Thank you for making this cool game. I really liked it overall. I think Chapters 10 and 11 were a little too much for me though. I completed them, but it was frustrating and stressful, especially the last part of Chapter 11. For the rest I had a pretty good time. I am uploading my playthrough to Youtube but it's 9 hours and 31 minutes long so it is taking a while. (Edit: it is here)
This game really puts the "precision" in precision platformer. The jumps are so tight and unforgiving. This is not a complaint, just an observation. I often found myself thinking things like "okay, I need to slide a few pixels lower here" or "I should press left a few frames later after jumping off the wall". The small details of your inputs and motions really matter in this game, I think moreso than a lot of popular entries in the genre (compare with Celeste, which has a lot of forgiveness mechanics to give you a pass when you're slightly off target).
The unforgivingness is most noticeable with the orbs that give you an air jump if you tap the jump button while touching them. You have to be really precise with these. I don't know if it's because the hitboxes are small, or if it's because you're frequently whooshing past them at high speeds and only have a small window to hit them. A recurring challenge is having to jump off a wall, then immediately trigger one of these orbs to get a momentum-boosted air jump. I think it took me until around Chapter 7 before I started to get the hang of this. (Edit: Apparently you updated the game to make these a little easier to handle. Interesting.)
Speaking of momentum, the horizontal momentum in this game works in a funny way. Your character basically has "two momentums": running momentum and walljump momentum, which are tracked separately. Running momentum has instant (or near-instant?) acceleration and deceleration. Walljumping, though, gives you a burst of speed that decays over time. These two forms of momentum "stack" on top of each other; you can "fight" your walljump momentum using your running momentum, but you can't cancel it completely, you have to wait for it to decay. Alternatively, you can run in the same direction as your walljump for a super speedy long walljump. Some jumps are easier if you start with a "neutral" walljump and apply running momentum mid-jump. It's an unusual but fun way of jumping.
Mechanically, there is nothing really groundbreaking in this game: it's a hard platformer focused on wall jumping. But these little quirks give it a unique identity. The level design is excellent, featuring intricate jump sequences that require both good execution and puzzle-solving ability. And the art and music is so lovely. And I really love that you can play it with just one hand on the arrow keys (ultimate control scheme)