I thought the game was very well done, the combination of the graphics and the music really created a unique experience that I can't quite reference to anything else. The mechanics from the momentum based movement, the wall climbing, the sliding, and especially the grappling hook was very well done and I can feel the hours of meticulous testing put behind it.
If I had anything to gripe about it would be that I felt like the game was too "slidy". While the momentum based movement made for a good experience, I felt at times that I was just slipping around and made it harder to do more precise movements.
However, I would like to say that your various applications of the Grappling hook was pretty good and not only added a fun parkour experience, but also added a nice and challenging puzzle factor. Overall, great game!