Colossal Cave Adventure

The Colossal Cave Adventure game, produced in the '70s, was the historic first "interactive fiction" game, in which the computer would simulate and describe a situation and the user would type in what to do next, in simple English.

The user would thus be a part of an ongoing story in a fantasy setting — in this case, an exploration of Colossal Cave in Kentucky. But this Colossal Cave, though remarkably similar to its real-life counterpart, was also very different:

Magic was afoot in the cave...

You are in a twisty maze of passageways, all alike...