Hi there!
I just finished playing the demo, and I do have some concerns with the player jump. There is a gap on stage 1-12 that is just too wide to consistently jump across. I do understand that the longer you hold the jump button the higher the jump the player gets, but it does not feel consistent with jumps that are that wide in previous screens. If the distance traveled was just slightly smaller, then the jump would not feel as difficult to make.