lovely pixel art! very fitting sfx, my only suggestion is that the jump sfx would benefit from some pitch randomization to break up the monotony. I think the music for the platforming part is a bit slow, but it fits the mood well enough. the boss music absolutely slaps!
that aside, gameplay is king, and this game really nails it. I read some complaints about the controls in the comments, and I suspect it’s because of how horizontal momentum is preserved while airborne. precision platformers usually have automatic deceleration when no input is held, and momentum-based platformers rarely require any precision at all. personally, I love this style of air-control, even for precise movement. it gives a lot of control over the jump arc: tapping left or right adjusts the trajectory, and not pressing anything simply maintains the trajectory. for this game, it makes it easy to match the velocity of the rolling balls — that would be pretty annoying with the more common “automatic deceleration” control type. maybe some of the numbers could use some tweaking, but the current controls feel really good in my opinion.
the core gimmick is neat, and the level design sets up for some interesting situations that are fun to figure out and execute. the level clarity was a bit lacking at first, but it was no problem after figuring out the properties of each tile type. my only real complaint about the platforming is how long the death/reset transition takes — it looks great, but it takes almost 2 seconds from dying until I regain control, and I found that long pause to be kinda jarring.
platforming aside, it was nice to see a boss fight to shake things up. however, it’s very punishing, as there are no checkpoints and a single hit resets the entire fight. that said, it’s an awesome boss fight, I just think it could be a bit more lenient.
overall, this is a really solid kaizo-like platformer!