Naughty Dog is trying something new with The Last of Us Part II, aiming for heart-pounding realism and immersion. On the subject of heart-pounding, every character in the game will have a heartbeat ? from the protagonist Ellie to all the enemies you?ll encounter. Depending on the situation, Ellie?s breathing will change. So whether you?re near enemies, running around, in the middle of a heated firefight, you?ll notice variations in the character?s breathing and heartbeat. Likewise, all the enemies will share this same technology.
Here?s what the game?s co-director Anthony Newman had to say about The Last of Us Part II?s new heartbeat system:

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