The game principal is well known: Behind a cover there is a secret code consisting of four colors. To find it you need a little bit luck and good combination skills.
By multiple clicking with the mouse you set four colored token in the first row. When you have finished the row and submitted it, the first trial will be rated: For every correctly set color you get a black pin, for every right color on the wrong position you get a white one.
So you know, how many correct colors you've found, but not which colors and on which position! By trying and combining using the rating you can resolve the code.