Started as a PC game then Microsoft wanted it so they made a deal with Bungie to make it xbone exclusive. Bungie left Microsoft after Halo 2 but continued making games for there Xbone 360 console, then in 2011 Bungie sold halo because they knew it was dead, then a company called 343I was dumb enough to buy it and now makes low quality shit games for the same price as high quality Bungie games.