Tap a bubble to burst them before it collide something, what can be easier? But the faster you burst them, the faster you get new bubble on field.
Keep calm and stay on few bubbles, or rush in and show your reaction.
Use your brain to find out which one is most dangerous, or just roll over the phone screen with your face. Hear lounge music and enjoy meditative gameplay, or don't notice anything except smashing the phone with your finger.
P.S. Circles... circles everywhere