Yeah the control was a bit annoying when you have to hold down before it starts going again (I assume this is in JS and you're just checking "keydown"? (You have to keep track of up and down yourself rather than only checking that event directly, because it behaves like you're typing and that's not ideal).
Would have been nice to know my level progress to know how far I had gotten.
It's a solid game though. Very easy to learn and play and the difficulty ramp and new challenges is well balanced. Nice job!