Skill system

I am quite new to CreepTD and as such I have no idea how the skill system works. I though I had a few ideas until I played the following game: http://www.creeptd.com/en/games/yxggptfa7ajjuvf9xwk3eq8ufl807tjd where despite holding out fairly well on my own, I lost more skill than my partner who quit right at the start.
So basically, my question is, how is the skill calculated for each game?

Its the Elo-System.
U had the most skill so u get the least points.
For example if u played this game with 1400 skill u would get 0 or 1 points for that game