Hello!
Overall I had a good time with this demo. I like the main gameplay gimmick of having to master the level as you go with checkpoints and recursion flags. If the game was longer I would probably want more of this format with three recursion flags making up a level and intermittent checkpoints. I think that will allow a good difficulty ramp without making the levels too arduous to complete. The player controller was good for this format of game. It might feel a bit sluggish if you weren't trying to get a good 'flow / line' going with the run but if you are pushing for speed it felt okay.
I might look into changing the dash key as Z and M felt a bit awkward for my hand position, otherwise UI and controls seemed fine. Maybe consider putting them in the background of the first level as I had to look at the controls menu to discover I has a dash mechanic. I am generally not a fan of un-skipable stuff and you intro sequence was quite long as was the menu scene transition on restarting after I finished the demo. I would either make those shorter or skipable in some way. Maybe a way to fast forward the text scroll in the intro?
I liked the art and music. The music was very nice and the sound effects were good. The player idle and run animations were nice. A background plate with some dark grey texture could make the environment feel a bit more finished.
Our team have submitted an action-oriented platform runner if you'd like to check it out (Link below). :)
I wish you the best with your projects!
https://itch.io/jam/feedback-quest-8-indiegames-x-indie-streamers/rate/3773442