Gameplay
The game features significant changes and improvements to the series' basic gameplay. Chaos Theory is also the first game in the Splinter Cell series to use ragdoll physics.[16]
Chaos Theory features refined stealth mechanics. In addition to the standard light bar, the game also features an aural monitor that measures Sam's noise, along with the ambient noise of the environment. It is important for Sam to make less noise than his surroundings; otherwise, the enemy guards will hear him. The more sounds the player makes will gradually increase the stress levels of the guards, and they will become more alarmed as the level progresses.
The artificial intelligence in general has received an overhaul to its design ranging from how they interact with the environment, to interacting with each other. They will move furniture to create cover, detect changes in the environment (such as whether or not scanners have been hacked, lights have been shot or turned off, doors left open, and materials have been cut), will use team-based tactics to provide covering fire and flank Sam, and even light flares in dark environments to possibly reveal where the player may be hiding, and even detect Sam through seeing his reflection in a mirror. Certain levels of alarm in a level may also cause them to don heavier armor and create choke points, cutting off access to certain entry-ways, attempting to ambush Sam.[17]
The AI detection has been altered as well. After Sam left an area in former titles, the game would sweep the previous area for all unconscious or dead bodies in a well-lit spot. If any were found, an alarm would be triggered. In Chaos Theory, the bodies must be discovered by a patrolling guard or security camera to trigger an alarm.
Being spotted by enemies will still trigger alarms, and alarms will still cause enemies to become more alert and combat-ready (such as causing them to wear ballistic vests and helmets). However, triggering too many alarms will no longer cause the game to end automatically. Even killing civilians or friendly soldiers may not cause Fisher to fail the mission, although doing so will at least cause Fisher to be severely chastised by his superior and cost him significantly his mission score, as well as cancelling some mission objectives, such as tapping phone lines and locating covert listening devices.
Chaos Theory adds a combat knife to Sam's close-quarters combat abilities.[18] Sam can use the knife in multiple ways, such as threatening an enemy during an interrogation, killing an enemy in close-quarters combat, breaking door locks as opposed to picking them, or piercing gas tanks on generators to aid in his stealth operations. Also, it no longer matters what direction Sam attacks from when using melee attacks, nor does it matter if enemies are aware of his presence, as opposed to earlier entries in the series where he had to attack from behind or on the side and the enemy could not be alerted to him in order to take them down in one hit. Sam also can use lethal or non-lethal force when ending an interrogation and with his close-range attacks. As an expansion on Sam's ability to shoot while hanging upside down (introduced in Pandora Tomorrow), he can now choke down or break the neck of enemies below him. He can also pull people over railings while hanging off a ledge and throw bodies off cliffs or over railings, even onto other guards. However, the ability to shoot around corners has been removed, but this is balanced by being able to switch the side of Sam's body the gun is on while in a firing position.
In terms of weaponry, Fisher can choose from one of three different equipment "kits." There is Redding's recommended kit, an assault kit and a stealth kit. Redding's Recommendation gives Sam an even balance between ammunition and non-lethal weaponry. Assault provides more ammunition at the expense of non-lethal weapons, while the Stealth kit contains more non-lethal weaponry but less 'brute force' which means reduced lethal weaponry and spare magazines. On missions where an objective is to cause no fatalities, the player cannot choose the Assault option.
The 5-7 SC Pistol returns, though the laser pointer featured in Pandora Tomorrow is replaced with a new feature: the OCP (Optically Channeled Potentiator).[19] When fired at certain electronics, the OCP can disable them for a limited time. Fisher can disable lights, security cameras, and more. If the device cannot be disabled, it will temporarily malfunction, such as causing the blue screen of death when attacking computer towers. When Fisher successfully disables the electronic device he aimed at, a green light appears on the pistol; if he misses, a red light appears. In both cases, Fisher must wait for the OCP to recharge and become ready for use again.
The SC-20K returns with many new attachments, such as a foregrip that reduces recoil and increases accuracy, a launcher that fires non-lethal weaponry, an under-barrel shotgun attachment for close quarters firing, and a prototype 20mm sniper attachment for long-range combat. The SC-20K now uses a reflex sight that zooms to 1.5x magnification, while the sniper scope allows from 1.5x to 3.5x magnification.
A large variety of non-lethal weaponry can be fired from the SC-20K launcher, such as the Sticky Camera, the Sticky Shocker, the Airfoil Round, and the Gas Grenade. The Sticky Camera will reveal an image of the area in which it was shot. It can also make a clicking sound that will attract enemies and emit a CS gas that will render any enemies in the immediate area unconscious. In contrast to former titles, Sam can now use multiple cameras simultaneously. He can switch back to any Sticky Camera that has not been destroyed by using the CS gas attack or due to enemy fire. The Sticky Shocker will shock and incapacitate its target when fired. If shot into a body of water, the shocker will incapacitate all targets in the water. The Airfoil Round is a hollow metal ring that will knock out the target. It is still possible for an unconscious enemy to die if shot, dropped from a considerable height or dropped into water, no matter how shallow.
Fisher also has multiple types of grenades.[20] There is a gas grenade, which emits a cloud of CS gas that knocks enemies unconscious, a smoke grenade, which provides Fisher with a cloud of smoke to hide in, the flashbang, which will temporarily blind and deafen any enemy near it, and the fragmentation grenade, which will kill any enemy within its blast radius, and send objects flying in all directions. The Wallmine also returns from previous installments; a wall-mounted explosive equipped with a motion sensor that detonates when enemies move in front of it.
Multiplayer
Chaos Theory features competitive and cooperative multiplayer. The cooperative mode expands play by allowing two agents to play through a unique seven-mission story mode that parallels the single-player campaign. It is playable via system link or over Xbox Live. The cooperative campaign follows the story of two Splinter Cells in training, merely known as Agent One and Agent Two. Their training is interrupted when a world crisis occurs that requires the Shadownet division of the NSA to deploy additional resources, even including agents not adequately trained. The missions become a trial by fire for the two new agents. Though players can operate alone, the level design is such that it encourages teamwork. Ubisoft eventually developed two additional levels for download for the PC and Xbox versions. The Nuclear Plant and UN Headquarters missions are meant to end the story for the cooperative component.
In Splinter Cell Chaos Theory VS mode, two additional gameplay modes have been added to the game. New game modes include disk hunt, which consists of spies grabbing disks placed throughout the level, then returning the disks to their extraction point. The other game mode is deathmatch, which consists of killing players on the opposite team-spies or mercenaries.
The Spy vs. Mercenary game mode returns from Pandora Tomorrow with many improvements. These include new gadgets for both teams, cooperative moves for the spy team, and improved close-quarters combat for the mercenaries. Spies are armed with non-lethal weaponry and rely on stealth, skill, and gadgets. Spies can only kill mercenaries by breaking their necks, dropping on them, and hanging from a ledge and pulling them down. The spies' gadgets also do not generally affect other spies. Mercenaries are the heavily armed enemies of the SHADOWNET spies, who have access to lethal weaponry.
