I should point out that I have knowledge of implementing Action Replay/Game Genie hacks permanently into rom images by hex-editing the appropriate sections. So I was interested in trying to use this knowledge to implement the Japanese Credits cheat into Sonic 1 by default, and got an address from this thread, but it seems that goes way beyond the size of the rom itself. Searching around seems to associate FFFFxx addresses heavily with savestates. So can such codes only be hacked into savestates? I tried calculating an alternative address with the tip from this page, but to no avail. Thanks for reading.