Awesome effort, looking forward to playing this! I found it crashed after the first level, and also crashed if I tried to enable 128 mode - using real hardware and a Kung Fu flash cartridge. Is Kung Fu flash fully supported?
I'm having issues with the kungfu flash as well. No crashes. It loads up and plays fine. Up to level 8 so far. But when it writes the save data, either new file or overwrite existing, and it reduces the file size (to 524kb) and no progress is saved. Run it again after reset or power cycle and it still loads and plays fine. Just no saved progress.