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http://www.destructoid.com/until-daw...s-279599.phtml
Until Dawn is all about player choice, offering thousands of play paths that lead to hundreds of possible endings. A lot of this is tied to one of the game's mechanics called the Butterfly Effect.
This is important as Until Dawn was designed so that every character can survive and/or die. And if they die, they stay dead -- no restarts here. The game will adapt the story if a character dies, so every decision you nmake can alter the story completely.

During some of these choices, a small butterfly icon will appear in the upper right side of the screen. This indicates that the Butterfly Effect is underway. Pulled straight from chaos theory, the butterfly effect has it so that any one small change can bring about larger changes further down the road. For the purposes of Until Dawn, any one choice you make can have you going down any one path, eventually ending up at one of any of the hundreds of endings.