I really enjoyed how the game transforms with the upgrades, and it's quite fun to explore the new possibilities (breaking blocks, changing gravity). I only read the description after playing, and it was interesting to see it all become a boss arena while I was playing.
I think the only thing I have to add is that the final fight is quite difficult; I feel it's more because the speed of executing the gravity-altering command makes it hard to synchronize with the need to dodge.
Very cool idea! Mechanics that fit well, good art (especially the final boss, very good).
Congratulations for the game :)