The Thinking Cap allows you to build on your property. Originally, the thinking cap was a black top hat and had 3 ranks, which allowed you to do different things. For example, you needed the Rank 3 Thinking Cap to play Gnarled Forest Survival. However, this was scrapped. They replaced it with a futuristic-style hat, and removed the ranks, but still kept the building abilities.
Gallery[]
Rank 1
Rank 2
Rank 3