This was very fun to play. I was skilled enough to use both characters until the hard mode humbled me haha. You have the colorful art, the music, and the gameplay all coming together to make this a great experience. I do hope that you continue to work on this and see where it goes.
If I had to give any feedback, I'd probably just say have an option for 1 or 2 players. This is just under the assumption that the player wasn't meant to control both at the same time. Felt bad when I perfectly completed a stage with one character and saw my score plummet from not using the other.