This first ever computer game has many features of so-called modern games. To put it into a historical context: this game was conceived in 1961 – 17 years after the end of WWII, before manned spaceflight, a year before the mouse was invented and the same year that Ivan Sutherland invented “SketchpadARPAnet.
The developers were Stephen Russell, Peter Samson, Dan Edwards, and Martin Graetz.
The game itself runs to 9kb of memory and 40 pages of listings.
SpaceWar may be the most important computer game ever. The first version was developed for the PDP-1 at MIT in 1960(!). The game has been under essentially constant development since.
The first CRT display was a converted oscilloscope used to play SpaceWar. The first trackball (and thus, the first mouse) was a SpaceWar control at MIT. It is said that Ken Thompson salvaged a PDP-1 and created a new operating system, now called UNIX (!), so that he could play SpaceWar.