# Ratings

The ratings system used in Filler is a variant of the Elo rating system which was invented by Dr Arpad Elo. When a player starts, they have a nominal rating of 1600 points. When a player loses a game, they lose points, and when they win a game, they gain the points the other player lost. In Filler, a player can lose or gain at most 32 points in one game. The number of points gained or lost depends on the difference in the players ratings. A win over a player ranked equal will gain 16 points (half of 32). A win over a player ranked higher will gain more than 16 points, and a win over a player ranked lower will gain fewer than 16 points.

The Filler rating system assumes that a player will never be able to defeat a player ranked 400 points or more higher. Consequently, defeating a player ranked 400 points lower will result in no points being transferred. Defeating a player ranked 400 points higher will result in a full gain of 32 points.

For the first 20 games a player plays, their rating is considered to be provisional. This means that wins over higher ranked opponents will gain them bonus points, and losses to lower ranked opponents will cost them penalty points. This allows a player to reach their approximately correct ranking faster than the usual system would allow. The bonus and penalty points do not affect the opponent's rating.

The benefit of the rating system for players of Filler is that it allows them to match their skills against the robot players, and to easily choose robot players with sufficiently challenging skills.

The game keeps track of rankings, which are your categorisation into skill levels according to your rating, and head to head results, which are the historical number of wins and losses for each pair of players. See also Rankings.

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