Start from Doom. Well, not quite the original release, but rather Doom Legacy. From this base, create a 3D Sonic platformer styled after the Genesis era games. That’s Sonic Robo Blast 2 (because yes, it’s a sequel from a previous fangame named Sonic Robo Blast from all the way back in 1997).
We’re not done yet. Mod it further… into an online kart game. That inherits the same modding abilities Doom Legacy has. You’ve got Sonic Robo Blast 2 Kart, sometimes nicknamed MUGEN Kart to the dismay of its developers due to the sheer amount of addons for increasingly weird characters its forum hosts. If you’re interested, said forum, hosting both the addons for SRB2, SRB2 Kart and the SRB2 Kart releases themselves can be found here (for some reason the main website is down as I’m writing this. Oops.)
For SRB2 Kart in particular, the thread to get your hands on it is here and you can find its repository here.
The game is wacky, very fun, runs on a stale potato and it’s easy to set up a server to subject an unsuspecting community to your specific choice of insane mods among the hundreds if not thousands available.
This seems to be a no strings attached good deal on xQc’s side. However…
Aaand the platform is doomed. Focusing on growth over viability is whats makes you a prime enshitification target.