The visual style is very cool. A mixture of pixel art and 3D is pretty rare. Environment is pretty chill too. While it’s a demo, it still has a good starting foundation.
I saw some complaints about the gameplay, specifically the boss, but understandably so. I can tell it’s not easy, and the most time-consuming part must have been the boss mechanics. The more patterns you want to give them, the more boolean conditions you need to manage in the code. If it’s hardcoded, the need for adding more conditions can grow really fast, might even need to reuse code across bosses to save development time.
Behavior Trees or Finite State Machines are worth researching if you’re curious about designing more bosses with more complex behavior (This is just my personal advice based on my experience coding bosses.).
Still, it’s a pretty solid game. Good job! A lot of love was put into it.