Nice take on the theme, and really enjoyed how coherent and bright all the design work was!
I'd pad out the sound a little more to give it a stronger atmosphere; the street for example would be great with a light-hearted song which then turns into something more action-heavy when you go to fight the invaders.
It also could be cool to have the narrative setup have within the game - say you walk around the town and meet people who give you the information from those screens. I say that because, at least for me, I find it quite draining to read a lot before starting to play... but maybe that's just my short attention span... haha
Great job, especially for your first jam!!