A safe direction means a direction in which a bullet cannot possibly strike anyone, taking into account possible ricochets and the fact that bullets can penetrate walls and ceilings. “安全的方向”指在这个方向上弹头不会击中任何人,在确定这一点时要考虑到跳弹、考虑到弹头可能穿透墙壁和天花板。
In squash, you have to learn to play the ricochets. 在壁球中,你必须学习打反弹球。