ELO

Its very similar to dota 2 MMR except it uses your entire match history.

Basically it is based on a "prior" that your chance of winning a game depends on skill difference, so you get elo for winning and lose it for losing. the amount depends on skill rating difference at start of the match.

uszanowanko

There is no ELO in Zero-K.

No it wasn't. It's called Whole Histry Rating so it takes your whole game history and makes rating out of it. Thats why people who haven't played in a long time have rating reflective of their winrate against players back then (that would change pretty quickly if they were to play again though).

So say a dude had 60% winrate against me 4 years back. That means (if he hasn't played with any other people) the system thinks that he is a better player than me and his WHR will reflect that. As such WHR adjusts constantly (even retroactively) and ELO only adjusts at the end of the game.

quote: May I ask why Casual has WHR?

To have a ladder (http://zero-k.info/Ladders) you need a ranking. Also to have a balanced casual game you also need a ranking (except you do random teams).