I've just played World of Goo, the indie title by developer 2D boy that does everything right! The mechanics of World of Goo have more in common with building sand castles then any other computer game and as such is more of a toy then a game. But this is not a bad thing. To be accurate I have to say that I've only just finished the first chapter of the "story campaign" but so far this game does everything right as far as game design is concerned.
It's accessible, simply and easy yet engaging and engrossing. You can jump in to play for a few minutes or play levels of increasing complexity for hours. It's also a feast for the eyes and ears and has a lot of humor.
My only issue with the game is that it's fullscreen, it wants to take up all of my attention while playing. And though this might be most effective and certainly the first choice of most players it's quite odd to play such a light title without the ability to keep IMing on the side. I do that in WoW, why not in WoG?
Watch a video of the gameplay, if you find it even mildly interesting or seemingly fun you'll really enjoy the title. And please, BUY this game. It's cheap, it's indie and it doesn't use DRM. Support a just cause by getting your money's worth.