"I get the same thrill playing World of Goo that I got while playing the previously mentioned Incredible Machine series. You are given an objective and all the tools/Goo you need to complete the task. You know you have what you need, but sometimes still swear it "can't be done." Take a break, come back and voila - it works. You can replay the levels if you wish, and share your successes with the online Goo-munity (I just made that term up!). Since it does not have the depth that other puzzlers have, playing and competing in that manner gives it a bit more replay value."