Strawberry jam for celeste. It’s a huge collaborative project that introduces 100+ levels (base game has 25) with a really wide range of difficulties, graphical styles, new mechanics, original music and ideas on par with the quality from the base game. Definitely a must play if you like 2d platformers

You could try lunacid, it’s not old but definitely old style.

I know it’s not what you asked for but i think you would enjoy the doom games, specifically eternal but 2016 is also great.

It has great campaign, great music, arguably the best combat system in a shooter game, it’s highly replayable, 20€ with all the dlcs when on sale and when played on higher difficulties it becomes extremly technical.

It also has a multiplayer mode but i don’t know too much about it

“Can’t live without electricity”

Basically routing a pcb with extra dopamine