I've got most of the main controls! Z for Mario, and X for Luigi, or press A to make them jump at the same time. Press C to switch to the jump option, and press V to switch to the hammer option. The option to jump on to platforms is not in game yet, We're working on that.
Thanks to @SpideyPlaysMC for most code and sprites, the rest is by me. Logo design by me and @Matsnat64. This is unfinished :P And I was board so I shared it, maybe you can finish it :P
