translation.en: Any time you go backwards, any time you skip a step -- imagine walking up a staircase where some of the treads are missing, or the heights are different.
translation.zh: 任何时候你后退，或者是跳过什么步骤-- 就像你走到一个楼梯，发现有些台阶不见了， 或者是台阶的高度不一样。