Great, but misses some things.
You did a very good job on this game (especially the graphics are stunning), but i think you miss a few things and made a tiny mistake.
First the mistake:
Creating a dash function by double tapping your walking keys is, in this case, a bad idea. The dash function will prohibit you from going in other directions for a short time and you won't be able to jump if you did your dash on ground. Dashing by double tapping will undoubtedly create a lot of accidental dashes and that's not very handy because of the side-effects. You can solve this by giving it a key for itself, like in the robot unicorn attack game.
The things you miss:
1. A detailed stats page where you can see for how long you have played, how many enemies you killed, what your biggest combo is, how many levels you completed, how many times you died, etc.... This always is fun to see and keep track of.
2. A page in which you get to the more advanced game mechanics. Not only telling you that
you can die by sideways bumping a rock or
that you cannot jump while dashing, or
that you not only get an extra life on your 3combo, but also your 6combo, 9combo, etc. etc.
You should also say that you won't get +100 pts per creep for every extra combo, but that it scales. (after your 10th combo (1000 pts), your eleventh combo will not be 1100 pts, but 1200, and after your 15th (2000) your 16th will be 2300 i believe.)
And that if you dash at an enemy in mid-air you will make an extra jump, but not on the boss.
And probably more and more things.
3. You need more variation in your boss. Even changing the hue every world would've been much better.