Thanks for playing and thanks for the honest feedback.
I actually had more plans for the HUD; I wanted to flash the bar when you got hit, and I was considering flashing the screen as well, but I ran out of time and energy to actually implement it. There definitely is a lack of feedback there and I wish I'd been able to do more.
Shift+move is a power dash which sends you flying along the ground, shift+space is a power jump that shoots you upwards. It's finicky as all hell but I never figured out something better, and I kinda got comfortable with it because you do get used to it if you play the game over and over and over again for a week which I did for testing.
I talk about why this ended up so weird in my postmortem so you can give that a read if you're curious.