When you've looked at a problem the same way for too long, every idea starts to look like the last one. Reversal shakes that loose. You write the problem as a sentence and turn it around: flip the goal, the direction, the order, the roles or the point of view. Then you ask what the upside-down version shows you.
Most reversed statements sound silly at first. “Instead of the app reminding users, users remind the app” isn't a plan. But it points somewhere new, and when you bring it back to reality it often becomes a practical idea you'd never have reached by pushing forward.
It's quick, it needs no training, and it works on almost anything: a goal, a process, a product or a rule.
Use it when your ideas all sound alike, when a team keeps pushing harder on the same approach, or when you want a quick, playful way to reframe a problem before an idea session.