The classic sci-fi FPS Marathon from Bungie on Mac revived for modern hardware by the fan community.
This classic 1994 Bungie™ FPS had a foundational influence on the genre, and is now maintained by the fan community. Experience authentic game play using the original data files, with optional widescreen HUD support, 3D filtering/perspective, positional audio, and 60+ fps interpolation, just in case the original is too authentic.
Classic Marathon is powered by the Aleph One engine, which is available under the terms of the GNU General Public License (GPL) Version 3.
I forgot about Oni!
I remember I discovered it a couple of years after it came out as I was also discovering Ghost in the Shell—it felt like it could have been part of the same universe, had a lot of fun with it