The game's really fun! I do have my complaints though. Your mouse stays locked in the center even if you exit the window, and that can be quite annoying. It's also a bummer you can't move with WASD, that makes playing in first person extremely uncomfortable.
It's an awesome looking base for a tileset, but I personally think it needs a bit more in it. The lack of decor apart from rocks means that a typical level designer would likely need to mix in elements from another tileset to keep their level looking interesting, and would struggle as a result.
So if you ever decide to work on a future update to this, I'd definitely advise adding a few more background elements here. Maybe a few semi solid platforms like in Mario Maker, some trees, some Halloween esque things like pumpkins, etc.