At the end of every game, players who are not defeated are awarded a score equal to the total number of Grass and Forest tiles on the map. The total number of Grass and Forest tiles at the start of every game is 100.
This score affects a player's rating points. Players start without any rating points and can never have less than 0 rating points or more than 100. After every game where a player obtains a score higher than their rating, their rating increases with 10% of the difference rounded down to the nearest 0.1, but at least 0.1. If they obtain a score lower than their rating, their rating increases by 0.1.
If a player loses, they lose 10% of their rating.
For games involving only one human player, the rating increase and decrease percentages are 1% instead of 10%. For free-for-all games involving at least two human players, the rating increase percentage is 1% per human player and the rating decrease percentage is 1%. While a player's rating is below 10, the rating increase percentage is at least a minimum percentage; this minimum scales from 10% at a rating of 0 through 5% at a rating of 5 down to 1% at a rating of 10.