Very challenging. Only about 30 sum doors in and I love it. You have to have knowledge to get through some doors and not just what’s around you in the room. Some levels I find difficult to understand though. I came across one and even after watching the walkthrough I didn’t understand how the answer worked, even looking in the comments others didn’t understand and I didn’t even understand when they were answered. And one of the beginning levels, I thought my hand would fall off and I’d never get through the door. I’m sure it will get even more difficult as I move through stages but I’m really enjoying it. I’m a sucker for escape games.