But, you know, in 2D, the options are not just left and right or north and south, but infinity of possible directions in which I could go those 5 km.

但在二维空间中,不仅可以向左向右或者向南向北,我在走那5公里的时候可以有无数个方向

耶鲁公开课 - 基础物理课程节选