Space Flight by Paul Lutus
Try to land a spacecraft with a calculator
This “open source” simulator was writen around 1972 and published in 1977 - long before open source movement came to existance and a little bit before it’s author got his first computer. And it runs (flies?) on a scientific calculator with a segment-display.
Paul Lutus has become a legend among computer enthusiasts thanks to his brilliant career from a self-taught electronics technician to a NASA engineer. He is also a programmer who was the first one to work remotely in the 1970s.