Incredible atmosphere (having some echoey SFX would have elevated it even further, but I couldn't hear any sound other than the somewhat creepy music). The combination of the surreal fridge hole, the music, the lighting, and the setting of being in a well all work together so well -- very cool. (Also, there were trampolines, but they seemed absolutely useless at bouncing me, so I never used them for anything.)
I also liked the unorthodox tools; the knockback of the punching doubling as a way to get up a little higher was very cool, and the shark plank launcher situation was inspired.
I had some issues with the controls. First off, the jump felt a little too floaty, so I had some issues with landing where I intended to. (More on issues with landing on things later.)
I don't know if this is just me, but I had some weird issues with the mouse -- it felt a bit jerky, like it lost input every now and again, making it hard to make smooth turns. Ultimately it was fine, because it wasn't crucial to face in a precise direction. (My mouse seems fine outside the game, but it may still be a hardware issue on my end.)
Okay. The planks.
I really like the concept, and it opened up some possibilities that were interesting. However, I got unreasonably frustrated with the execution. It feels like the planks disappear WAY too fast. The sign says they last 60 seconds, but in reality they last only 6 (or 5), and disappear with no warning. This means you have very little time to aim your jump, land on the plank (which sometimes takes longer than you think because of the floaty jump), shoot a second plank, and aim and jump to that plank. It's doable, but feels very tight. (Part of this is the inherent difficulty of precision jumping in a first person game, so maybe just a skill issue on my end.)
If the planks were a bit wider and easier to land on, maybe this would be less of a problem, because slipping off the sides was a full-time job for me towards the end.
I (eventually) made it out to the top, and was met with more surreal stuff. Incredible.
Good overall experience with some frustrating bits (which may be the intended experience). Nice!