Not much to say here. I think 6x6 is most appropriate as it gives some degrees of freedom to move without being too large, so as a concept demo this is fine.
I think this level is very good for advanced beginners. It teaches it is sometimes inevitable to think in advance. Step by step. Always THINK AHEAD!
A very clean example! I like that there are no unnecessary blocks, only the blocks needed to show that, in order to not get blocked.