Age of Empires II: The Age of Kings (often shortened to AOE2, aoe2, AoE II or AoK) is a real-time strategy (RTS) video game developed by Ensemble Studios and published by Microsoft. Released in 1999 for the Microsoft Windows and Macintosh operating systems, it was the second game in the Age of Empires series. An expansion, The Conquerors, was released in 2000. A PlayStation 2 version was released by Konami in 2001, and a Nintendo DS spinoff, Age of Empires: The Age of Kings was developed by Backbone Entertainment in 2006. The Dreamcast port, by Konami, was canceled.