Pop the bubbles or just watch them float up the screen. (This requires a webcam. ) Press space for an effect that draws the bubbles to the mouse like it's a black hole, then spits them back out going random directions in a ring.
Based on a project by @Scratchteam, and for my local library's Scratch Day event. I made this as an example. I added "glorious Technicolor", bouncing bubbles, and the cool "black hole" effect.