You are standing at the end of a road before a small brick building. Around you is a forest. A small stream flows out of the building and down a gully.
The Colossal Caves Adventure was not, by far, the first computer game, but it did create and define the adventure game genre, which should remain dominant for about twenty years. And, of course, it introduced the magic word xyzzy.
Originally, it was created as a fairly realistic cave simulation by Willie Crowther, mainly for his daughters, but it soon spread across the then still very small Internet. Four years later, Don Woods came across it, contacted Crowther by sending emails to crowther@... every computer then online, and after getting his permission, expanded it with a Tolkienesque population.