Gex The Gecko in Sonic 1

This is a ROM hack from the 2020 Sonic Hacking Contest, combining the mascot from Crystal Dynamics' Gex series with the original Sonic the Hedgehog on SEGA Genesis. It's a character-swap mod that replaces Sonic's sprite and some audio with Gex the Gecko, turning the familiar Green Hill Zone into a completely different visual experience. The entry was submitted to the contest under the title "Gex The Gecko in Sonic 1" and remains a novelty crossover for fans of both franchises. The core gameplay follows the same structure as Sonic 1: you run and jump through side-scrolling levels, collect rings, defeat badniks, and try to reach the goal post at the end of each act. Controls are identical to the original - the D-Pad moves Gex, a button jumps, and holding the button while moving lets you roll into enemies or through obstacles. Since it's a hack, the physics and level layouts are unchanged from the base game, so anyone who's played Sonic 1 will know exactly what to do. This hack is worth a look if you enjoy seeing classic characters dropped into unexpected places. It doesn't add new levels or mechanics, but the sprite work and audio tweaks give the game a different personality. It's a simple, well-executed character swap that fits right into the tradition of ROM hacks from online contests - not a major overhaul, but a fun curiosity for anyone who remembers Gex or just wants to see the blue blur replaced by a gecko in a cartoon suit.