Shame it was slightly late, but adding a few more weapons would have been helpful. I'll try to be a bit in-depth with this:
* The knife is a bit too weak, largely because of its range. Personally, I would have replaced it with a sword, giving it a reason for having more range. That said, I do feel it was offset by the fact you healed to full health after each room.
* If this is a casino, then you could make it more cluttered with, say, slot machines. You could even make it maze-like, reflective of how actual casinos are designed. The more cramped it is, the more I think weapons like the knife will thrive.
* I was a bit surprised when the rocket launcher didn't do self-damage. If you decide to combine that with the cramped gimmick, then that could add some more depth to playstyles.
* I didn't feel much difference between the pistol and the other gun (AK?). There may have been an increased fire rate, but I didn't notice.
* The art is simplistic, but then again, nothing wrong with simplistic. Besides, it still stands out.
* I think adding enemy variety would be a bit useful. It seems like the enemy can already chase you, so in future builds, why not add one that rushes straight at you with increased speed? Or have others use weapons like you do.
* I think adding trade-offs would be better than either absolute benefits or absolute negatives. For example, 'blam-up,' and 'damage-down.' Adds a bit more depth in combat while making encounters at least seem fair, though maybe your system would work better. Again, just personal preference.