From the game description:
Set in stunning 3D environment, your job will be to throw Bubble Blast at enemies and push them into the surroundings water. Be aware that the enemies are smart and have protected themselves in such a way you could lose Bubble Blast friends if you are not careful enough.
Here's a walkthrough, as I played right through the 20 or so demo levels:
Starting with an animated intro, all rendered in real time in the same style as the game itself - you'll get the idea - evil red blocks that need to be knocked into the sea and a plucky green hero to be rescued....
Angry Birds-style cut-scene-hints show what to do when anything new is introduced...
Gradually more and more complexity is introduced, with barriers (barrels, trees) and with the crates balanced precariously. You can swipe around the scene in 3D, so as to be able to fire from any angle - happily targetting is precise, just tap where you want to 'hit'.
Light effects, sometimes having to fire 'into the sun' are something we don't see often done this well in mobile games....
The levels based on ice are tough - as you might expect, once knocked, things keep sliding for a while - the semi-transparent blocks are glass, by the way - these shatter when fired on.
Of special note is that the physics here is impeccable, with some rescues involving firing multiple bubbles quickly in order to catch a block as it rocks after an impact, in order to knock it further. Great fun!
You can download the game freely here, to get playing. You get 20 levels for free and then there's an In-App-Purchase of £1.49 to buy the full set of 300 levels, which seems perfectly fair and proper. And the purchase happens through the Store, so can be re-applied on future devices or after re-installations.