The problem is newlib's sprintf() links to some odd system functions you wouldn't expect and which aren't available in the scope of the game. I don't recall off the top of my head what limitations --specs=nosys.specs has, but if the linker doesn't have any complaints it seems like it should be fine. I've got setup.c shims working for printf(), snprintf(), and asprintf(), like we have for malloc etc., will get those into a future update. I didn't include sprintf() since it's always better to use snprintf().. but I'll think about adding that too.