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Mindustry is neat if you like tower defenses and factory/automation games.
[edit] Though this isn't exactly a game, I thought I'd mention it: The Powder Toy. Really fun physics-ish sandbox game if you like just playing around with little particles or making electronics or nuclear powered fireworks shows, etc.
This was the first thing I thought of when I saw the title of the post. Mindustry is awesome, I got so addicted to it for a bit haha
Mindustry is great! I've put a ton of hours into it and I've gotten my kids into it. Super active dev and good community.
I prefer it to factorio
Open source game based on Transportation Tycoon Deluxe.
I wish it had a modern GUI though. The old one is almost unusable even though they've made an attempt to implement DPI scaling.
Not a very original answer, but I still enjoy The Battle for Wesnoth after many years.
Mindustry and Shattered Pixel Dungeon, I played those a lot of my phone but haven't done so in quite a while! I think both of those are available on desktop Linux too, Shattered Pixel Dungeon even works on my Linux phone.
Yeah, Mindustry is cross platform and available on Linux too. Love mindustry, such an awesome game!
It's pretty basic, but I'm going to say SuperTuxKart as a must if you are into kart racers (especially since I don't know any others).
I also recommend the still in development SuperTux Advance by Kelvin Shadewing. It's similar to just plain old SuperTux but has unique levels and more playable characters that will have different abilities (probably still mostly locked behind debug for them).
3 out of 4 begin with "Super"!
Beyond All Reasons. It’s a spiritual successor of Total Annihilation and Supreme Commander using the Spring engine.
It’s also a great game in its own right, especially the various advanced unit positioning and selection features had me amazed. The graphics are good and the performance with many units is finally very good too, after some patches last year (or two years? I don’t remember).
If Roblox counts as a game instead of a platform, then I guess Minetest also counts as an open-source game.
ScummVM works really well in linux, if youre a fan of classic point and click adventure games.
Running on that VM, I really enjoyed Flight of the Amazon Queen a few years back. Warning: it's an oldie containing lots of sexist moments - I'm not sure I would enjoy it as much today.
Currently Endless Sky! Although I haven't gotten far, and playing without mods, I love the vibes
Unciv is open source civ5
@sleepybisexual DOOM! The source code is open source, but the assets aren't. So this might be a bit of cheating reply. https://github.com/id-Software/DOOM
There is a complete set of free assets, in the form of Freedoom. Also, the official Steam version is closed-source, so make sure you're getting a free source port. (Most distros have a few in their repos, and Freedoom+GZDoom is also in Flathub.)
@ipacialsection Ah yes, I should have mentioned Freedoom! Thanks for the link, totally forgot about it!
I've dumped more hours into OpenTTD and Zero-K than I care to think about
I haven't played in over a year, but I really spent some hours in Veloren the last time I picked it up!
Xonotic is one that i would reccomend heavily, and it's an arena shooter
I remember trying it a long time ago, and it was pretty fun.
I am on Mobile (aka lazy), so no link. Simutrans for me, beats every other transport sim. The organic growth of cities and industries that happens while you build and optimize your transport systems is one of the many features I like so much.
I highly recommend playing Doom with the Crispy Doom source port and the Freedoom data files.
For something more modern, Xonotic is about the best-looking FOSS game out there and an excellent multiplayer arena shooter.
Cortex Command Community Edition
When I did play foss games, I played battle for wesnoth, teeworlds, minetest, super tux csrt and openarena. Lsst one might be dead due to being a mainly multiplayer game.
Nethack! It's basically the original roguelike, if you liked shattered pixel dungeons then you'll like nethack. There are also several other open source rogelikes to check out as well... including the original Rogue!
Are there good UIs/tilesets for Nethack these days?
Warzone 2100. 3D RTS from the late 90s that was open-sourced after the studio went belly-up. Fantastic game, runs on even ancient hardware.
In terms of games I actually play, Cataclysm: DDA (even if I still suck at it after hundreds of hours).
In terms of technical/visual impressiveness, Veloren.
Tremulous is a free and open source asymmetric team-based first-person shooter with real-time strategy elements. The game features two opposing teams: humans and aliens. Each team must attack the enemy’s base and team members while defending their own base. https://tremulous.net/
Currently downloading but is it still active? Is there still a player base?
SuperTuxKart is really good with friends.
VVVVVV. It's not GPL though, so technically it's not open source, but source-available.
Note that while the source code is available, the assets is not, so you'll still need to buy the game here: https://store.steampowered.com/app/70300/VVVVVV/
There are many things that use a license that isn't GPL that area still open source. I haven't looked into this one past the fact that it's a custom license though. So it'll probably depend on your definition of open source.
I really enjoyed Minedustry. Also, does Katawa Shoujo count?
Cataclysm: Dark Days Ahead is pretty astounding, offering an incredible level of detail and degree of freedom, plus just lots of zombies to fight.
I haven't messed with an open source game since early Sauerbraten. I gave up because of the crazy learning curve to git gud.