That single click triggers a chain reaction; circles start exploding, and other circles colliding with the shockwaves explode as well, creating their own shockwaves, which then catch other circles.
It's been done before, yes, but this one is a great iteration. The soundtrack is mellow, with lots of piano and some nice percussion (not electronic - it sounds like drums).
At each level you need to make a certain number of circles explode to go on to the next level. I got up to level 12, where you get 60 circles and need to make 55 of them explode. And then I kept trying and trying, but simply couldn't get it. I did get to 54 circles a couple of times, but as they say, you don't get points for trying.
There's no time limit, so you can carefully study the pattern of motion and place your click at the exact right place to create the best chain reaction. I've found that clicking near the middle of the screen works quite well, especially if the balls are slowly moving in that direction. By the time the first shockwave dies off, the oncoming balls usually hit it and the chain reaction continues.
What level did you reach? Screenshots please!