I like the music and the character but it's just so difficult to play normally. Sometimes the jump just doesn't work and the double jump is too. I ran into some invisible walls. However, I do like how tight the controls are!
I'm not sure if it was on purpose or not but it looks like you're not able to jump in the alt world but I was able to finagle a way to jump in it. It made finishing the levels very easy when I did haha.