This game has an awesome concept in building your own programmable powerups. Initially, it was a bit frustrating since I didn't know what each one did, but got more fun as I learned about the different parts and what they did — maybe you could include a manual with their different effects if you pursue this project further. The different enemy types provide a good variety of challenge, and the randomly-generated arenas keep things interesting, though there were times when I got stuck in parts of the arena that were too deep for me to jump out of.
One thing I am confused about, though: what do you mean by the game's era being the 2000s? To me, it looks a bit like a Pico-8 game.