I've merged in the initialization and display list builder code from 4K SpaceWar! 7800 and made the necessary tweaks to handle the moving zones. Fun! My main problem with this code was I kept running out of ZP RAM, which would push a (ZP),Y pointer variable to $FF, which doesn't work at all.

I first ran into the problem when I put in the initialization code and tweaked the display list initialization (so the constant parts of the tile headers only get written once). Kaboom! So I dragged out the EP code and started undoing changes with no success. Then I started anew and did one thing at a time. Step #1 - add ZP RAM variables. Kaboom?!? DASM really should warn you when DS crosses a page boundary....

Okay, so that's working. I need to write the code to create the last display list based on the first display list so top/bottom wrap around works. I also want to see if there's any cycles I can squeeze out of the display list builder code somehow then do a cycle count (ugh!).