Look here: http://gowentgone.de/master
This is a pretty simple version of the famous Mastermind game.
Rules are simple (as the name suggests). On refresh (or reload) of the page, the browser chooses four colors (the “code”). Duplicate colors are allowed. Worst case is that all four colors are the same. The “code” is hidden but can be revealed manually.
You start in row 1 to choose four colors. You do that with the mouse wheel while the mouse cursor is hovering above one of the big dots, then hit [play] (both buttons behave the same).
In the result column it shows you with a white dot the number of colors you chose correctly but put them in the wrong place. The number of black dots shows the number of colors you chose right AND put in the right place.
More info on Wikipedia.