This is a game of Lines. You need to arrange three or more (four for Expert mode, five for Master) balls of same colour in a row and they will disappear. To move a ball, click on it and then on the destination cell (you must move a ball even if only one is left). Balls can only move through empty cells. If after your move no balls vanish, a few more appear on the board, until all cells are filled. Sure you will not allow this to happen.