Colossal Cave Adventure

Colossal Cave Adventure, often known simply as Adventure and by its six-character file name ADVENT, is a text-based adventure game in which the player explores an underground cave system in search of hidden treasure, entering one- or two-word commands that a program interprets and responds to as a narrator.¹⁴¹ Written by Will Crowther in 1976 in FORTRAN for the PDP-10? mainframe and substantially expanded by Don Woods in 1977, it is the first well-known work of interactive fiction and the first well-known adventure game, giving the genre its name.¹⁶¹⁴

Origin

Crowther was a programmer at Bolt Beranek and Newman in Cambridge, Massachusetts, where he was writing what would now be called firmware for the earliest ARPANET routers.¹¹⁴ He was also an amateur spelunker who had explored the Mammoth Cave system in central Kentucky and created a vector map from surveys of parts of the real cave.¹⁴ In Crowther’s account, he wrote the game after a divorce left him missing his children and having given up caving, intending “a re-creation in fantasy of my caving” that would also be a game for his kids and would draw on the Dungeons & Dragons he had been playing.¹⁸

Crowther deliberately made the player direct the game with natural-language input rather than more standardized commands so that it “would not be intimidating to non-computer people”.¹⁸ The cave setting was drawn from the real Colossal Cave section of the Mammoth Cave system; the world’s longest cave lies beneath central Kentucky, its limestone passages stretching some 400 miles.⁶ Crowther’s ex-wife, Patricia Crowther, was herself a caver whose survey maps of the cave underlay the game’s geography.⁸ Several real locations and artifacts — an iron rod and an axe head among them — correspond to their representation in Crowther’s version, though he introduced subtle changes to the environment to improve the gameplay.⁷

The original consisted of roughly 700 lines of FORTRAN code and about another 700 lines of data, requiring some 60K words — nearly 300KB — of core memory to run.¹⁴ A study drawing on source code recovered from a backup of Woods’s Stanford account and an excursion to the real cave established that Crowther wrote the game during the 1975–76 academic year and probably abandoned it in early 1976; the original already employed magic, humor, simple combat, and basic puzzles, including fantasy elements such as an axe-throwing dwarf and a magic bridge.⁷¹⁴

The Woods expansion

Adventure as it is generally known was released by Don Woods on a PDP-10? at the Stanford AI Lab on June 3, 1977, some sources erroneously dating it to 1976.¹ Woods, a student at Stanford, had found a copy of the game and asked Crowther’s permission to expand it.¹⁵ He greatly enlarged the fantasy content and added significant technical innovations, including scorekeeping and a player inventory.⁷ His release, in which the player can earn a maximum of 350 points, became the iconic version and the ancestor of most later ports; it is sometimes called 350-point Adventure or Adventure 350.¹⁶¹⁵

The game begins with the player standing in a forest next to a building near a locked grate leading down into the cave.¹⁵ Inside the building are keys, food, water, and a lamp; the player unlocks the grate, lights the lamp, and descends.¹⁵ Play involves mapping the cave by hand, since some passages do not connect symmetrically, managing limited inventory space and a lamp that will run out, and solving puzzles to collect fifteen treasures and return them to the building.¹¹¹⁷ The game contributed the magic word “xyzzy,” which teleports the player between the debris room and the building and has since survived as an Easter egg in games such as Minesweeper.¹⁵¹⁴ Woods’s later work added a turn limit to force efficient play, replacing an earlier “batteries” mechanic that had instead encouraged players to prolong the game.¹

Ports and later versions

Between 1977 and 1995 Crowther and Woods continued to work on the game intermittently, a mainline of development that culminated in the 1995 release of Adventure 2.5, also known as 430-point Adventure, which added five new treasures and their puzzles.¹ The earliest port to C was made by Jim Gillogly under an early Unix at the Rand Corporation in 1977; this version was later included in the BSD Games collection and remains distributed as the adventure command on modern BSD and Linux systems.¹² Many others ported and extended the game; a notable version was the first game shipped for the IBM Personal Computer in 1981, for which neither Crowther, Woods, nor Gillogly were paid royalties.¹ It was later included with the floppy-disk distribution of Microsoft’s MS-DOS 5.0.¹⁴

In February 2017, Eric S. Raymond, researching the history of text adventures, discovered Adventure 2.5 and wrote to Woods for permission to release it under an open-source license; Woods granted permission on May 15, 2017.¹ Raymond published the result as Open Adventure under a two-clause BSD license, translating the FORTRAN-derived C into modern idiomatic C and moving the game’s cryptic room-and-object database into YAML while preserving the exact gameplay of 2.5.¹¹⁶ In 2023, Ken and Roberta Williams released Colossal Cave, a 1:1 three-dimensional remake built in a game engine, reproducing every room of the original with voiced narration.¹³¹¹

Influence

Adventure is described as the origin of all later dungeon-crawling computer games and the “granddaddy of interactive fiction”.¹ Its popularity led to the wide success of interactive fiction in the late 1970s and 1980s, and it directly or indirectly gave rise to the entire corpus of text adventures and, by extension, graphical adventure games.¹⁴¹⁶ It inspired Zork, whose starting building and treasure-return structure closely echo Adventure, and games including Rogue.¹⁵¹¹ Designers of later roguelikes frequently cite Adventure as an influence.¹ It also inspired Roberta Williams, co-founder of Sierra On-Line and creator of King’s Quest, directly influencing the Williamses to found the company.¹¹¹⁵ In video game history, Warren Robinett’s Adventure for the Atari 2600 was itself inspired by Colossal Cave Adventure.¹⁹

Crowther drew on the tabletop role-playing game Dungeons & Dragons for the fantasy and combat elements of the game.¹⁸ Two earlier computer games are sometimes named but discounted as antecedents: the PLATO dungeon-crawler “dnd” (1974–75) and Gregory Yob’s “Hunt the Wumpus” (1972), neither of which appears to have been known to the ARPANET- and minicomputer-centered culture Crowther and Woods worked in, and neither of which used a natural-language parser even as primitive as Adventure’s.¹