World of Goo is a physics based puzzle / construction game. The millions of Goo Balls who live in the beautiful World of Goo don't know that they are in a game, or that they are extremely delicious.
It's very hard not to give this game a perfect score. It's got that strange addictive quality like when you pick up a rubick's cube and start trying to solve it. In this game you experiment by building different structures out of sticky goo balls in an attempt to reach the goal. The game has plenty of levels and it manages to feel fresh all the way to the very end. If you don't already own this game 5 times from all the Humble Indie Bundles it's been in, definitely buy it.