If the game freezes, just click inside it (games can get unresponsive if you click elsewhere on the page).
Little ghosts have entered the stage. Help the old sorcerer to remove them by clicking on three or more matching ones of the same colour. Remove six or more at once to get a time bonus. Remove ghosts of the same colour one after another for at least three times to get more magic potions. Use the magic potions on the right to remove or change multiple ghosts.