Come2Play
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Player Ratings

Come2Play's rating is based on the Elo rating, which is common in classic chess and online games (http://en.wikipedia.org/wiki/Elo_rating_system).

Players are rated for each game, so a player will have a different ratings for SpeedChess and normal Chess.

There are two kinds of players: new players and veteran players.Both kinds have ratings, but a new player cannot affect the rating of a veteran player, and when two new players play, their ratings do not change.

For example, suppose players V1 and V2 are veterans, and players N1 and N2 are new. When players N1 and N2 play, then the ratings do NOT change. When players V1 and V2 play, then the ratings do change. When players N1 and V1 play, then only the ratings of player N1 change.

How to become a veteran player:

1. You must be a registered user and have verified your email
2. You must have been registered for at least one day
3. You must have won (a normal victory, not due to a timeout, opponent disconnected, or opponent deciding to lose) against five distinct veteran players
   

The rating starts at 1,500. This is the scale:

2400 & above Senior Master
2200 - 2399 Master
2000 - 2199 Expert
1800 - 1999 Class A
1600 - 1799 Class B
1400 - 1599 Class C
1200 - 1399 Class D
1000 - 1199 Class E

This is the formula that updates the rating:

Suppose players A and B play against each other.

* The rating of A is RA, and the rating of B is RB.
* SA is the outcome of the match:
SA=1 means that A won,

SA=0.5 means that the game ended in tie,
SA=0 means that A lost.
* K is 32 if A is a new player, or 16 if A is veteran

The new rating of A will be:

max(1000, RA + K * (SA - 1 / ( 1 + 10^((RB - RA)/400) ) ) )

"max" ensures that the rating cannot go below 1000.