The premise is very simple.  There are blocks bouncing around the screen. You have a limited number of shots to remove a set number of them.

Each shot creates an explosion which, if it touches another block, causes that to explode.

This can cause a helpful chain reaction.

One of the many wonderful things about this game is how it pits you against other players.  Rather than posting high scores, it shows you how many other people have reached the level.

Being the massive geek that I am, I've graphed how player levels drop off.  I'm only skilled enough to get to level 89. Must try harder.

What I find fascinating is how steady the player numbers are until each big drop-off. Obviously, at least 50,000 people have downloaded the game, but only 371 players who've made it as far as I have.

Anyway, if you have an Android device, have a play with Prime - it's a great little game.