Steam also has mods released as standalone games and I wonder if it not happening recently is some change in Valve or just mod devs not reaching out to them. Enderal and Archolos are there, not to mention Valve's own old releases. I know many, many people found Enderal from the Steam release.

Nice, I hadn't tried searching for his name. I gotta try the rest of them eventually I only found Rolling Bird a few weeks ago.

And here's a few others I haven't played but happen to know about:

Endless Sky - store.steampowered.com/app/404410/E...

MekHQ - megamek.org

Simutrans - www.simutrans.com/en/

Kingdom: Classic - store.steampowered.com/app/368230/K...

Redpulse is another arcade-style banger, it's what it says on the tin, a no nonsense run 'n gun inspired by bullet hell games. Technically this might run under 30 minutes... if you are a superhuman and somehow beat it without dying or youjust use continue nonstop.

boghog.itch.io/redpulse

Rolling Bird (and I think the dev's other games) is free but has an option to pay just to support the dev. I haven't played Rolling Thunder which it cites as inspiration but it reminds me of Elevator Action. Very fun game.

store.steampowered.com/app/978800/R...

SideLine has a cool story, it's a borderline lost media DOS horizontal shmup being recovered with the blessing of the original dev

sideline.ghegs.com

There's also probably more free oldschool roguelikes than anyone knows of, some I noticed missing are Infra Arcana, Elona and The Ground Gives Way.

sites.google.com/site/infraar...

ylvania.org/elona_e.html

www.thegroundgivesway.com

I thought Unciv was only on mobile but it turns out it has a PC version. It's a free 4X game based on Civ V

yairm210.itch.io/unciv