Very interesting concept! The pixel-art is lovely, it makes the exploration enjoyable. Solving that puzzle felt a bit like solving a sudoku, locking more and more rooms until there's only a few left.
I think the game could enhance it's introduction or presentation though. At my first try, I didn't understood what the slot machines or the key were doing, or what was my goal. The start screen (the one presenting the goal) goes really fast. Actually maybe the word "Goal" could stay through the whole game? Globally maybe there could be more explanatory text in the game.
Also while I liked the exploration, none of the room felt recognizable. Thus I wasn't sure if they were changing or not, at the end it was just random room of platforming. I don't know what could be done to add some landmarks to the rooms, to feel like they belong to a larger space and are either shifting or familiar.
But that's a more "long term" issue. I still enjoyed discovering the game, and solving it. Plus, I love its minimalist approach, giving the less directions as possible and letting the player explore for themselves. Sure it's as the risk of letting the player a bit confused, but it's the kind of game-design I crave for. And overall despite some issues, this globally succeeds! :)