The ending is the best part which increases my rating considerably.
The rest of the game… well…
Just one thing – the blue blast has a different colour than 'blue' you and it's annoying because initially, I thought you're supposed to mix 'cyan' from blue and green. That can be an idea for a game mechanic if you wish to expand the game. Or just fix the fireball.
Although, I do feel like 'adding improvements' wouldn't fit with the overall spirit of the game…