Arena Elo

Everyone starts at 1500. An Arena lobby is scored as a round robin: your team's rating is the average of its players, your expected result is your average win chance against every other team, and your actual result is the share of teams you finished ahead of (1st = 100%, last = 0%). Every player on the team gains or loses K × (actual − expected) with K = 64 — so winning an even lobby is about +32 and finishing last about −32, while beating stronger lobbies pays more. A player's first 10 games move 1.5× as fast and are marked provisional.