 The first Halo game was announced on July 21 , 1999 , during the Macworld Conference & Expo . It was originally planned to be a real @-@ time strategy game for the Mac and Windows operating systems , but later changed into a third @-@ person action game . On June 19 , 2000 , Microsoft acquired Bungie Studios and Halo : Combat Evolved became a launch title for the Xbox video game console . After receiving Xbox development kits , Bungie Studios rewrote the game 's engine , heavily altered its presentation , and turned it into a first @-@ person shooter . Though the first Halo was meant to include an online multiplayer mode , it was excluded because Xbox Live was not yet available . 
