Last weekend I visited an old friend - a pub about fifteen miles away, which was once a regular haunt of mine in my younger days. The last time I went there, the pub was still a proper, old-school rock establishment with lager on the floor, ketchup on the bar and a row of motorcycles ranked up out the front.

In these days of family friendly establishments with their two-for-a-fiver microwave meals, plastic slides and Sky News, it seemed almost unimaginable that my favourite boozer could possibly survive. Thankfully, I was wrong.

The first chap I bumped into wore a deity's beard and was topless apart from a high visibility jacket and a vast pair of shades. The second chap I bumped into looked like the lead singer from White Snake. Somewhere off in the corner of the room, a metal band emitted a cacophonous mixture of high pitched squeals and bottom-trembling bass, roughly akin to a herd of swine being fed into a wood chipper.

And there, opposite the band, standing as incongruous as the TARDIS and almost as big, was an original Space Invaders cabinet, complete with the tatty, peeling graphics of aliens all down the side. It was the first proper one I'd seen in nearly a decade.

Like the pub it stood in, the Space Invaders machine was a throwback to another era, one even I'm too young to remember - it's hard to imagine now, but this was once the biggest game on the planet, even becoming so riotously popular in Japan that entire arcades were devoted to this one cabinet, where coins were thrust into them faster than the Nippon mint could produce them.

Played in 2009 - even after several beers - Space Invaders is a bizarrely austere affair, with a mere handful of sound effects, colour crudely simulated using strips of tape and interaction limited to left-right-shoot. And yet these few elements come together in a game that still provides a perverse thrill of enjoyment, not least because of its well documented programming quirks: creator Tomohiro Nishikado freely admits that the gradual increase in the aliens' speed as their numbers diminish was due to hardware limitations, an oddity that actually makes the challenge far more addictive than it might have been - the initial heart beat thump as the invaders descend gradually giving way to a frenzied thrum as you struggle to hit the last alien.

The technique that became known as 'the wall of death' was also put in apparently by mistake: when the aliens descend to the penultimate row, their bullets don't destroy the player's base - a glitch which can be exploited by the skillful to rack up a vast amount of points.

What's most remarkable about Space Invaders' success is how well it has endured - while other companies created other shooters that expanded on its idea (Galaxian, Galaga, Moon Cresta, Phoenix, and so on, right up to the shooters of today), Space Invaders has never been quite forgotten.

Indeed, it's interesting to note just what did - and didn't - change in the various iterations that came and went over the years: Space Invaders II and Space Invaders Deluxe added a splash of colour and some fresh varieties of alien; Space Invaders 91 (AKA Space Invaders Part 4, AKA The Majestic Twelve) added power-ups and a brilliant cattle theft bonus stage; and the seldom discussed Space Invaders 95: The Attack Of The Loonies went down a bizarre Japanese comedy route reminiscent of Konami's Parodius. And while some experiments with the franchise ultimately lead to disaster (see the largely unrelated Invasion Day mentioned here last week, and the dull excursion into wireframe 3D which came as part of Space Invaders Anniversary for the PS2), the original gameplay has still survived intact in the vast majority of Taito's sequels.

Space Invaders Extreme, which appeared for handhelds last year and more recently for XBLA, is an example of just how exciting the game can be with a bit of imagination: with psychedelic visuals and a Pete Tong sound track, it's Space Invaders in a night club on dubious pharmaceuticals. It's also Space Invaders for the attention deficit generation, with a constantly rotating blur of bonus rounds, power ups and bizarre alien battle formations.

And thanks to Extreme's faithfulness to the seventies Space Invaders ethos - left, right, shoot - it's bloody marvellous, and proof positive that a thirty year old game can still just about cut the mustard in a modern gaming landscape.

The chipboard cabinets with their cigarette burns and peeling vinyl may be museum pieces now, and the arcades that held them long gone, but Space Invaders' beating heart never quits.

Ryan writes his gaming column every week at Den Of Geek. Last week's is here.