Your game is fun. The drawings have a really cool unique charm :D i can set my own difficulty/balancing pretty much which is actually quite ingenious system imo. i think your idea has so much potential and is a super creative way to balance the game. i think that masksystem would cater to a wide audience. it could be the hardest pain to beat the boss or the biggest steamroll easymode and everything in between, so something for everyone.
i would have loved to see some more negative runes, because the boss mechanics are a bit too easy for me even without any runes, even 5x juggernaut felt a bit too easy.
but i understand the time constraints and you already mentioned you had no time left for complex boss patterns.
For such a short time you made a really cool game, nothing felt off in the game other than it beeing a bit too easy for me.
Great Job :D !