Had an Atari 400 back in the day that's been lost to time. Recently picked up an Atari 800. Looking for an Assembly cartridge to pick up programming on it aga

Had an Atari 400 back in the day that's been lost to time. Recently picked up an Atari 800. Looking for an Assembly cartridge to pick up programming on it again. Finding a lot of interesting pdfs on 6502 processor specs that are out there : Atarimania is great for these: http://www.atarimania.com/documents-atari-400-800-xl-xe-books_1_8.html http://www.atarimania.com/documents-atari-400-800-xl-xe-book... Played Star Raiders with my son -- that was awesome!