I agree, the ability to hold the button down for straight extended travel should be mentioned early, because I had no idea until about level 11 when I finally saw short lines behind me as I clicked. I also really wish I'd known early on that tiny mode is best for precision movement--those laser-barrier levels would have been much less frustrating.
Also, level 15 boss is unplayably difficult. You didn't have to make bosses able to see tiny mode; just make it so tiny can't do damage to them. And the turrets on the ceiling! And the picky-as-shit timing on combo length, I can't get anything started. Also what's the deal with the sign saying 5-combo makes you glow or somesuch? No idea what that means, and I wasn't able to discern a meaningful difference.
All in all I had no idea what I was expected to do or how to do things most of the time when I played this game. There's neat stuff in here, but the bosses are completely awful experiences and the general control literacy is low.