I like the dash mechanic. It feels good to use and works well. It's exhilarating to zip around and through gaps.
The level design could use a bit more thought though. It felt too claustrophobic. The last level is the biggest offender of this. I wanted to dash around and move quickly but found it better and easier to just walk around when the walls and spaces were so tight. I think the game could be improved by focusing more on making the dash an exploration mechanic and instead having wider areas that also have platforming challenges. An example of this would be to have coins hidden in the air that can only be reached and found by exploring high up or in areas only reachable through dashing. Something good though in its current design is giving windows for the player to see through spaces. This gives the player some direction on if there might be a coin nearby and which direction to start looking for it.
The controls could also use some work. I played on controller and the jump button doesn't feel very natural for me. This is of course a personal preference, so feel free to take it with a grain of salt. I think the keyboard controls could be improved by setting dash to mouse controls rather than shift+wasd.
Good job overall!