I love this idea! Honestly, I had a really hard time with the controls and actually had to reload the game to figure out how I was supposed to move up. Once I got moving I felt like holding the key was doing the opposite of what I expected it to do. I think this would be more fun with a tutorial section that kept the instructions on screen in the background so the player has time to process how to move. Or at least keeps them on the screen a bit longer while the player is experimenting. That being said I loved the snow mountain aesthetic and your low poly character! Great work. :) 

I actually really enjoy the climbing mechanics even though I a really bad at it :D

The beginning could be a bit easier. From your screenshot I take that there are checkpoints or comparable. You could make it so the difficulty increases but perhaps that is just the rookie in me speaking :)