Game Review Time
What I liked
The thing that stood out to me the most was the visuals, the simple monochromatic pallete mixed in with shadow work make the game stand out and generally looked pretty good. The occasional particle effect was also stylistically nice. The controls felt tight and responsive and the general theme was respected and explored in a meaningful capacity. I also enjoyed the little bit of animation for completing a level.
What I didn't like
What kills you isn't always immidietly obvious. I thought the first couple of times I tried the spinning Cross level that only the spiked could kill me. Whilst the levels were well design the difficulty ramp up was a little sharp towards the end. Overall however in terms of difficulty you explored a vertical slice of the design space well enough. I didn't like that the collectibles reset after death, though this I believe is just personal preference.
Potential Improvements
A tiny bit of dust trailing behind the player or appearing when they lands would be pretty nice. Post processing to add a tiny bit of bloom would also improve the game quality overall for visuals and would crispen the contrasts you're trying to establish ironically.
Overall Thoughts
This was a very well designed platformer, with a good control scheme. The levels themselves were considered and I didn't find any major or obvious bugs. The game has space to expand and some room for polish, but it's overall a very solid entry, great job.