One hears a sound and, at the same time, there is animation.  You must click on the ball which was animated.  If the correct ball is selected, a nice sound is heard.  Then there is a sequence of two sounds.  You must click  on each of the two balls, in the right order.  This goes on, with the sequence getting longer every time.   


Every time the wrong ball is clicked, a nasty sound is produced and the left hand cylinder fills up.   After ten mistakes, the game is over.  After a mistake, you must continue until you find the right ball : there is no new sequence given before the last one is completed. 


The number which shows up in the lower window is the number of sounds in the sequence.