Doom is the quintessential speedrunning game and, ultimately, that comes down to some of id's early design principles: Doom's WAD format ('Where's all the data?') made it easy for players to mess around with the game, and you could argue that the contemporary modding era began here.
The players who coalesced around and obsessed about one man's quest to slaughter lots of demons have done almost anything you can think of with the game, and one infamous oddity is called Nuts.
Nuts is a map created in 2001 by the prolific Doom modder B.P.R.D. While much of this modder's output is genuinely great stuff like Equinox , Nuts would become a trilogy of 'joke' maps. This being Doom, the joke is thus: Nuts contains 10617 monsters across two rooms, and is pretty much unplayable as a result.
One of the biggest elements of the joke, and a very important one for context here, is that even if you wanted to kill all of these monsters, you couldn't. The level gives the player a plasma gun and BFG, along with a bunch of ammo, but there's nowhere near enough to kill everything, particularly as the second room is stacked with high-health cyberdemons.
The map is notorious enough that speedrunners worked out ways to speedrun it anyway. The two main styles are a race-to-the-finish where you don't kill anything, and simply have to avoid being boxed-in by the enemies, and one where you kill as many enemies as possible before ending. The record in the latter category was held by Hurricaine Jr. with 92% of enemies killed.
Enter Doom speedrunner ZeroMaster. ZeroMaster had a theory, and in their own words here is what came of it: "Pain. I started working on this 4 months ago…"
I'm going to explain the run, but ZeroMaster did this around a year ago, and I found out about it thanks to the excellent Youtube channel of Karl Jobst, a former speedrunner who now makes in-depth videos about cool things that various communities pull off. His video is below.
ZeroMaster's idea was simple, but also not. In Doom, certain enemies will fight each other. "The issue with maxing this level is that even with really good infighting and perfect ammo management you are left with roughly 800 cyberdemons at 4000 health each," writes ZeroMaster, "and nothing besides your fists, which deal 2-20 damage per hit, to kill them with."
The cyberdemons are simply too chunky for the other monsters to make any kind of a serious dent in. "So there is only one solution," writes ZeroMaster. "Gather up enough homing revenant rockets to tear through all the cyberdemons."
The revenant enemy type fires rockets straight at the player, but also has a 25% or 75% chance (depending on spawn conditions) to fire homing rockets that follow the player. Their damage is also calculated within a range of 10-80 that averages out to 45 damage per shot. "850 cyberdemon at 4000 health," writes ZeroMaster, "[...] that means we need to simply gather up at least 70000 rockets, great!"
Here comes the rub. To gather this many rockets the player character is going to have to keep the revenants alive in the middle of the room by killing the barons (which would otherwise kill the revenants), then begin circling around the revenants to attract an ever-increasing trail of homing rockets. ZeroMaster estimated it would take about five hours. But that's real-time, and thousands then tens of thousands of rockets with smoke trails… yeah, we're gonna need a bigger PC.
The game begins running slower as the number of rockets increase, until eventually the player character is moving the equivalent of 0.5 seconds in every real-world minute.
"So in real time it takes about 23 days to gather the rockets, which would be extremely boring to do," writes ZeroMaster. But because the upper area of Nuts is so large, the speedrunner took a segment where they circled the area as this tactic required, then took these inputs and repeated them on a 6-hour cycle. That makes this a tool-assisted speedrun, and said tool took 23 days to run through the programmed cycle. Yes: somewhere in the world, unobserved, a little doom slayer was running around revenants for 23 days.
After this, ZeroMaster re-took control. "Then of course the fun part begins, where you are moving 4 frames every 14 seconds to guide the rockets to the cyberdemons. There's a few places where I do some weird things like take damage for no reason, which is because of just horrible controls (I can't even move backwards) and doing it over again takes at least 30 minutes, so I left it like that. I would have tried to make it a bit better looking, but putting in effort to do that would have driven me mad, so it'll have to do. It took roughly 20 hours to do 10 minutes, needless to say that is just an awful experience."
Almost unbelievably, ZeroMaster ran this on a laptop. They note that you could probably do this without tools, "you just need an actual super computer optimized to play Doom and about 6 hours."
I said Doom is the quintessential speedrunning game; and in some ways this absolutely bonkers achievement is an emblematic speedrun. Part of the fun of speedrunning is that it grew out of the gaming culture of setting your own challenges. Once you'd beaten a game, especially in the old days, you had to work out how to still have fun with it.
I mean, maybe 'fun' is going a bit too far here, but the joy for the viewer is in how overreaching and frankly unnecessary this is. It's one thing to think that you could possibly kill 850 cyberdemons with revenant rockets, and in so doing achieve what the Doom community thought impossible: Nuts was never meant to be 'completed' like this. It's a whole other thing to work out how you could actually do it and then, tool-assisted or no, pull it off.
"What an absolute waste of my time this has been," writes ZeroMaster, "hopefully you'll enjoy this more than I did." Take a bow my friend, because we most certainly did.