Really nice little platformer (Celestelike? Meatboylike?), especially for 3 days of effort.
Had nice music with a bit of variety in the loop and sfx and a very impressive amount of visual juice in the character movement, the backgrounds, screen transitions, etc. Well put together.
I feel like it's basically impossible to balance a precision platformer during gamejams because the developer just gets so good at it during development, but I think the difficulty here was well done with a nice smooth curve. It never got overly frustrating and I never felt like I died from something that wasn't 'fair'. The checkpoints being at the start of each screen was a great decision as well, imo.
If I had any feedback it would be incredibly minor tweaks and entirely personal opinion around things like, maybe pulling the collision of the spikes in on the sides so there is some grace if your touching the side (As opposed to the pointy end), and maybe increasing the accel so that you get to full speed faster to stop overshooting.
In in all a really strong submission, great work!