Really solid core mechanic that is expanded on with clever level design / puzzles. I had fun figuring out the right order to do things, and liked that the four guys weren't entirely interchangeable (e.g. for a timed switch, only the guy directly after the one pressing it can be the one going past the door).
I initially thought that skipping to the next character saved the time, but I figured out later that it didn't. That might be something that can be indicated more clearly via the things that happen when you press the button (e.g. maybe the time speeds up rather than just instantly skipping?). But it could also just me being a bit dense, ha