 The games of the main Halo trilogy were developed by Bungie , and are first @-@ person shooters in which the player experiences most action from the protagonist 's perspective . The first title in the series is the Xbox version of Halo : Combat Evolved , released on November 15 , 2001 . The game was initially intended to be released for Windows and Mac OS , until Microsoft 's purchase of Bungie in 2000 led to the game becoming an Xbox launch title and platform exclusive . Halo : Combat Evolved introduced many gameplay and plot themes common to the whole trilogy . Players battle various aliens on foot and in vehicles to complete objectives , while attempting to uncover the secrets of the eponymous Halo . One concept introduced in Halo : Combat Evolved , is limiting the number of weapons players could carry to two , forcing them to carefully select their preferred armament . Players fight with ranged and melee attacks , as well as a limited number of grenades . Bungie refers to the " weapons @-@ grenades @-@ melee " format as the " Golden Triangle of Halo " , which has remained fundamentally unchanged throughout the trilogy . In Halo : Combat Evolved , the player 's health is measured in both hit points and a continually recharging energy shield ; the sequels forgo the hit point system , although it returns in spin @-@ offs . A Windows and Mac OS X port was later developed by Gearbox Software , and released on September 30 and November 11 , 2003 , respectively . A stand @-@ alone expansion , entitled Halo : Custom Edition , was released as a Windows exclusive , and allowed players to create custom content for the game . 
