Firearms can now be used for executions.
A new feature to executions in the game are the environmental kills, which can be used to eliminate an opponent. For example, you can push an enemy face-first into a live fuse box, use telephone cords to strangle an enemy or you can beat an enemy to death in a toilet.
Loud ambient noises can now be exploited by the player to drown out their foes.
When hiding in shadows, if an enemy comes close to the playable character, the player will have to mimic a combination of buttons or motions in order to regulate the character's breathing to ensure that he remains calm and undetected. In the Wii version, the player must hold the Wii Remote completely still.
He player can smash lights to create extra pockets of shadow to be used for hiding.
Some lights are provided with a motion sensor that activates when detecting movements in front of it, forcing the player to investigate the dark corners before taking advantage of them.

That game is prohibited in more than 40 countries, if I don't make a mistake.

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source: Wikipedia