I always like to provide as detailed feedback as I can, so I'm happy to help!
The rooms where you had to chase the sorta blob sludge looking enemies around in a rectangle hall were a bit frustrating. I found especially as Leo it was almost impossible to stand in range of the enemies, and in an angle where you can shoot them without getting hit. The fact that the enemies explode into projectiles compounds the deadliness as there's very little room to maneuver and the hallways are quite long. Admittedly I may just suck at top down shooter, so maybe its me. But those areas were the ones where I seemed to lose the most health. In general its more like I would be ground down by several rooms and then die, rather than lose all my health in one.
The functionality of the menu and how its laid out I think can remain the same, its just the color scheme and maybe music choice that could help it fit the tone more. Like maybe have some background music that's a bit more aggressive, and have the menu elements a bit less dark. I'm just spitballing ideas, I'm confident you'll be able to sort something out.