Really really wonderful game, I felt like playing on a ps2. There were some parts that I got stuck, but thankfully there's a full walkthrough video, I wasn't aware of the importance of the collectable gems, but recollecting them a second time wasn't much of a trouble. And finally I got to the credits room.
There are some elements that I forgot and/or missed during my run, and playing the game with walkthrough video on my side isn't my thing. Since jumping and high-jump are ones of the focus of the game, it should allow Holding jump input for easier continuous jump(I know that there's a jump anticipation feature), and there should be tutorial and reminders about high-jump at a place where the player potentially need(there's an Only high-jump reminder placed in a LATE game section).
Overall, a very polished game, I see so much hard work put into this, a near perfect piece of art.