Art is really cool but there is one issue for me: the character's projectile don't fit well with the overall art style.
Another thing I noticed is that the boss is too tanky, I've found the fight to be too repetitive because it was too long.
Enemies don't stand out from the background, probably for the chosen color or because the background is too noisy.
That being said, I love the mc and the shopkeeper design, he sells so much stuffs! Enemies are cool. The gameplay loop is solid.
Great job!