Reverting to the World War II storyline of the original Call of Duty games, Call of Duty: World at War is another first-person shooter developed by Treyarch and Exakt Entertainment, and published by Activision in 2008. Available on Microsoft Windows, PlayStation 3, Nintendo Wii, and Xbox 360, World at War focuses on the Pacific and Eastern fronts involving the United States, Japan, the USSR, and Germany. Single-player campaign mode can be played from the perspectives of several different soldiers, and each campaign presents a unique and emotionally-driven experience. Based on historical battles such as the Battle of Peleliu, the single-player campaigns consist of several missions in large landscapes. Missions usually require the completion of multiple objectives, and an on-screen compass aids the player in reaching progressive checkpoints. Single-player campaign mode features four difficulty levels: easy, regular, hardened, and veteran. Increased difficulty means more strategy and lengthier gameplay. Single-player also introduces a new feature of thirteen hidden death cards that can be collected on each level and used to unlock cheat codes for cooperative play. World at War utilizes the same ranking and reward/perk systems as Call of Duty 4: Modern Warfare, as well as the six multiplayer modes and the killstreak feature. Less linear than other Call of Duty games, World at War leaves the player multiple paths to complete objectives. Since WWII forms the backdrop to this game, older equipment and weapons return to the game. Two new and notable weapons include flamethrowers and bayonets. Critics and gamers generally applauded World at War, especially its realistic use of actual WWII videos, photographs, and statistics during chapter cutscenes.