Many years ago I mentioned that long-lost RTS classic Warzone 2100 had been resurrected and maintained by a stalwart group of fans. That project is ongoing, with a new update arriving this week. Warzone 2100 3.1.0 appeared yesterday and "brings along over 2 1/2 years worth of bug fixes and improvements." There are Windows, Linux, and Mac versions.
Warzone 2100 was notable for its early use of 3D, and stood next to Ground Control in the first round of the 3D RTS wars. It also had an awesome tech tree, of the kind games today only deign to imitate. I've dun up the old-fashioned CGI intro video for your perusal below. Oh how things have changed/stayed the same.
Warzone 2100 was a sort of defining game for me. Sure, Ground Control was prettier and slicker, but Warzone already had me by then, with its huge artillery salvoes and meticulous production fiddling. Oh, memories. I am so very old.