Not the op, but it had great docs including links to interesting papers, referenced real world problems (git, cryptocurrencies, consensus), had a set of levels organised around the theme of consensus nicely graded from easy to quite hard, and was doable in about a day of solid effort. Even if you didn't complete it probably felt like a learning experience for most people. Also, it was fun. Finally, the meetup afterward run by Greg explaining their architecture and issues encountered was interesting.