One of the things that I noticed at gamification world congress this year, was a few people mentioning Flow in their talks. As most of my readers know by now, I love the idea of Flow, not just as a pure idea of “in the moment balance and being in the zone” but as a guide to how we should design experiences. The logic of keeping the difficulty of challenges in line with the users relative skill is faultless in my mind.
In game design and gamification design we are also used to the idea that you “zig-zag” the users skill with the challenge levels to keep users engaged and in the Flow “zone”.