I loved the crunch to shooting bullets! At first, I didn't realize that when the enemies slide, they're dead, so I kept shooting the dead bodies. The bodies didn't feel like much of a problem until difficulty 8 when they would act as a meat shield for enemies. :D
There didn't seem much reason not to press shift, so using AntiMicroX, I made shift toggle to be always on.
The music wasn't bad, but it felt like it went against the fast-paced gameplay that the game supported.
Indicating whether a level was safe or not was a nice touch. Starting back at difficulty 1 when the player character died felt pretty bad. Maybe rough-likes get away with it because most of them have procedural levels, preventing the player from feeling like he's just repeating things he's already done before.
I couldn't tell when/why I got hit very easily when a shooting enemy would attack me. If the bullets were a different color, they would stand out more?
The water ripples looked good. It might feel even more like water if it slowed you down or something else to affect the game.
Difficulty 7: Starting right off with a bang was fun, except that for the first few seconds, it's hard to know where the player is.
Would love it if there were a downloadable version! (I don't have internet at home) Also, a full-screen option for the web would be nice.
A fun game which I still have yet to beat... Looking forward to future development!
EDIT: Just noticed the health potions in the castle level. It's a lot easier now.