I found it quite difficuly to pass levels 1 and 2 just with the use of A/D and Space to jump, without the use of the right click to dash, I sorta just figured it our for myself that I could use it to dash around, defeat enemies and projectiles and that it resets on a kill so I can chain link them together. If I remember it was only introduced in level 3, but I needed it much before that. Overall I still really like the game, and found the dash attacks when chaining them from one enemy to another really satisfying.