I think this thread should make it:

https://bitcointalk.org/index.php?topic=922898.0


It was the first time a multiplayer game was made properly provably fair, and introduced the idea of committing to a  hashchain which will get seeded by a (bitcoin) blockhash that has no yet been mined.

And since that time, it's now become somewhat of a standard being used dozens of times -- frequently on bitcointalk.