@Felthry It's a mod for (OG) Doom/Doom 2 called "The Golden Souls 2" which is a mod to make Doom very Mario themed. The first one was rather small, but did an "ok" job at being a Super Mario 64 style version of Doom (still keeping the core gameplay of Doom mind you, but had some very mario-esque maps and the castle hub and such), whereas the second is more "Super Mario World" styled with a level map and everything, and more mario styled in gameplay too.

Still can't jump on enemies tho ;w;