this was awesome. I can't believe you were able to pull this off. I am a huge fan of the "boomer shooter" and I love that you brought it to the NES. It runs really smooth too, I have no idea how you did it.
I know this is a proof of concept, but I feel the 3D enemies and height differentials make it a little confusing. I feel like having it be single plane with sprite enemies (like wolfenstein 3d) would have made it much more playable for longer periods of time. I got lost pretty easily and didn't know what was a hill or a wall or an enemy, it all kinda smooshed together.
Still, so much potential here. I'd love to blast stuff in an NES FPS. Awesome job