This is an awesome little puzzle game. The basic goal of each level is to use your living goo balls to construct physics based objects in order to accomplish different goals.
The best way to describe World of Goo is charming. The graphics are simplistic but have a distinct art style that makes them very appealing. In addition the game is infused with cutesy sound and visual effects that help develop an attachment with the world.
The puzzles themselves are generally of a physics based variety and the design is simple enough to pick up quickly. Like the best puzzle and strategy games, however, while the learning curve is fairly small there is a lot of depth here and the later levels become very tricky. It's the kind of game in which you get as much out of it as you put in. A true indie puzzle gem.