Really fun game! I included it in my compilation video series of all of the GBJam 5 games, if you'd like to take a look :)

i already built an alternative way to control it. I will upload it after the rating period ends :)

Nice job! It's a nice and simple game, and the help screen is informative. The A, B and Shift control sceme forces my hand into a very unnatural position, so please look into providing an alternative. Also, a bit of spicing up in the enemy types wouldn't hurt to keep things interesting.