https://atariage.com/forums/topic/313776-nyd-2021/?do=findComment&comment=4714819

 Recently I found Zombies, a type-in game I played at the time on my VIC20 (my first computer), programmed by Mike O' Neill and published on Games for your VIC20, Virgin Books, 1983.


I decided to port it to Atari (my second computer). To port a game you should know both machines well. That's not my case but I made it nevertheless ah ah.


BASIC code is almost the same but zombies placement algorithm was too slow. Therefore I decided to replace the original with a better one made by DMSC.


Besides original version, with VIC20 character set, I added a version slightly faster and with new graphics made by TIX.


The program detects PAL/NTSC and adjusts palette.