Ah, the summer of 1961.

JFK worried about Earth war, not Spacewar!

United States President John F Kennedy was coping with the aftermath of the Bay of Pigs invasion, Berliners were learning to live with the wall, the Beatles were singing up a storm at the Cavern club, and in Boston a small group of programmers were about to invent the computer games industry.

Yes, it's 40 years since a band of pioneering computer enthusiasts created Spacewar!, in which players battled to save the Universe.

Most computers at that time were huge, expensive machines tended by men in white coats who defended their whirring, clicking charges with all the high-minded zeal of, well, zealots.

Game on

But the appearance of computers such as the TX-0 at Massachusetts Institute of Technology (MIT) changed all that.

Spacewar! was a marvel of getting more from less

Barry Silverman, who has put the game online

It used transistors instead of tubes as its computational substrate, had a cathode ray tube output device and was programmed via a keyboard that produced printed tape with which to feed the machine.

But best of all, as far as fledgling computer boffins who flocked to it were concerned, the computer could be programmed directly.

No longer did they have to deal with an arrogant, white-coated intermediary. Instead, they could pull up a chair and play around. They could hack, experiment, and show off their programming prowess. They could play games.

Enter the vortex

Well, almost. Before they could play games they had to create them.

The task fell to a group of proto-geeks enthused by the possibilities of the shocking amounts of computer power suddenly available - about that of a modern day palmtop computer.

Inspirational: The work of EE Doc Smith

The informal group, some of whom were students at MIT, included Dan Edwards, Alan Kotok, Peter Sampson, J Martin Graetz and Steve "Slug" Russell.

All were huge fans of science fiction, especially the space operas of cereal chemist E E Doc Smith who, as Mr Graetz notes, "wrote with the grace and refinement of a pneumatic drill".

The stories of Doc Smith typically revolved around a group of spacemen who, armed only with ray guns, brains and spaceships, blast off into the ether to tackle a cosmic criminal cabal.

Power trip

Giddy with the power of the TX-0 and another MIT computer, a DEC PDP-1, the group decided to recreate the galactic vista of Doc Smith's work using the 30 line display and mighty nine kilobytes of memory available on the PDP.

The Beatles: Sound of 1961

So, that summer, they went to work. Slug Russell did most of the grunt work involved in programming the game, which simply had to have the name Spacewar!.

War is actually rather too grand a name for a game that pits two rockets equipped with missile launchers against each other. But the contest is made more interesting by the black hole at the centre of the screen that gradually sucks the ships in unless they use their thrusters to escape its insidious pull.

The trick is to work out how to use the gravity well created by the black hole to slingshot towards your opponent and unleash a barrage of missiles before heading off screen to safety.

Live web show

You can play the game yourself, since a web version of it has been recreated by three historically minded programmers.

"Spacewar! was a marvel of getting more from less," says Barry Silverman, one of the team who put the game online. "The code size for Spacewar! was two kilobytes, yet they created a game that is still quite playable."

Brian Silverman, brother to Barry and another on the team, said programming had changed significantly since 1961, when it had more to do with mathematics than engineering.

But, he said, one trait shared by the Spacewar! creators with every game designer since is the fact that no matter how much power they had at their fingertips, it was never enough to realise their dreams fully.

"What video game designers do is squeeze the last bit of juice out of the lemon," said Mr Silverman. "The lemon has just got a lot bigger".