Blizzard's first attempt at a role-playing game was a resounding success. Taking ideas found in early mainframe computer titles like Rogue and Hack, 1997's Diablo featured randomly generated dungeons filled with untold dangers behind every corner. Three character classes offered unique abilities to help survive the hellish environments lurking beneath the lonely town of Tristram. The dark and foreboding atmosphere, action-oriented combat, simple controls, and random "loot" helped invigorate the genre. Heroes could even team-up online with Blizzard's Battle.net service, which was notable for its free cost and seamless integration within the game.