Thanks for the great review. You mention many important points. Yeah we focussed on game play over graphics. But sadly the music/sounds were a last minute addition so they might not have turned out that good.
Some tutorial for controls would have been necessary, and reading your text I'm not even sure if we properly communicated that the player is invincible while dashing. Powerups and different weapons were planned from the beginning, but cut due to time constraints and I wasn't sure how/when they should drop, but you gave me an idea how to integrate them, without the enemies randomly dropping them.
Tuning the difficulty is always difficult, because I usually played the game already hundreds of times until it's finished, so I just included multiple difficulties (with a third one, that only even unlocks after you beat it on "Hard"), but I think I could have done more, like allowing the player to retry directly at the boss they died at instead of the beginning, at least on lower difficulty settings. But I thought it isn't a big issues since the game is rather short with 3 stages and can approximately be played through in ~7min (in a single run).
Ok, this turned out longer than expected. To conclude: thanks again for the helpful review.