Like the series, the game takes place over 24 hours and has the same start and end clocks for each hour, marking the start and end of each part of the game. The hours are broken down into 58 separate missions, of which there are three broad types, each described in further detail below. Some missions are objective based, while others have a time-restricted element. Each mission is graded out of 100 points, based on the quality of performance, number of objectives completed, shooting accuracy and so on. A grade of 90 points or higher rewards the player by unlocking some form of bonus feature, including 3 movies (interviews with cast about the game, TV promos), 98 images (wallpaper-like images of main characters) and 23 characters (3D models that the player can view). Most of the game's missions take place in third-person shooting format, although a unique aspect at the time was the use of cover. When a character is behind a low object like a crate, or at the edge of a corner or doorframe, they can press a button to use the object or edge as cover. Another button will allow the character to peer around and enter a targeting mode, while releasing the button will quickly return them to cover. There is also a stealth mode which has the character stoop, walk silently (unless running), duck behind any low obstacles they can hide behind and be less detectable by sound. A character can sneak up behind an enemy using stealth mode and perform a silent "stealth takeout" by breaking his neck. A variety of weapons are available including handguns, automatic weapons and shotguns, with various ammunition types also in existence. Ammunition is limited in the game and weapons must be reloaded, although additional ammunition can be collected. Players can also call out to enemies who will sometimes surrender and can then be captured (put in handcuffs) with their ammunition also collected. There are also civilians in the game who can also be called out to and then rescued by the player. Health bars for enemies, vehicles or friendly subjects that must be protected are also sometimes shown. There are health packs which can be picked up, as well as health stations mounted on walls which can be used. Body armor is also sometimes provided or found in levels. A small heads-up-display features a radar/map with an arrow showing the character's direction, red dots for enemies, green dots for civilians, and yellow stars for objectives. The direction and field of vision of enemies is shown on the radar. In third-person missions and occasionally some other types, a PDA is available. In the PDA the player can view their list of objectives (which can change over the course of a mission), maps of the area if available, a help screen and a list of weapons held with information on each. Characters also typically have cell phones which they sometimes receive calls on during missions. Some missions involve sniping using first-person shooter gameplay. These missions resemble the use of a sniper rifle during normal missions but the player cannot switch to a third-person view. There are several missions in which the player controls a motor vehicle. Though the game engine is the same as the third-person mode, these missions are based on being in a vehicle. They usually involve getting to a certain location in a certain time period, often while avoiding pursuers while heading to the end point. Weapons can not be used while in a vehicle. While the PDA is not available in these mission types, a map of the city is. Cell phone calls are also sometimes received in these missions.