I’m trying to find this one doom wad i used to play from doomworld that was a megawad ish, you start off in a warehouse in a suburb then the next map was being on a train where you need to board multiple ones while they’re moving then it’s a castle where you have to enter through an underground sewer tunnel and then it’s another warehouse esque town but with a port where you have to make platforming jumps with springs from sonic, then you face a boss of the authors sonic oc which consisted of being a blue tails that rapidly shot railgun projectiles at you, then finally the last map I believe takes place in a giant sky base with skybox graphics from Sonic 3. It was very Sonic esque but it isn’t Super Sonic Doom, I checked. Very similar though as they replace the skull keys with orange green and white keycards instead.