So after I finished The Rat mouse it seemed like time to revisit the Diecom Light Gun interface. Two years ago Joe Zbiciak shocked me by suggesting that the the interface needs to be polled once every scan line, not every frame like I had thought.
Then after I had dissembled the supporting code from the game Iron Forest. I discovered the the device was not being reset on every scan line. It turned out there wasn’t enough time time during the the horizontal refresh to cycle thru all sixteen states.
But Joe reassured me that it just meant that there was a constant drift that should be eiasly accounted for. I am in the middle of that problem right now and have should have it solved soon.