A year ago I got something going that worked on FCEU, but not real hardware.
I finally got motivated (by the 2011 NES coding competition) to revisit the code and see if I could get it working on real hardware.   I'm not sure if it does, but it finally works on Nintendulator.

Caveats:
-The title screen image was a freeware image I found.
-The first (and only) level background I did myself.  It accurately shows my artistic abilities or lack thereof.
-The beasties sprites are not mine.  I stole/borrowed them from Zzap.  I plan on doing my own.
- No audio.
- No scoring.
- No real point of the game.

It's more of a technical demo that I plan on making into some sort of game.
The title screen allow the idea of following the lightgun vertical position.
The game screen uses a binary tree to allow 8 different lightgun enemies to be targetted, with a blanking period of (I think) 4 screens.

Al

I was able to convert it from UNROM to NROM (using CHR RAM).

So now I just need to make it more than just a tech demo.
Al