Sweet! Does anyone have a list of high-quality open source games like this?

(Subjective interpretation, but something like, "I couldn't believe it's free, I would have paid for it anyway.")

Cataclysm: Dark Days Ahead: Like Dwarf Fortress but post-apocalyptic survival horror. Endless Sky: top-down space shooter inspired by Escape Velocity SuperTux: inspired by Super Mario SuperTuxKart: inspired by Mario Kart https://en.wikipedia.org/wiki/List_of_open-source_video_game... and https://en.wikipedia.org/wiki/List_of_commercial_video_games...

Well:

- Supertux2, it got recently revamped, the quality skyrocketed. Much better controls and artwork.

- Supetux Advance, this is really great too.

- Retux (More Wariolike than Mario)

- Nethack/Slashem. A Roguelike more bound to interaction/exploration/mechanics than combat, but Slashem makes combat crazy with the Doppleganger Monk, which is basically a Shonen Manga, the role. (Dragon Ball/Naruto depending on your age).

- DCSS. Basically, not Nethack/Slashem, much more combat oriented than the Slashem combinatorics playing with the Monk a la Jackie Chan, this is more like an ARPG made a Rogue.

- Frotz/Lectrote/Winfrotz/whatver Z Machine interpreter and "All Things Devour". Spiritwrak, too. Great libre text adventures and still enganing because of weird mechanics.

- Frozen Bubble

- OpenArena.

- FreeDoom, better compiled with Deutex on daily builds.

- FreeCiv.

- OpenTTD today can be standalone enough.

- Frozen Bubble

- Minetest+tons of subgames such as Glitch, Nodecore...

- OOlite

- Speed Dreams. If the controls are hard, try the arcade mode. If the controls are still hard, get SupertuxKart, pick some real life car from the addons and get all the SD tracks from the inline downloader, they are several.

[deleted]

OpenArena even has a browser version these days but sadly it doesn't seem to have any active servers anymore. I had progressed to the point where I could strafe jump and rocket jump all day.

Not Open Source but still/now free to play (these are my favs, I played them through back and forth):

- Trackmania Nations Forever (e.g. via Steam) - https://www.youtube.com/watch?v=aj2u2OrZ2vI

- Starcraft Brood War - though I have not tested it via the battlenet.exe, played it when it still was payware.

- Gemcraft Labyrinth - played it when flash was a thing, but now it is again, e.g. on Armorgames

And, I got games like Portal 1 & 2, Outer Wilds, Osmos, Manifold Garden, Planet Crafter and many more for under ten, some for under five Euros each when they were on special offer on Steam. I once got Just Cause 3 for three Euros.

The Free Civ and Free Colonization games are good. Brogue, Nethack, DCSS are good if you like roguelikes. OpenMW is a totally open source reimplementation of Morrowind, so that might fit the bill.

If you like arena shooters, Xonotic is quite remarkable. https://en.wikipedia.org/wiki/Xonotic

Oh, yeah! And I believe there are not many games which have Linux, Windows and MacOS versions allowing interplay. Several years ago we had one or two LAN parties with hardware running all three operating systems.

Mindustry is worth a look if you like factorio and tower defense: https://en.wikipedia.org/wiki/Mindustry

Edited to add:

If you like RTS then Beyond All Reason is fantastic: https://en.wikipedia.org/wiki/Beyond_All_Reason

I know it's a very niche domain, but I feel this way about Lizard.

My lizard is the lizard of website: https://rainwarrior.ca/lizard/

My lizard is the lizard of source: https://github.com/bbbradsmith/lizard_src_demo/

OpenRCT2 is a reimplementation of RollerCoaster Tycoon 2.

Just like its cousing OpenTTD which is a reimplementation of Chris Sawyer's Transport Tycoon.

Luanti aka minetest

Widelands as a settler clone

0ad https://play0ad.com/

My first reaction was exactly that; I can't believe it's free!

Endless Sky, GPLv3 space trading game. Being a space trucker is dangerously addictive.