I think it checks all the boxes for this bootcamp: key mechanics and fun. Here are my thoughts:
1. the background music felt invasive at certain moments. Like it was competing with the SFX of enemies and items.
2. Some sprites' animation felt strange. The main character's gun was constantly flickering. Not sure if that was intentional or a bug. The dark-wolf-demon walking looked like a cartoon with the rapid tiny steps, but slow movement.
3. It was unclear how close you have to go through enemies to lose HP. Some hits I should have received, I didn't, and in other instances, my HP loss was a mystery. I would solve this with a knock back on the character, or some frames of invincibility after a hit.
4. I was a big fan of the random power-ups you get while leveling up. I would add a count of how many I have collected and tag the uncollected ones as 'new'.