Thank you for the reply!
There was the blue bar at the bottom that appears at the start of interaction and decreases as you wait. I was worried it wouldn't be clear enough. If I ever continue developing that game I'll certainly try to make the rules easier to understand.
Originally wanted to also add interaction animation (like a key circling the lock or sth) to make it really obvious that things are happening. Maybe also have some intro level without enemies to give people enough time to understand how interactions work. But time ran out so none of that happened :(