Space Travel, written by Ken Thompson on a Multics system in 1969, is a Top-Down View 2D Simulation Game of flight around our solar system. You fly a spaceship, flying to and landing on the planets and their moons. It's a Wide-Open Sandbox with no goals or enemies. Just fly around. Each planet and moon exert a gravitational pull on your ship, changing its trajectory. Sizes, masses, and distances of of the planets and moons are all depicted realistically. Planets and moons follow orbits, but not realistically; the orbits are perfect circles and all on the same plane.
It's of historical interest because Thompson and Dennis Ritchie invented UNIX to port it to an unused DEC PDP-7. In that sense, it may be the most influential video game ever developed. You're most likely reading this page because of it.
Space Travel provides examples of:
- In-Universe Game Clock: The planets and moons following their orbits.
- No Plot? No Problem!
- Ragdoll Physics
- Simulation Game
- Top-Down View
- Wide-Open Sandbox: Probably the Ur-Example.