Edit: I missed a couple key details in my read. They're clarified in the comments below.
Y2K is a prelude to the upcoming feature length TTRPG Cybermetal 2012. It's also an extremely strong release in its own right, and a great 1 player, 1 GM game.
The PDF is 16 pages with a great low-fi technical manual feel to its layout. Everything is clean and readable, but if this aesthetic were a movie, it would have VHS scanlines. It's a neat look.
Lorewise, in Y2K you play as a regular human on an earth that has been overrun by the forces of hell. It's the year 2000, there's no government, and demons and humans live mostly side by side in the only city you can get to. Guns have been made useless ever since people learned how to modulate the frequency of their consciousness, and people can install computer software into themselves for personal advantages.
Also a freeroaming computer bug is installing hostile AIs into people. Your task is to find and eliminate it.
Despite this Doom-y sort of setup, you're not particularly strong stat-wise. You have the sorts of abilities a normal person who lives side-by-side with demons would have, but you're not exactly an engine of rip and tear.
Y2K runs on a d100 engine, and your skills start at 50% and most don't go over that. To compensate, the game gives you a lot of leeway in how to apply your skills. Generally, as long as you can make a case for why a skill fits a particular task, you can use it.
Still, basic rolls in Y2K are a little more complicated than in typical d100 systems. You succeed/fail/crit on your d100 roll, but you also roll a d10 afterward for fallout. Fallout adds complications and bonuses irrespective of whether you succeeded or failed. So you can crit a roll, but also the situation slips further out of your control at the same time.
Combat feels a little hectic as a result, but you have lots of room to back down and go heal up. Hit Points are handled via Charge---a 0-100 system where taking damage at 0 Charge means death---but re-Charging is as easy as going back to your home. Damage is typically a d10.
Scenario-wise, Y2K comes with a tight map and a series of encounters that you can face while chasing the Bug. It feels OSR-y but also a little unfamiliar in a good way.
There isn't a specific chapter of GM resources in Y2K, but the game as a whole feels pretty GM-friendly. If you've GM'd Eclipse Phase or BRP or anything OSR, you should have an easy time here.
Overall, Y2K is sort of a teaser for the absolutely wild setting of Cybermetal 2012, but it's also a great standalone game. If you want something that feels partly cyberpunk, partly occult, partly like Doom set in an apartment block, I'd strongly recommend giving this a try.
-Page 5 mentions "gaining advantage," but it isn't spelled out if this works like advantage in 5e. Disadvantage is clarified on the next page.