I played for about 30 min, and ended up with 187 defense on level 19 (not sure if there is a limit to the number of levels) and nothing could hurt me, but oddly only regular mice were spawning.
Once the game crashed (maybe an infinite loop) when going though a door. About 10% of levels were unsolvable, usually because there was no way to pull or push the block around a tight corner, or a treasure box was blocking, so thank you for the skip button.
Overall, very enjoyable concept that I'd like to see expanded.