The practice of hacking standard Super Mario World cartridges on stock Super Nintendo hardware has come a long way in a short time. Three years ago, it required a robot entering thousands of button presses per second to insert arbitrary code on top of the game. By last year, streamer SethBling was proving that this kind of code insertion was possible for a human acting with pixel-perfect precision.
Now, SethBling and others in the SMW hacking community have taken things a step further, permanently writing a full hex editor and gameplay mods onto a stock Super Mario World cartridge using nothing but standard controller inputs.
SethBling’s ten-minute video explaining the entire “jailbreaking” process is a must-watch for anyone interested in the particulars of perpetually altering a 25-year-old game without any special hardware. In short, the jailbreak builds on an exploit discovered by Cooper Harrsyn that lets players write data directly to the small, 256-byte save files that are permanently stored on the Super Mario World cartridge.
If you arrange that data just right, you can trick the game into running custom code just by loading the save file, saving you the trouble of manually jailbreaking the game every time you start it up. With that exploit in hand, Harasyn and SethBling worked together to create a compact, on-screen hex editor that could be loaded from one of the game’s save files. From there, players can edit the system RAM to alter the game state in a lot of ways, giving Mario arbitrary power-ups, messing with color palettes, or even beating levels with the press of a button.