Drag back from the red ball and let go to launch it like a slingshot into the bubbles.
Level 1 has 1 bubble, level 2 has 2, and so on, forever — clear the screen to advance. Hold the ball against any wall for a second to relaunch it; from level 2 on, it splits into extra balls (up to 10) that scatter into play. Grab one while it's airborne to keep it for good — but a real split takes real recharge time, so it's a periodic power move, not a free repeatable clear.
Not every bubble is simple: Heavy bubbles take a few solid hits to crack and drain your ball's speed when they do, Bouncy ones dodge around and ricochet your shot off hard, and Bomb bubbles detonate on pop, chain-popping anything nearby in a shockwave. Ordinary bubbles float forever until popped — except big ones, which shatter into a swarm if left too long (watch for the red pulse).
Every 4th level is a Core Breach: pop the golden core(s) hidden behind rings of indestructible shields by banking your shots around them. Let the screen fill up and it's game over.
The bubbles filled the screen.