Lunar Lander (also known as Moonlander) is an early computer game that runs on the DEC GT40 and DEC VS60 graphics terminals (typically downloaded from a PDP-10 mainframe or PDP-11 host computer). DEC commissioned the game to be written in 1973 as a demonstration of the capabilities of the GT40; it was seen at many trade shows.
The goal was to correctly land a lunar module on the surface of the moon using the game’s telemetry data. If the player miscalculates the module’s landing, the module will either fly off into space or crash hard against the moon’s surface or the mountain over which the lander first passed. The interface was through a light pen and the output display was a vector graphics system; the light pen allowed adjusting the throttle value and the angle of the lunar lander. Sophisticated players could achieve a landing on the mountain while cheaters learned the address of the word of magnetic core memory in which the fuel value was stored.
Later versions offered the ability to run the game on a free-standing RT-11 system as well as an Easter egg: a specific landing site offered a McDonald’s restaurant. Upon landing successfully near the restaurant, an astronaut would walk over to get lunch. Crashing into the restaurant destroyed it permanently (until the program was reloaded) and displayed an amusingly sarcastic message berating the player.