This was a pretty good time overall! I liked the character designs you came up with, and their powerups also very nice. My favourite was the magnet one, I think it was the most unique of the bunch.
I also liked the idea of having boss fights all about auto attacks and dodging, with the characters adding new abilities to be used. If you can add some depth to how and when to use those extra habilities i think it can really make those sections shine! (as it is now, it kinda feels it's all about mashing all the habilities i could)
I like the sort of NES aesthetic you went with, I think it looks good, tho the animations could use a bit of work, running looks a bit awkward, especially with the purple character(I think since she had no running frame, she was supposed to be a sort of floating when running type of character?).
Music changing according to the character you are using was also a good idea. The main critique here is maybe instead of always changing the whole track on, maybe it could just be a slight variation to the music(like always the same song but purple character as more drums on it, yellow character as an electric guitar, magnet synth etc.). Another thing you could do is like everytime you unlock a new character, make the track change to another song.
The map being a big level can work, but as it is now i think it needs a bit more visual variation to make it easier to traverse, as it is now, most of the time I was kinda lost. You could also add a map to ease this feeling.
Overall i think this was good and it has potential to be a gem, good job! :)