This is very well done! I really like how distinct the characters are in terms of gameplay. The pixel art is very good and gameplay is overall fun. I also really like the end score screen. I wanted to add something like that to my game but I didn't have the time and have a hard time with UI.
The only thing I found that could be improved is the boss fight at the end. I was having trouble with him at first, but eventually discovered I could just sit in the lower left corner without any of his attacks hitting me, while I shoot away at him. Overall great game and good luck with future development!