Back in 1967 the world witnessed its first interactive film, Kinoautomat, during which a moderator appeared on stage and stopped the film at nine "decision" points, asking the audience to vote on the direction - one of two choices - in which the film should proceed.

BBC: Many Worlds: The movie that watches its audience

She went to the top of her stairs, leaned over the bannister, and shouted in the direction of the hall door, asking who was there.

NEWYORKER: Bravado