Jigsaw is an interactive fiction (IF) game, written by Graham Nelson in 1995. It begins at the turn of the 3rd millennium, with the player discovering a time machine enabling him or her to travel throughout the 20th Century, visiting many of its most historic moments. The game has been described as "acclaimed." It is widely recognised as a major achievement in its genre, particularly for the inclusion of a romantic relationship between the player and a central character whose gender is never revealed, allowing the player to project the gender of his or her choice onto the character. Although including many original ideas, it also contains references to many famous IF games, most notably Trinity.