Congrats on finishing the jam! I think the art is very nice and the little character designs were good. I like the UI in the top corner and the art itself is very clean. It certainly looks like a brain!
I had a lot difficulty playing the game. For example I think I ran into a bug where if you died and got reset I would no longer be able to jump with wasd and needed to use the arrow keys.
I didn't really feel "Sonic" from the game. Although it's true that you needed to go fast, you almost always needed to have the spin key pressed down otherwise you would just take damage - maybe that should be the default. I also didn't enjoy the white blood cells - when I was going fast I would not see them and run into them and then get damaged or die. I think it may need more of a warning that they are coming up.
The jump boost was nice but they looked like an enemy so they were easy to miss and it would've been nice if they didn't disappear on touch - I had to wait around for them to respawn. The placement of the blockades and the jump boosts were a bit strange - sometimes the jump boost would require the player to stop and turn directions because the boost would fling the player into a wall. It also would've been nice if the checkpoint had a larger hit box - I missed it a couple times because flinged over it.
I found myself having to stop a lot when the game is about going fast.
I didn't get to the outro but I don't think the intro really resonated with me story-wise. I was a little confused on what was going on - that they were playing cards - and Jackie's attitude was strange. Maybe that was the intention?
One thing to keep in mind is that it would be nice if the title of the game was following the rules a bit more.
Otherwise great job! I think some tweaks here and there could be made but it's a good base to start off with!