private void loadPowerUpSprites() {
        // create "goal" sprite
        Animation anim = new Animation();
        anim.addFrame(loadImage("heart1.png"), 150);
        anim.addFrame(loadImage("heart2.png"), 150);
        anim.addFrame(loadImage("heart3.png"), 150);
        anim.addFrame(loadImage("heart2.png"), 150);
        goalSprite = new PowerUp.Goal(anim);

        // create "star" sprite
        anim = new Animation();
        anim.addFrame(loadImage("bottle.png"), 100);
        anim.addFrame(loadImage("bottle.png"), 100);
        coinSprite = new PowerUp.Star(anim);

        // create "music" sprite
        anim = new Animation();
        anim.addFrame(loadImage("music1.png"), 150);
        anim.addFrame(loadImage("music2.png"), 150);
        anim.addFrame(loadImage("music3.png"), 150);
        anim.addFrame(loadImage("music2.png"), 150);
        musicSprite = new PowerUp.Music(anim);
    }