene.attachMovie ("aim", "aim" + i, scene.depth++);
aim._x = random (500);
aim._y = random (400);
aim.exist = true;
objectsInScene.push (aim);
}
}
setInterval (addEnemy, 2500);
//- ATTACH BULLET -//
onMouseDown = function ()
{
var b:MovieClip = scene.attachMovie ("bullet", "bullet" + scene.depth, scene.depth++);
b._x = _root._xmouse;
b._y = _root._ymouse;
b.radian = 0;
b.dir = (random (2) ? 1 : -1);
b.oldy = b._y;
b.oldx = b._x;
b.aim = objectsInScene[random(objectsInScene.length)];
b.onEnterFrame = shoot;
};
//- BULLET SHOOT -//
function shoot ()
{
if(this._x > 500) this.removeMovieClip();
else if(this._x < 0) this.removeMovieClip();
if(this._y > 400) this.removeMovieClip();
else if(this._y < 0) this.removeMovieClip();

var x, y;
var oa = objectsInScene;
if (!this.aim.exist)
{
if(oa.length)
this.aim = oa[random(oa.length)];
if (this.radian < 2)
{
this.radian += 0.1;
}

x = Math.cos (this.radian) * 15 * this.dir;
y = -Math.sin (this.radian) * 15;
}
else
{
var i = oa.length;
while(--i > -1)
{
if(this.hitTest(oa[i]))
{
oa[i].removeMovieClip();
oa.splice(i, 1);
this.removeMovieClip();
}
}
var r = Math.atan2 (this.aim._y - this._y, this.aim._x - this._x);
x = Math.cos (r) * 15;
y = Math.sin (r) * 15;
}
this._x += x;
this._y += y;
this._rotation = Math.atan2 (this._y - this.oldy, this._x - this.oldx) * 57.3;
this.oldy = this._y;
this.oldx = this._x;
}