Threshold 2P

Here is an unfinished project of mine to hack a classic title into a two-player cooperative game. I've had the idea for a couple of years now, and wanted to keep it under wraps until I had a finished game to show off. Unfortunately it was easier said than done.The idea was to bankswitch between two nearly identical copies of a game and to flicker two independent player sprites. The attached demo shows the basic idea. In this demo, player 1 can move freely, and player 2 is limited to horizontal movement. Despite my many z26 log traces, I never did figure out why a blank scanline runs through the second shooter at certain times.At this point, I've got enough homebrew ideas queued up, and this project is low priority for me. I'm posting up my work so far just in case anyone else wants to take a crack at it. Even if it's never finished, it's still a cool idea.Enjoy!