Hey WoN! Glad you liked the demo overall! :D
About the UI, if that's about the scrolling resolution panel you are talking about, well it's not a bug that moving the mouse cursor makes the panel scroll (that's what I understood as the UI bug from what you told me on Instagram at least). It is an intended behavior.
The game is meant to be hard but offers a lot of checkpoints like in Celeste so you can try again quickly when you die!
I think when you say boost jump, you are talking about bouncing on the floor, right? You can complete the whole demo without bouncing on the floor at all, I designed it that way. Bouncing on the floor is only mandatory to get some optional pieces in the level! The only exception are two switches on the floor where you need to use the floorbounce to activate them. All platforming sections can be done without floorbounce.
I don't plan to have a ghost to explain but I'll teach it in a different way in the final game. This demo is tight and doesn't allow too much time to explain the controls. I will have 2 tutorial levels at the beginning of the final game: one for the dash and the other one for the bounce.