If you're looking for a shooter, co-op campaigns for those things dried up a while back, so you're mostly looking at older games. My friends and I are playing Quake and Quake II to scratch that itch, but those old shooters are also very maze-like. If you're open to suggestions beyond shooters, I'd recommend a couple of roguelikes, namely Streets of Rogue and Vagante. Both are very chaotic, sandbox-y, challenging, and scale really well for co-op.
The Half-Life franchise, maybe. Half-Life 2 and up has a lot of physics stuff including the Gravity Gun, but considering HL1 is free to play via Sven Co-op it wouldn’t hurt to start there. You’ll need something like Synergy or Obsidian Conflict to play HL2 cooperatively.
The borderlands series. Start from the first and work your way through the franchise. I’m not a huge fan of the latest games but 1 and 2 have at least 60-80h of gameplay I’d say.
Gears of War comes to mind, not much physics but a lot of emphasis on movement but in a different way from Halo, still stupid fun to play the campaign Co-op!
Ditch Windows and install Linux and Steam, then add your game to the library as a non-Steam app and use the compatibility tab in the properties menu to force the use of the Proton compatibility layer. You should then be able to run the game through steam as normal. This has worked for me with almost all my old games and will probably work for you too.
Add the setup/installer executable as a non-steam game, run it to do the install, then modify the non-steam game’s settings to point at the installed executable so it can run from the directory where it is installed.
No problem! I’ve used this trick to run non-game Windows apps on the Steam Deck too, though support can vary wildly.
As an alternative, you might also check Lutris, which employs user scripts for installing and running Windows software in Linux. You can even add them to Steam so they’ll work in the Steam Deck’s gaming mode:
I haven’t personally tried using the tools in this video, but they may be an easier way to set up virtual machines for specific older hardware/ windows machines for gaming.
I’ve gone through this song and dance before with my old games and the most success I’ve had is with wine on Linux. It’s not foolproof unfortunately, and takes a bit of tinkering. It likely won’t work for every game either. You’ll probably want to find tutorials for each specific game you’re trying to run. Another option I’ve had some success with is running a windows xp VM. But again this isn’t foolproof and requires some technical literacy
Check each game's entry on PCGamingWiki. They're a good resource for finding what it takes to get old games running well on modern PCs. A lot of times, the answer is either "buy it on Steam and use a community-made patch" or "buy it on GOG".
I'm curious, what games are you trying to get working?
As others have said, you’re in that pocket of time where the game wants more than DOS, but less than modern windows, which isn’t well catered to. Your best option is a windows 98 or 95 virtual machine, which is doable, but not trivial or quick to set up.
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