The window size option is a thing that is necessary in almost every single game in this jam, so kudos for adding such a nice feature! Although, the maximum re-scaling still isn't enough (at least for my screen, I don't know if screen size affects it).
It's a simple concept, similar to the classic Shoot Em' Ups, but it's fun and it works the way it's intended to :) It also feels like a Gameboy game due to the way it looks, plays and sounds.
Great job! :)