Continue to train the brain. Added competition

Six months ago I wrote a post about my interest in exercise for brain training, which was a small site with this kind of exercises established for all those wishing to embark on the path of cognitive enlightenment. Since the site was done with an eye on desktop games and apps, and it turned out in fact that app only on the web. But recently it was decided to correct this little flaw and add some interaction between users of the website, in the hope that someone will be able to give additional motivation to trenirovkam. The first thing that comes to mind is of course competition.

Horizontal separation

First, there were attempts to find a third party service who would be quick to tie, but all I found was sharpened by a casual game with a simple single table of results and achievements pinch. I would like to out of the box was the separation of users by their skills(fairly standard practice, for example in games like LoL and SC2), because if there are a hundred people, then obviously someone will be to the hundredth place, and perhaps will feel not very comfortable looking at the top ten results at times more than him. Therefore we need a mechanism for splitting into smaller groups of equal strength. In the end had to write it himself.
I was not too philosophize and try to discover what ingenious algorithms for this task. Time should be split into homogeneous groups, then we get the standard task of cluster analysis, we take the k-means algorithm and get the split. The only problem that arises is that too good and too bad unable to grab the whole group. As we go from simple and consigning that task to a known issue in statistics, the problem of outlier detection, we take a simple algorithm for finding them, and before using clustering intercept the results and automatically credited respectively in the best and worst group.
Overall, we have a horizontal split. It would then be possible to improve the system by adding another and a vertical split, which would have solved the problem of too many of the same results. That is, instead of having one group with the results 1 1 1 2 2 2 3 3 3, it is better that there were three equal groups 1 2 3, 1 2 3, 1 2 3. But as participants is not very much, and the problem is not so acute, it was decided this upgrade to be postponed until better times.

Format

Static list from the top, it seemed to me less interesting than the permanent live, so I selected the format of the weekly competitions. So how does exercise bring the greatest benefit when their regularity, it would be nice as it is to stimulate man that he would and the next day went to the site and made an attempt, so it was decided to upgrade the position and the League once a day.

Total came out so that's not a tricky system. Take part and leave feedbacks.
ru.brainexer.com/contests.html
www.brainexer.com/contests.html

Article based on information from habrahabr.ru