public void update() {
		for (int i = 0; i < bullets.size(); i++) {
			Bullet bullet = bullets.get(i);
			bullet.fly();

			for (int j = 0; j < enemies.size(); j++) {
				Enemy enemy = enemies.get(j);

				if (GameTool.isCollision(bullet, enemy)) {
					// 敵人要消失
					enemies.remove(enemy);

					// 子彈要消失
					bullets.remove(bullet);
				}
			}
		}

		for (int i = 0; i < eBullets.size(); i++) {
			EnemyBullet eb = eBullets.get(i);
			eb.fly();

			if (GameTool.isCollision(eb, player)) {
				// 自己要消失
				player = null;

				// 子彈要消失
				eBullets.remove(eb);
			}
		}
	}