Terrifying Rhythm Games
Most gaming communities have at least one subgroup that can charitably be called masochists. You know the type: they beat the hardest game in the genre, then 100% it, then declare it wasn't hard enough and mod it so that it kills you instantly upon making eye contact with the screen.
I'm one of those people. Specifically, I'm one of those people for rhythm games. These are games that make you push buttons in time to music- can't be that hard, right? It's music! There's only so many notes you can make a button for!
You underestimate the hardcore rhythm gaming community if you think you're not about to suffer.
NotITG
You've probably heard of Dance Dance Revolution by now. It's a rhythm gaming classic that's passed through most arcades at one time or another, and it's kicked off a massive number of clones and spinoffs. One of these derivative games is In The Groove. Functionally, it's the same. You've got a dancepad, four arrows, and some music. It might as well be DDR under another name (and I've probably pissed a few people off by saying that).
As tends to happen, someone thought it was too hard to make custom charts for In The Groove, so they made OpenITG. Functionally the same game, but with some tweaks under the hood to make it far easier to make custom charts. As a bonus, it's open-source!
Someone looked at OpenITG and thought "this is still too easy. I want to torture people." That led to the creation of NotITG, a derivative of a derivative of a derivative that's designed for some of the most ridiculous modcharts I've ever seen. I adore it.
What's that? You want to see some of the bullshit the community's come up with? Sure!





Taro4012 even recreated Baba Is You in the middle of a chart:

I can't emphasize enough how much this game embodies this side of the community. There are regular sight-reading competitions of charts that most people can't see a single note in, and the folks who play in these competitions nail them on the first try. The charts get harder every year. People recreate other games in NotITG, force players to do math mid-chart (yes, really), and then find yet more ways to make the game harder. In short, it's glorious, and I'll die screaming because my legs hurt trying to keep up with these charts.
Thumper
Thumper is described as a "rhythmic violence game" by its developers, and that's the best description of it. This is a game that feels violent despite a complete lack of traditional fighting, blood, gore, or any other staples of action games. The premise is simple: you're a beetle-thing hurtling down a track. Hit spacebar and/or arrow keys to respond to things on the track so they don't smash you to pieces. In practice?



Good luck seeing the notes before they hit you!
I think the best way to explain the sheer terror of playing this game is with a personal anecdote. I've beaten Thumper, and it took me months. Towards the tail end of the game, I was playing a level as usual. A popup from Windows "helpfully" interupted me (I don't miss those!), but the game kept going. I couldn't stop playing even though the whole center of my screen was blocked. Despite that, I finished the level without issue because this game forces you to read as far up the track as possible. I was never looking at the center of the screen. If I looked at the center, I would die.

And you can only be hit twice before you have to restart the section. Sure, you can heal by pulling off a very specific manuver at the right time, but in practice? Any healing you get is by happenstance. Half the time is spent hanging on for dear life and praying that your reaction time is up to the task. The other half is spent swearing at a metal ring, demon head made of teeth, trippy starfish, or a giant glass pyramid. I'm not kidding.


Surprisingly, there is a modding community for this game despite there not being a level creator or mod support in the game. Folks managed it anyway. The results scare me.
In short? This game is 10/10 and will scare the crap out of you in the best way possible. Prepare to suffer.
Rhythm Doctor Custom Charts
Rhythm Doctor is a one-button rhythm game in the spirit of Rhythm Heaven. It demands not just accuracy, but precision. There's not much tolerance for error. Despite that, it's a pretty simple game to play, and it's worth giving it a shot if you haven't already. It's got some great commentary on how the medical system screws everyone over.

It also comes with a level editor.
Technically, the level editor came out before the game itself, so there were a slew of custom levels well before the game itself came out. The community started strong and just kept going. People have turned this game into something unrecognizable, and I have no idea how they did it. We have the same level editor. I looked at it. I looked at their charts in the level editor. I still have no idea how people managed some of the things they've made.



ADOFAI Custom Charts
This is another one-button rhythm game with a simple premise. Two balls rotate around one another, "walking" along a track of tiles. Hit a button when they touch the tiles. It's a somewhat unique premise that's given rise to plenty of custom levels ranging from pleasant to horrifying.
Allow me to introduce you to Galaxy Collapse.
Specifically, the nerfed version. The original version is probably outright impossible. It's yet to be beaten. The nerfed version was beaten, albeit only after Gamma Loop spent three months running the chart more days than not. He cried when he finally beat it. It's that bad. Screenshots can't capture the terror of this one- follow the link and see for yourself. All I can do is give tiny slices of a ridiculously demanding chart in hopes of getting the general idea across.


I'm beyond impressed that anyone cleared it, let alone cleared it without checkpoints. I'd cry too after managing that. There are plenty of other charts that are similarly difficult, and after the recent DLC opened up the possibility of three balls instead of two, I'm sure charts will only get harder.
Phigros
I'll be up-front and say that this is my all-time favorite rhythm game.
Occasionally, a group of developers will get together and agree to make hardcore rhythm gamers suffer- and like the masochists we are, gamers eat it up. This is one of those games. The target line moves. There are often multiple target lines, all of which are moving. The high-level charts will use every finger you have. Notes will fake you out or mess with you. Sometimes, notes are the targets. There are even a few convoluted chart unlock paths- to unlock one specific chart, you need to perfect the last song in a section, return to the first song in that section, and miss 5 specific notes that aren't normally in that chart (and only those 5). Then, you need to pass 2 more charts before you get a chance to unlock a chart. You have to get a C rating or higher to keep it, and it's notoriously brutal to play. This game doesn't hold its punches.


Even more impressively, the developers seem to be keeping tabs on common player tactics. It's become common for players to catch a certain type of note by holding their whole hand down. The developers started making charts that not only forced players to use this tactic, but used it against them as a way of taking a hand out of play. They make April Fool's charts every year, and they've gotten progressively more absurd to keep up with the playerbase's improving skills. 2022's was wild enough that I felt winded sightreading it because they threw every game convention out the window in a way that worked. It was glorious.

Did I mention that this is a free mobile game that's never shown me a single ad or forced me to pay money for it? Yeah. It's incredible in more ways than one.

Credits
NotITG
Thumper
Rhythm Doctor
ADOFAI
Phigros
Written .