Zoo Tycoon

In challenge mode, you'll be given 3 goals at a time, which can be viewed by pressing down on the d-pad. They can range anywhere from taking a picture of a specific animal to buggy races to refill your concessions to maintaining a green level of animal/guest happiness for xx minutes. The easiest challenges are the animal/magazine photographs, which require you to take a picture of certain animals. Though, honestly, if you play challenge mode for about 10 minutes, you'll probably just finish one on accident.