I thought this was a fun game! I liked the controls, overall moving around felt good. I felt like I was super-smart when I discovered the climbing mechanic without seeing the instructions.
I didn't like that I had to use trial and error to progress - checkpoints and making it possible to see what's coming by using the climbing ability would have made me feel like I was "mastering" the game (e.g. I kept trying to slide down and climb to look at what was further down, but still couldn't see the next obstacle.
Overall I think you did a great job with this game, I had fun playing it and that's what matters!