Really cool game and moody vibes!
Thoughts I had while playing:
- wish I could switch to the next level without having to go all the way back to the door - that part often takes longer than beating the level does!
- wish I could upgrade attack range
- often the enemy & enemy shots were the same color as the player & player shots, I'm guessing that's for style, but this made it a little difficult to differentiate sometimes
- I like the little background elements adding flavor to the scene, especially the one that mirrors your movement on floor 8! *spooky!*
- dang! I lost pretty suddenly... I thought I had nearly-full health, but maybe I got hit with a ton at once... or maybe there's a hidden sinister countdown like you mentioned in the notes ...that I failed to notice, lol
- I was really happy to see the Continue button, but, it restarted the game to lvl1 anyway! :[
- UI elements were pretty small on screen, it was hard to read some of the text - here's a screenshot:

Great work!