Keith Lee, chief executive of location-based game company Booyah, said today that his team built its new Facebook Places location app — InCrowd — in just three weeks. The app lets users interact with friends and share posts in real-time in real-world locations.

InCrowd is coming soon to the iPhone, iPod Touch, and iPad, and it is powered by Facebook Places. Facebook chief executive Mark Zuckerberg unveiled Facebook Places to the world today at the company’s press event at its headquarters in Palo Alto, Calif. Zuckerberg said the product serves three main goals: To let users share their location with friends, to see where their friends are, and to discover new places.

Lee got to go up on stage and explain his company’s new app, which is launching today and will build game-like features into a location-services environment. As soon as his company got its hands on Facebook’s new applications programming interface (API) for Facebook Places, it immediately started working on a brand new app. Booyah makes the popular MyTown monopoly-like location-based game, which has 3.1 million users, as well as the Facebook app, Nightclub City, which has 6.5 million players.

But Lee said the company decided to take advantage of Facebook Places using a brand new design rather than adapt its existing apps. With InCrowd, players can broadcast their locations of the places they love to their friends, while still adhering to Facebook’s privacy settings.

Players become more popular when others respond to their own actions, such as “booting them in the rear,” “sending them a wink,” or posting about a venue. Here’s our video with Lee, on location at Facebook: