protected void animate(
	final Sprite sprite,
	final SpriteRender spriteRender,
	final int ballSize, final int ballIndex, final int batchSize, final int delta
) {
	final float ballRadius = ballSize * 0.5f;
	final float boundW = SCREEN_WIDTH - ballRadius;
	final float boundH = SCREEN_HEIGHT - ballRadius;

	final Sprite[] sprites = sprite.asArray();
	final SpriteRender[] spritesRender = spriteRender.asArray();
	for ( int b = ballIndex, r = 0, len = (ballIndex + batchSize); b < len; b++, r++ ) {
		float x = sprites[b].x;
		float dx = sprites[b].dx;

		x += dx * delta;
		if ( x < ballRadius ) {
			x = ballRadius;
			sprites[b].dx = -dx;
		} else if ( x > boundW ) {
			x = boundW;
			sprites[b].dx = -dx;
		}
		sprites[b].x = x;

		float y = sprites[b].y;
		float dy = sprites[b].dy;

		y += dy * delta;
		if ( y < ballRadius ) {
			y = ballRadius;
			sprites[b].dy = -dy;
		} else if ( y > boundH ) {
			y = boundH;
			sprites[b].dy = -dy;
		}
		sprites[b].y = y;

		spritesRender[r].x = x;
		spritesRender[r].y = y;
	}

}