The purple shots are too hard to see.
I'm not sure how this is different from nuclear throne. You even used a similar font, font wiggling, player shot and cloud effect, from the looks of it.
I get that placeholder art can be useful for finishing a prototype, but a bunch of rectangles with letters would've been a better choice. The small window doesn't hide the fact that your guns are a plus sign, a child and a treasure chest. Also, your sprites seem to have a level of anti-aliasing not present in your tiles. That's not good.