Most of the challenges are not too hard. There were a couple levels where I gave up on trying to figure out what the level designer had intended, and used the capabilities of the language to create my own object types like "bridge" instead of implementing "jump" code. But that's the beauty of a programming-language based game, there is (and ought to be) more than one way to do it. Similarly, in some of the AI levels it was easier to code "follow what my player does" rather than script the robot to do what I wanted.
The game uses Gist to store your solutions to share with others, if you want. (Other people's solutions don't seem to show up in search--- not sure exactly what's going on, is "anonymous but private" really a valid Gist state?)