Extremely well done and beautiful! I don't know what PICO-8 is but good job using it! I really enjoyed my expierence with this game. I like the concept (it was similar to mine with constantly changing powers, but yours done much better) and everything felt very polished. Graphics and soundtrack were very well done.
Unfortatnely the main bug was annoying, since you mentioned we had to restart the game if we die, and I believe that puts us all the way back to the beginning (unless I missed a save function?) After the second death I wasn't too interested in repeating the first 5 minutes again with basic powers.
The one thing gameplay wise I didn't love is how whenever you get hurt your ability automatically changed. It seems like some areas, especially where you get the ability, are made for just one or two abilities. But if I got hurt it would then change to something no where near as useful.
Otherwise though amazing game and followsthe theme very well! Defintiely could be a full indie game!