You have two players, one player is the one playing in the game, player two is the one designing it as you go and deciding what happens.
Watch the slideshow, the guy who walks around and talks, and you see actions like 'blow', 'pick', etc, that's P1.
P2 is doing everything else. Deciding what people say, what happens. Ex; 'Blow' in the slideshow turned off the candle. P2 has to job of deciding what happens when it got blown out. Making it dark, turning the light off.