/* GLOBAL VARIABLES */
_global.gLEFT = 20;
_global.gTOP = 20;
_global.gRIGHT = Stage.width - 20;
_global.gBOTTOM = Stage.height - 20;

/* FUNCTION: Converts radians to degrees */
function rad2deg(radians:Number):Number {
  return radians * 180 / Math.PI;
} 
 
/* FUNCTION: Converts degrees to radians */
function deg2rad(degrees:Number):Number {
  return degrees * Math.PI / 180;
}

/* FUNCTION: Returns a random number between min and max (inclusive) */
function randRange(min:Number, max:Number):Number {
  var randomNum:Number = Math.floor(Math.random() * (max - min + 1)) + min;
  return randomNum;
}

/* FUNCTION: Creates an explosion */
explosion.maxSpeed = 25;
explosion.minSize = 4;
explosion.maxSize = 10;
explosion.minFragments = 10;
explosion.maxFragments = 50;
function explosion(originX:Number, originY:Number):Void {
  var totalFragments:Number = randRange(explosion.minFragments, explosion.maxFragments);
  var fragment_mc:MovieClip;
  var depth:Number = this.getNextHighestDepth();
  for (var i:Number = 0; i < totalFragments; i++, depth++) {
    fragment_mc = attachMovie("Fragment", "fragment" + depth, depth);
    fragment_mc._x = originX;
    fragment_mc._y = originY;
    fragment_mc._width = fragment_mc._height = randRange(explosion.minSize, explosion.maxSize);
    while (!fragment_mc.speedX) {
      fragment_mc.speedX = randRange(-explosion.maxSpeed, explosion.maxSpeed);
    }
    while (!fragment_mc.speedY) {
      fragment_mc.speedY = randRange(-explosion.maxSpeed, explosion.maxSpeed);
    }
    fragment_mc._alpha = randRange(10, 100);
    fragment_mc.cacheAsBitmap = true;
 
    fragment_mc.onEnterFrame = function():Void {
      this._x += this.speedX;
      this._y += this.speedY;
 
      if (this._x < gLEFT || this._x > gRIGHT || this._y < gTOP || this._y > gBOTTOM) {
        this.removeMovieClip();
      }
    };
  }
}

/* FUNCTION: Creates and initializes heat-seeking missiles */
createMissile.maxSpeed = 30;
createMissile.accel = 2;
function createMissile(target_mc:MovieClip, xPos:Number, yPos:Number):Void {
  var depth:Number = _root.getNextHighestDepth();
  var missile_mc:MovieClip = attachMovie("Missile", "missile" + depth, depth);
  missile_mc._x = xPos;
  missile_mc._y = yPos;
  missile_mc.speed = 0;
 
  missile_mc.setRotation = function():Void {
    var dy:Number = target_mc._y - this._y;
    var dx:Number = target_mc._x - this._x;
    this._rotation = rad2deg(Math.atan2(dy, dx));
  };
 
  missile_mc.onEnterFrame = function():Void {
    this.setRotation();
 
    if (this.speed < createMissile.maxSpeed) {
      this.speed += createMissile.accel;
    }
    this._x += Math.cos(deg2rad(this._rotation)) * this.speed;
    this._y += Math.sin(deg2rad(this._rotation)) * this.speed;
 
    if (this.hitTest(target_mc)) {
      explosion(target_mc._x, target_mc._y);
      this.removeMovieClip();
    }
  };
}

/* MAIN PROGRAM LOGIC */
var gameBG_mc:MovieClip = _root.createEmptyMovieClip("gameBG", 0);
gameBG_mc.beginFill(0x222222);
gameBG_mc.moveTo(gLEFT, gTOP);
gameBG_mc.lineTo(gRIGHT, gTOP);
gameBG_mc.lineTo(gRIGHT, gBOTTOM);
gameBG_mc.lineTo(gLEFT, gBOTTOM);
gameBG_mc.endFill(gLEFT, gTOP);
 
var target_mc:MovieClip = attachMovie("Target", "target", _root.getNextHighestDepth());
var startX:Number = (gRIGHT - gLEFT) / 2 + gLEFT;
var startY:Number = (gBOTTOM - gTOP) / 2 + gTOP;
startDrag(target_mc, true);
Mouse.hide();
 
onMouseDown = function():Void {
  createMissile(target_mc, startX, startY);
};