A big difference between Hexagon and most other rhythm games like Stepmania, Beatmanias IIDX, Guitar Hero, etc, is that pattern is the same. Just like musicians memorize complex music that they later perform[1] with precise timing, the same is possible for these step/note patterns. I've personally seen someone perform one of the insane speed/note-density DDR songs blindfolded. Humans have surprisingly good internal timing and mechanical ability, iff you can memorize/practice it before hand.
Super Hexagon doesn't allow any of that. The game is randomly generated each time, making memorization impossible. It's 100% reaction against the incoming wall pattern, with no pauses. Except you don't actually have time to "react".
I recommend this[2] essay that does a much better (and more poetic) job of explaining how uniquely Supper Hexagon interacts with human perception.
Rhythm games are not about memorization, unless you call pattern recognition and muscle memory memorization.
First of all, players don't need to memorize the charts. Take a good player, give him an entirely new chart and he will perform much better than any beginner ever will, even with memorization. Shuffle mode, where the notes are mixed and therefore can't be memorized is just a minor handicap. Much, much easier than memorizing a whole song.
There are two things at work here.
The reaction time is actually not that short. For high level play, players typically set notes to appear about 500ms before action. At that rate, anyone can hit a single note, the difficulty is that there are lots of them.
The difference between experienced players and beginners is that experiences players recognize blocks instead of single notes, just like you read entire words rather than individual letters.
Super Hexagon is akin to "sight reading" or performing music "a prima vista", while DDR as played by most players is a type of rehearsed musical performance (or, well, dance, I suppose).
Being able to play a prima vista is a rather specialized skill even among musicians; I've only known a handful of people who can do it really well. I don't think it has a ton of utility (at least I never found it to have a lot) and so it's not something that many people actively develop or train, though.
> I've personally seen someone perform one of the insane speed/note-density DDR songs blindfolded
Rock Band 4 has a "Brutal" mode where notes are almost completely hidden save for a slice of a millisecond at the top, but although it does give a hint of an information that may be processed in the end it mostly doesn't matter, since at that point you can effectively do it blindfolded, which is as a process no different to learning to play the actual song.
Music video games can easily thwart the pre-memorization with the randomized chart (often considered essential to master the game). Players typically learn the timing, but possibly not the entire patterns. It is still remarkable that top-ranked players can do much, much better on a new song at the first glance---probably because the music is much more predictable than the pattern itself, so one can guide the pattern recognization with the music.
While the order of the walls in Super Hexagon is random, each level has a predetermined set of walls. Once you identify which wall pattern is coming you know exactly the maneuver needed to traverse it.
This makes Super Hexagon more a game of quick pattern recognition than reaction time.
When I play it I am generally focused at the edges of the screen to quickly identify the next pattern and only using my peripheral vision to maneuver around the walls in the center.
You are missing his point though. It's not just memorizing the whole song. If it was, when you play a _new_ song, you'd be as rusty as when you first started to learn to play.
But new versions come out, with new sets of songs, and people play songs of the same approximate difficulty as well. If it was simply memorization, they wouldn't be able to play same or near difficulty songs. They'd have to "ramp up" as they memorized the new song.
Obviously, people's brains are reacting to similar patterns (each song has a "style" and many songs are of the same "style" with things like jumps, diagonals, triplets and so on), as well as other subconscious neural reactions.
When you're playing 9-step (out of 10) step songs, you're not watching individual arrows at all. It'd be impossible. You unfocus your eyes and play through your peripheral vision. Your body reacts. You don't need to think at all.
(So nobody is arguing that the Hexagon game isn't "more random" . They're arguing that it's more than just randomness at play.)
It's really no different that carrying on a conversation while playing a game of casual pong with a friend. Everyone just calls it "muscle memory." The pattern is never the same with a ball bouncing off a table. It's not rocket science.
Super Hexagon doesn't allow any of that. The game is randomly generated each time, making memorization impossible. It's 100% reaction against the incoming wall pattern, with no pauses. Except you don't actually have time to "react".
I recommend this[2] essay that does a much better (and more poetic) job of explaining how uniquely Supper Hexagon interacts with human perception.
[1] https://www.youtube.com/watch?v=JRUwpUqSFbI
[2] https://problemmachine.wordpress.com/2015/04/11/hexagon/