World of Goo pits you with the goal of getting your little goo droplets from here to there in a 'bridge building' manner. In essence you'll be dragging droplets to new spots on the screen and a pair of lines will follow you to show the connection you're about to build. Move too far away and you won't be able to make the connection. As the name of the game states, you are building with a somewhat flexible goo substance so don't expect rock hard connections, but rather connections that flop back and forth as you work to build up and across to the giant pipe in the sky.
Graphically the game is good and the audio is nicely integrated to make for a smooth game play experience. The touch controls work well with the occasionally irritation of too many little goo balls being too close together so it can be hard to single out just one when there are different types of balls in later levels... a minor irritation. Likewise, an errant tap here or there can result in a connection being deleting and your whole structure tumbling back to the ground. Be careful out there! The neat thing about this game is the variety present in the many levels meaning that each level is typically a leap and bound beyond the previous one offering up a new challenge versus being another variant on a theme. This game keeps you guessing and thinking...
In addition to the many levels the game includes which are divided amongst several nicely themed chapters there's also an ongoing competition to build the tallest tower although that might not be obvious at first. As you play the game you'll have a goal of saving a number of goo drops and often you'll exceed that goal. Each of those extra droplets goes to your 'goo bank' which you can use in an effort to build the tallest structure which is ranked on a global leader board.
As stated in the first paragraph, this is a great, great game! It's premium priced at $5, but that price is fully justified, but it gets better... they even have a free demo containing the first chapter's worth of levels to get you started before you plunk down your cash. There's no reason not to try it... and then buy it. 5/5 stars.