I just released my latest Godot project, a rhythm-based dungeon crawler a la Crypt of the Necrodancer. The entire game plays out in 16 x 9 pixels because of a dare from my game dev group. I've open-sourced (MIT) the code and project files. Of course, the music files I don't own aren't included in the Github project, but I'm releasing the game's hand-crafted pixel sprites under CC0. The Github page also talks about some of the tricks you need to make the rhythm part of the game play nice with the dungeon crawling part.
I love the way you describe the time travel aspect. My own project has to run on an NES, and memory constraints mean I can't actually store a previous game state entirely, so there are endless hacks and cheats to "rewrite history" after resolving most of the enemies in advance, to account for the player's actions at the last moment before display.
I can't cheat the beat timing though (drawing is way too slow) so I've got the beat judgement tuned to look less awful while being reasonably forgiving about late inputs. To compensate, I stretch out the animation timing on the following beat, so the early cels aren't weirdly bunched up after late inputs. It works well enough given the constraints.
It's fun seeing all the different approaches to this problem in the rhythm game sphere! It's way more complicated than you'd initially think, and games have all sorts of tricks up there sleeve to deal with it.
For more fun takes on rhythm games, check out this Roguelike Celebration talk from last year - some people in the Necrodancer community got together and added synchronous networked multiplayer (!!!) to the game. Black magic, haha, and it was a great reference when I was starting this project up.
https://www.youtube.com/watch?v=zwhNSbFVKQM
https://youtube.com/shorts/MNm4e5MxqFk?si=-UR3HayZOuDuhGJm
I actually gave a talk in 2023! It was about creating "proc gen" puzzles for a roguelite game. If you find a mathematical problem space where you can prove that every state is solvable, then you can just generate any set of starting conditions and let the player have at it. I don't have plans to present this year, but I'm working on some games that I hope will be worth a presentation in the future.
What software is most often used by these persons? I assume pico8?