Man, this one is tricky! I managed to collect all of the characters... and I feel like I was close to finishing the content you have, but not quite.
The game is difficult for sure, but I found that most of the challenges were conquer able after a few tries. The check points were also spaced pretty fairly I thought.
So, the abilities were all easy, and useful, but the purple/pink characters jump dash combo was the most fun. It was also the most difficult to make use of, since it is by far the most active ability. I think in the long run the jumping challenges towards the end were a bit on the difficult side, which is where I stopped (for now). But I don’t completely hate the challenge... just wasn’t able to withstand it, haha.
The music was awesome! The sound effects were fine. They were probably great as far as matching the gameplay and style, but there were a few that were a bit too loud in my opinion. I guess mostly the switching character effect?
Great job!