A slow bug just reverses directions when it hits the edge of the window, whereas a fast bug tunnels through and reappears at the opposite side of the window.

• 慢臭虫仅仅在它碰到窗口边界时才掉转方向，然而快臭虫遇到这种情况时会直接穿过去，然后重新出现在窗口里相反的一边。