Finished up tonight. Very cool game. When you have all the movement abilities, some of the levels feel like a puzzle as you slice through enemies at breakneck speed to maintain momentum without ever touching the ground. The bosses are fantastic; some of the best in any 2D action platformer I've ever played. I really enjoyed the throwback style of the final boss as well.
Younger me would have jumped right back into hard mode, but current me will call it good and move on to the next game.
EDIT: Apparently there is no hard mode? But judging by the fact it says "Mode: Normal" on the continue screen, hard mode is probably coming at some point.