I really really love the concept of this game. It's super fun and the player really gets immersed in the game. If you were to continue to update and enhance the game further, one thing I would recommend is definitely polishing the player movement speeds, jumps, etc, as it felt very fast paced (I know this may be your intention as you are playing as a rat) but maybe almost too fast? It would be cool if you are able to make the rat climb on walls too. I would also lower the jump height of the player too.
I really love the environment that you have created though, the lighting adds to it a lot.