弓箭抛物线效果，精确定位到任何一点，弓箭自动带翻转效果。-Bows parabolic effect, precise positioning to any point, bows and arrows with rollover effect automatically.

子弹的代码实现,对于抛物线的算法，实现子弹的轨迹-Bullet code for parabolic algorithm, the trajectory of the bullet