In 2003, Infinity Ward developed a first-person shooter game that later became part of a huge franchise. Published by Activision, Call of Duty can be played on PCs, Xbox, and PlayStation consoles. Call of Duty is a military simulation game that focuses on infantry warfare during World War II. A player chooses whether they act as an American, British, or Soviet infantry soldier, fighting the Third Reich from different fronts. Each campaign possesses a different storyline, complete with authentic weapons based on time period and nation. Single-player campaigns consist of 11 espionage and assault missions in large landscapes. Missions usually require the completion of multiple objectives, and an on-screen compass aids the player in reaching progressive checkpoints. Call of Duty possesses a unique feature that other contemporary first-person shooters did not necessarily utilize: AI involvement in single-player gameplay. Artificially intelligent allies support the player during missions, providing cover and drawing enemy fire. In very few missions is the player totally alone. Multiplayer deathmatches can be played in either a four-way free-for-all or in team format, using special maps and employing a Bluetooth capability that allows communication between players. This original Call of Duty game also features several aspects of gameplay that developers changed later in the franchise. First, a player can save and load at any time, so as not to lose progress. Second, the concept of health fluctuates. Call of Duty features a health bar with Medkits scattered around levels to restore health. In subsequent games, health is restored when a player is not under fire, and no health bar exists. Furthermore, Call of Duty displays shellshock after the discharge of a particularly close weapon, meaning that a player's hearing, vision, and physical ability can be impaired. Developers wanted to achieve engrossing and realistic gameplay that accurately depicts the atmosphere of warfare. The success of Call of Duty prompted an expansion pack in early 2004 titled: Call of Duty: United Offensive, plus several sequels and spinoffs in later years. Call of Duty won several prestigious awards, including 2003 Game of the Year from the Academy of Interactive Arts & Sciences.