Lunar Lander (Text Game)

The original Lunar Lander game was a 1969 text-based game called Lunar, or alternately the Lunar Landing Game. It was originally written in the FOCAL programming language for the Digital Equipment Corporation (DEC) PDP-8 minicomputer by Jim Storer while a student at Lexington High School in the fall of 1969. Storer submitted the game to the DEC users' newsletter, which distributed the source code to readers. Other versions of the concept were written soon after: a version called Rocket was written in BASIC by Eric Peters at DEC, and a third version, LEM, was written by William Labaree II in BASIC, among others.

All three text-based games require the player to control a rocket attempting to land on the moon by entering instructions to the rocket in a turn-based system in response to the textual summary of its current position and velocity relative to the ground. In the original Lunar, players controlled only the amount of vertical thrust to apply, based on their current vertical velocity and remaining fuel, with each round representing one second of travel time. Rocket added a simple text-based graphical display of the distance from the ground in each round, while LEM added horizontal velocity and the ability to apply thrust at an angle. In 1970 and 1971, DEC employee and editor of the newsletter David H. Ahl converted two early mainframe games, Lunar and Hamurabi, from the FOCAL language to BASIC, partially as a demonstration of the language on the DEC PDP-8 minicomputer. Their popularity led him to start printing BASIC games in the DEC newsletter, both his own and reader submissions.

In 1973, Ahl released the book 101 BASIC Computer Games, which contained the source code of computer games written in BASIC. The games included were written by both Ahl and others and included both games original to the language and games ported from other languages such as FOCAL. 101 BASIC Computer Games was a landmark title in computer games programming and was a best-selling title with more than 10,000 copies sold. Its second edition in 1978, titled BASIC Computer Games, was the first million-selling computer book. As such, the BASIC ports of mainframe computer games included in the book were often more long-lived than their original versions or other mainframe computer games. Included in the book were all three versions of Lunar Lander, under the names ROCKET (Storer version), ROCKT1 (Peters version), and ROCKT2 (Labaree version). Ahl and Steve North then converted all three versions to Microsoft BASIC and published them in Creative Computing magazine and the Best of Creative Computing collection in 1976; they were reprinted in the 1978 edition of BASIC Computer Games as Lunar, LEM, and Rocket as the most popular of the existing versions of the game.

Lunar Lander was commercially distributed for some programmable calculators such as in 1975 for the Hewlett-Packard HP-25. With the advent of home computers in 1977, the game concept soon moved to those systems as well, with Moon Lander (1977) for the MK14 computer kit, which displayed the lander's speed, height, and fuel consumption on an eight-character calculator-style display, as an early example. While Ahl did not list a common name for the three similar titles in his book, the style of game was collectively seen as its own subgenre, with InfoWorld referring to LEM in February 1979 as "a lunar lander" and Antic terming the set of text-based games as "Lunar Landers" in 1986.

## In the Timeline

Lunar Lander is set during the 1969 Apollo 11 moon landing. However it doesn't change anything about this event. Thus, the moon landing goes the same as it does in our timeline.