: Who knows how the algorithm actually works, though. For instance, Halo 3's
: rankings used truskill, but it was a sort of screwed-up truskill which
: behaved like a progression system when you hadn't played very many games.

Playlists like Action Sack, the ranking is based on individual scores gotten during the game, whereas I believe Castle and others are based on the teams overall score and if they win/lose. If that makes sense.