I like the concept. I'm just not very skilled at games on the computer. I didn't get very far. LOL. The first time I tried jumping to the top and couldn't figure out where the challenge really was. Then I read the page and saw I needed to push the rock. So I tried but got stuck pretty quickly. I tried to let it roll back a bit to try and get it over and I lost the rock.... -_-;;;; I literally couldn't find it at all. Maybe add a button you can click to be sent to the rock, or reset with out admitting "I'm a quitter" for when your rock rolls off to parts unknown.
The avatar looking so weak and only able to jump incorporates the theme well. Great job, judging from other comments I'm sure if my gaming skill were higher I could have gotten further.