Super cool demo! Fixed a lot of my gripes with the climbing in Hatch, while delivering more of my favourite parts of Hatch - the section near the summit with all of the long jumps onto thin platforms that have you biting your nails - here delivered with way more crunch and weight to them.
I also think this makes a really cool speed game, as trying to go as fast as possible leads to more daring leaps and in some sections a great sense of flow when you're jumping between platforms and slopes at top speeds. That said, the sections where you have to climb directly upwards break this flow, as suddenly you're just holding up for a while without doing anything (it's worth noting that in the first playthrough of a level, when I'm not playing for time, this is totally fine, I'm slowly looking around at the environment and planning carefully and so the slow pacing of climbing directly upwards feels right). I wonder this could be addressed by making jumping and regrabbing equally as stamina-efficient as normal climbing, so that if you're going for speed you have that option which is a) slightly faster b) slightly more dangerous and c) means you're still actively doing something
I also think it would feel nice if stamina instantly recharged when you touched flat ground rather than having to wait for it. It feels realistic to need to wait for your stamina, but again it breaks that flow when you're trying to go fast. It also discourages leaping towards platforms at the end of a climb (because it uses more stamina so you have to wait longer) which is a shame because doing that feels really fun. The slow stamina recharge could still be used when sliding on slopes though because then you have the fun tension of not being sure if you'll get enough stamina back or not.
One other minor gripe was that not pushing off when looking below the waist and jumping from a wall feels unintuitive to me. I feel like I should be propelled forward in the direction I'm looking when I press space (maybe not if I'm looking directly down though), and maybe dropping should be a different key like control or pressing left-click again. This could even lead to the slightly interesting decision between jumping down propels you so is slightly faster, but uses more stamina, whereas dropping is free.
Backseat game-designing aside, this was a really fun demo that shows a lot of promise, and I'm definitely going to wishlist the full game on steam.
p.s. I saw in the trailer that there looked to be some sort of grappling hook mechanic, which I'm very excited for. Grappling / swinging mechanics make literally every game better :)