Oh and on the upper right corner you can see how many balls you have left. Pop all of them and you'll proceed to next level. On the left side of the bubble bar there's a limit. If there's more bubbles than what the limit says, it's game over. Rate both of these comments so people will know better. :P
The gray balls next to your score are kinda like your lives. When you shoot a ball and can't make a group of at least 3 of the same color, you will lose one of them. When you've lost all of them, a new group of balls will come. Try to play slowly because sometimes when you shoot 2 balls in a row, you will lose 1 gray ball even if you succeeded to blow up some balls with both of them. Let the balls settle down before shooting new balls! This way the game can be very enjoyable. I'm giving it 4/5.