Cool game! I liked the mechanics, I thought the 'less party members = more damage' was a nice twist on the 'less health = more damage' route many people, myself included took. The art was fun and very unique. I enjoyed all of the different attack animations on the heroes.
If you wanted to improve, I suggest fixing the GUI scaling, my screen is large so I was able to see all of the menus, even when they were not suppose to be on screen. I could also see around the fade to white and fade to black boxes. The gameplay also got very repetitive and had no sense of progression. Making waves of enemies with a shop in-between or even a high score would be cool. Lastly, health bars on the enemies could help to make the gameplay more informed, I could never tell what enemy was lower on health to focus on.