I think you have something cooking here, but there just seem to be a lot of design oversights everywhere.
Like the starting velocity from a standstill is just PAINFULLY too slow, especially when you're trying to collect the whatsamacallits and you're forced to do tight turns a lot, which just kills all of your momentum. Likewise, the natural stopping speed ramps down way too slow. This is not that good considering combat.
Also I dont know if I just missed it somehow, but I dont think the tutorial ever tells you HOW to glide, it just tells you to do everything else for aerial movement before gliding.
Also, I think it might be an engine optimization issue, but it really feels like the game is fighting against my mouse controls trying to look around. Like there's a very clear jerking back whenever you're trying to look in any direction other than where the character is facing.
Also a weird issue I came across after the first actual level. When you finish the level, it acts as if the game had restarted and throws you into the logo that you need to click to get to the main menu. No fanfare, no 'Level Clear!' no nothing, just welcome to the menu again.
I think considering all of the above, calling this a demo is a bit misleading. A WIP PoC maybe, but a demo is usually a part of a already completed work, a demonstration piece, and this really doesnt seem finished or polished in any direction.