Thanks for the feedback, I'm glad you liked it!
Difficulty balance is the part I fear the most, for good reasons. I think it's easy too, but from the dev point of view is always tricky to tweak that, but I have some plans on how to do that. There were only two "floors" of the game in this demo, the idea is to increase number and type of enemies when advancing. Hopefully I will do that well :D
For the environment yeah, it's very bare-bones now. I'm thinking of adding a lot more detail, for graphical flavor, but also refine the room layouts and add some obstacles!
Thanks again for playing it!