Comment by notpushkin

And a weird tangent on deterministic, idempotent elevator buttons [1]:

> I always get a bit nervous when someone tells me that in their country, you can press the elevator button again to unset it.

The way I’ve seen this solved in a lot of countries across SEA is that you unset the elevator button by double-pressing it. It’s not intuitive, and I’ve only discovered it by accident, but it’s deterministic and idempotent: one gesture sets the button, the other unsets it.

[1]: https://unsung.aresluna.org/deterministic-vs-idempotent/