Oh man, i have so much to say about this! First of all, congratulations, fantastic game, i just gave it a 5-start rating on all categories!
Visuals and sound: The art is probably a bit inconsistent. (btw please do NOT look at my game, it is the most inconsistent art you will ever see :D ) While it could probably be improved somehow, it does not at all stand in the way of the fun. Music is nice and fits.
Gameplay: Great, very engaging
UI and progression: Here is where i could imagine an improvement:
Now, balancing this game must have been a nightmare, and you did a fantastic job, it stays challenging while i still have a clear sense of progression. In order not to overpower the player, it is natural that you had to pick very small upgrades like 0.02 to your speed. The problem is that this is not super satisfying for the player, there is no visual clue that you just got an upgrade, and you certainly don't feel it. Same goes for the health stat, since there is no HP indicated.
If you decide to work on this game further (which i believe would be an excellent idea since there is a lot of potential), maybe you could explore the possibility of a skill tree / tech tree. And maybe let the player decide when to enter the tech tree and purchase an upgrade.
Controls: They work well, but mouse control would be nice, too. Also, this game seems super easy to adapt to mobile, i would really consider it! This could be a very nice mobile game.
Sorry for the long comment, but it's rare to find games that are as engaging from the first second to the last! Congratulations!