Hi guys! For level 30, the best way that I've found is to clear the bubbles in the center first, then get to the left side bubbles, try to shoot as careful as possible.
Here's a trick you guys!
When ever you wanna let a bubble bounce to the wall, it will shows two dots of the way that bubble will go when it bounces. (as shown in my picture),
According to that two dots, you can stare more accurate without using the "long line" boost!