The tree that is old-school fps goodness just keeps on giving: https://store.steampowered.com/app/1409460/Brutal_Fate/ Sgt. Mark IV - the creator of Brutal Doom - is creating a game of his own! Similarities to Brutal Doom are evident but that's not bad at all. Possibly he has wanted to make this for a while. Likely runs on the GZDoom engine too. EDIT: yes, GZDoom engine (from Steam page): Mod it until it breaks. Running on the highly reliable GZDoom engine, this game is extremely easy to be modified. You can make mods adding custom weapons, enemies, levels, and entire new user-made campaigns. Also a bit of info about Early Access (from Steam page): How this game will work on Early Access? You will have a demo campaign of about 6 to 8 levels and 2 boss fights, and at least one Horde Mode map (where you must defend an arena from waves of enemies). A free 2 level demo will be included on the same day Early Access launches.As days goes by, the Early Access builds will keep geting more levels (generally Horde Mode levels, because they are the best kind of levels to test the gameplay aspects of new weapons and monsters being added), and eventually in 2022, the game will receive a full launch with it's main plot-driven campaign. Personally will grab this as soon as available (Early Access January 2021).