Nice, I remember a previous version of this.
introducing the player to one element at a time is good to encourage experimentation so that was a good decision.
I saw that there's upgrades for player speed but the base speed is atrocious, I spent the whole game with either the shadow-water dash or the water-fire dash combos just because it was much faster.
Arena nodes didn't do anything.
Changing your selected elements is a bit clunky, it would be easier to combo different spells if it were faster.