The tutorial is really nice, as well as the characters. I’m glad you gave the option to skip the dialogue as I had to sit through it for most other games so that’s a great thing to have. Music felt really fitting and it visually looked good.
My first issue was the “J” key to attack, the swing felt really hard to hit, and when I’m going at a high speed and pressing it, more often than not I miss the swing as it basically needs near pixel perfect timing. When failing, it also makes the game extremely frustrating as you lose all momentum and basically have to backtrack and redo it again. And with how slow the momentum is to buildup, it basically meant running, gaining speed, hitting a wall, then having to build up speed again. I definitely feel the attack should be more forgiving, as even at times I hit the blood cell and still get damaged, losing all momentum.
The game is not easy, and it is very common to lose momentum from random walls, to blood cells etc. So I feel a way to “reset” instead of having the player walk back would be good. I do know that you reset to a checkpoint after a few damage taken, but I would rather it be like Geometry dash where you die immediately and go back to the checkpoint without delay. This way, you don’t have to feel like you always have to backtrack after a failed momentum jump. As I’ve been “trapped” in areas a few times, where I have to backtrack all the way to a wall, and move forward at full speed and jump in order to just make it over a wall, as movement speed seems to also affect how high you jump.
For a game that is built around momentum and speed, I feel you did a good job making the player feel good going at high speeds, all that’s left is better level design to let the player keep high speeds for longer. This game has great potential though, and with enough polish, I could see people trying to speedrun it.