Thanks a lot for playing and for the feedback. Glad you enjoyed the challeng.
The doors actually have three states: closed, peeking, and open. The peeking state is a little stealth mechanic so you can look behind a door without being spotted from the other side. Some doors are also lever-controlled, meaning they only open/close with a lever, but you can still peek behind them.
About the levels: we split Level 3 & 4 pretty late in the jam, so they both ended up on the same map. Each time, a different building gets unlocked. Totally get how that was confusing when you entered Level 3 and saw "Level 4" written on one of the buildings 😅