I like platformers and I like grappling hooks, so this was a really nice entry.
One thing I really liked was the emphasis on the camera movement on certain actions. It has this dynamic, "not-stiff" feeling to it.
Going for 3D always seems risky to me, but that stage transition was absolutely worth it.
Nitpicky stuff: the player movement is a little floaty, so some jumps were really tight. Also, the mouse was not "captured" by the game, so I sometimes hit the RMB on my desktop which caused some failures... (played it on Linux, if that matters).
Really nice entry. Thank you!