Click on start and enter a name if desired (if you do, your score will be saved automatically after each completed level).
Each level consists of a number of marbles connected by strings. To complete a level, you have to drag & drop the marbles around in such a way, that the strings don't cross each other (changes its color to green). The faster you are, the higher your score.
Want an even higher score? If you fulfill an achievement in a level, your scoregain for that level is far higher!