Connoisseurs of the early arcade machines and the 8-bit genre rejoice! Annihilating the descending centipede on the Electron comes in a variety of guises, all of them written in machine code and fairly faithful to the arcade original. It is a remarkably simple concept - a field of mushrooms provide obstructions and a long caterpillar moves through them, changing direction and moving one line down the screen each time it collides with one. You can play the game as you wish - some players aim directly at the caterpillar; others try to predict which mushrooms are potentially creating a dangerous area and take out these before getting down to the bug blasting.

As soon as you hit the caterpillar for the first time however, the action really picks up, because the caterpillar splits in two. So you now have two segments, both barrelling down the screen. Before long the player can be faced with a whole host of mini-caterpillars, baying for blood. Contact with anything is fatal. This format is common to all conversions. Some add even more spice to the gaming area by having infected mushrooms - these can cause any descending meanie who collides with them to do a murderous rampage down the screen stopping at nothing. Some have falling mushroom layers which clutter the playing area at random intervals. Almost all have a bouncing spider who terrorises the player by diverting his attention, even if the spider is usually quite easily dispatched with a single bullet.

The Electron had its fair share of clones of the "centipede" format, which was as popular as Asteroids (Came to the Elk as Meteors), Space Invaders (Arcadians) and Donkey Kong (Killer Gorilla). Most of them came in the very early months of the Eighties. For the purposes of this review we are looking at only those versions that were released by professional software houses for the Acorn Electron. If one also includes the clones that were published in mainstream computer magazines, the list does grow - and in 1986 the BBC Master also had its own clone, Aqua Attack, given away free with each purchase. The first publishers to get there with the Elk however were Superior Software, with Centibug.

It came out early in 1983 and was priced around the £7.95 mark. (As an aside, you might note that in interviews, Steve Hanson attributed much of Superior's success to these early games written by his brother Richard.) Standards for games at the time were not high, and the code is compact, with textual instructions and a skill level prompt being required before the game commences. There is also one of the most basic-looking high score tables you may ever see coupled onto the game over sequence. The machine code that comprises the game itself however fares better. Whereas you can actually see the textual screens being slowly built-up (Never hear of VDU 19,x,0;0;, Richard?), the mushrooms and bugs move swifty and the Mode 2 action zips along.

The main problem with Centibug is however that, even on the lowest skill level, it is practically impossible to win even a single sheet. First of all, there are far too many mushrooms, meaning that the Centipede practically sails down the top ten lines of the screen without a single shot getting through them. Also, the mushrooms do not, as on the arcade version, disappear when hit. No, no, no. When you hit a mushroom for the first time, your bullet makes a bullet-sized hole in it. The next shot you fire will pass through that hole and may just, if you're incredibly lucky, hit the centipede. More likely however, there will be another mushroom above it that will similarly stop the shot.

There's no tactical clearing of mushroom areas with this kind of scenario, and on top of this, you get a bouncing spider in the playing area at the base of the screen which often never bounces more than about two pixels higher than your laser base. The keys are simply Z, X and DELETE to fire so, you guessed it, there's no way of luring the spider away from the bottom of the screen then ducking under it and shooting it. On the contrary, this spider will get you every time it bloody well appears!

At about the same time, Alligata released Bug Blaster, an alternative Mode 5 Centipede clone where you struggle to pick out any obvious disparity with the arcade original. Firstly, there is a lot of room to manoeuvre in this version, not only due to the more appropriately sized sprites but also because you have the traditional ZX*? with RETURN to fire combination. The first sheet starts with only a small selection of mushrooms and, due to the bigger dimensions of the playing area, the Centipede has much more time to travel from one side of the screen to another. Hitting a mushroom takes a chunk out of it, your bullets travel extremely quickly and the whole experience is enlivened by the bobbing spiders that appear with a cacophany of high-pitched notes that rise and fall as they do. Shoot a spider and you get a large bonus which, helpfully, appears briefly on screen when the shot strikes home.

A scorpion shoots across the screen infecting mushrooms (as described above) and a mushroom layer occasionally does its job. Both can be wiped out with a hail of bullets if you are not too busy dealing with the pede when they make their appearance. However, because the mushrooms are destroyed quickly, it is easy to clear an area of mushrooms later in the day if you are!

Bug Blaster is zippy and great fun to play and, despite being released very early in the cycle of Electron games, definitely remains the definitive clone. Next we have the IJK version, Caterpillar, running in Mode 1 at a much less frentic pace. It has much the look of a Dragon 32 game with a green background, and sprites made up of 8x8 CHR$ definitions. Whilst the code is, as is clearly to be expected, done in machine code, its handling actually makes for a very different game to any of the others. A single shot destroys a mushroom and, indeed, so devoid of mushrooms is the playing area that it is possible to clear the entire screen of mushrooms if one puts one's mind to it.

The caterpillar is a combination of blobs, with very little detail (certainly no legs), and the spider is a monochrome 16x8 non-animated baddy. Both move jerkily, 8 pixels at a time, as if they were in fact being PRINTTABbed onto the screen. Yet despite all of these flaws, the game does work and is a fairly playable piece of programming. Your bullets whistle up the screen and there's a suitably diverse range of sound effects from other arachnids when they put in an appearance. The fact that you have the up and down motion in this version gives you a very large area that you can enter, getting yourself away from these dreaded adversaries if necessary. You can improve your game a lot with practice and are quite unlikely to become spider-, or even caterpillar-, food.

Romik's version, Caterpiller (sic) shares at least one 'quality' of Superior's version, in that it runs far too fast to make even clearing one sheet anything more than a dream. Again, it's a Mode 2 clone and the mushrooms are abandoned in this version in favour of what look like strawberries. Fine, but where at least Bug Blaster and the IJK version give one time to think, Romik's version launches with so much happening on screen that even allowing your eyes to look at the crawling caterpillar is usually a fatal move.

You have a sort of bug-eyed face playing the spider which, in this version, has the handy side-effect of wiping out any mushrooms he hovers onto. So, rather than blast him into oblivion when he appears, it sometimes pays to let him hang around a bit. Not that his help is likely to win success however - Romik's Caterpiller wins the award for 'toughest centipede clone' hands down. Firstly, the strawberry layer seems to be at work almost constantly which means you cannot progress at all by trying to clear areas because they immediately get filled up. Feeding in to this is the fact that it is very very difficult to position your laser base with any precision. The slighest touch of a key and your base goes charging 18 pixels or so in that direction!

The other baddies, such as the bug-eyed head and the laying thing, also move at similar supersonic speeds. Playing this, you actually even want to slow down a non-expanded Electron! Practically all strategy is therefore out of the window, all you can do is hold down the fire key, try and get underneath the pede and hope for the best. You can move up and down but this is not quite the advantage it seems when you appreciate just how quickly the base of the screen clutters up with strawberries. Blasting the bug-eyed head is about the most satisfaction to be had - it lights up in a multicoloured bonus as it bites the dust! Also, the packaging-up of this version is actually the most impressive - all the design of opening screen, scoring screen and high score table are all neatly sown up together rather like an arcade machine before you put in your 10p. If the game were even slightly easier, it could be a contender for Bug Blaster's crown but, as it is, the code is more a measure of frustration than gaming pleasure.

Mastertronic were next to hit the scene with Spectipede, which I actually reviewed in EUG #55. Revisiting it now - to truly compare it with the array of "centipede" clones - and the code for the game proper is actually quite passable. Not the best version by far but it does include numerous options allowing you to tailor your game.

Get your head around the pointless define your own fire button feature and you'll find You can play in Mode 1 or Mode 5; at a fast, medium or slow speed; and with free chocolate truffles each time you complete a level if you wish [Surely you made that last bit up! - Ed]. The previous review made reference to a bug which actually only occurs when Spectipede is loaded onto a BBC, not an Electron and so it was probably a bit unfair to bang on about this earlier - particularly because the tape is clearly labelled 'Electron Version Only'.

The Fast level is impossible, but Medium and Slow give something of a challenge. The mushroom-layer is very lax and only seems to lay a new mushroom once in a blue moon, hence mushrooms in the playing area only increase in this version when you destroy a pede segment. The spider, worm and a strange-flying bird all provide the opportunity for bonus points. Really it's only the incredibly bad presentation that lets down Spectipede, with screens devoid of colour, no flushing of the keyboard buffer and long pauses for musical intros and outros the main culprits in the case why it ultimately must be regarded as in the bottom three clones.

Finally in this eccelectic look at the incarnations of the pede, we have Players' Killapede, surprisingly not arriving on-scene until 1990 (and in fact, one of the rarest tapes available for the Electron). This is another Mode 5 version, and seems to have actually been modelled on Bug Blaster. The font used for the text is the same, the mushrooms, in both the way they appear and are destroyed, are completely identical, and the control and manoeuvring is indistinguishable. However, there are subtle differences which remind you that this is in fact a wholly different game. Firstly, there is no spider to challenge you at the base of the screen. Instead, you are placed further up the screen and there are in fact mushrooms below you.

There are also some other strange quirks. The scorpion is instead a very impressively animated crawling worm. However, he never seems to ever poison any mushrooms, so exists purely to be shot for bonus points. At the base of the screen, you also occasionally see a snail, with whom you must not collide. He lays flowers wherever he goes. However, each time you take out the last piece of the Killapede, the screen sort of scrolls a few lines upwards, knocking these flowers off the bottom!

Perhaps the strangest quirk is that, without exception until now, variants of the "centipede" clone have tended to stick to the 'rules' of the arcade that the Centipede starts at the top of the screen and continues to the very bottom. If he reaches the bottom and you have been able to navigate upwards out of its way, he begins his way back up the screen, but other centipede segments also begin to appear descending from halfway down the screen, catching your laser base between a rock and a hard place and upping the difficulty level.

So the attack of the pede on the Electron really ends where it started. But before closing, there's still space to mention the very curious game Bugs by Virgin.

Although its screenshots make it look like yet another "centipede" variant, Bugs is actually a very different beast. This is almost a sort of 'What if the pede shattered immediately the game started?' idea. Whereas you still get a field full of mushrooms, a laser base and bugs attacking from the top of the screen, the bugs come down at you scatter-gun style. The snail no longer poisons mushrooms but actually makes a snail-trail which acts as a force-field your laser cannot get through, hence allowing the bugs further to free-fall before you can actually take them out... It's a concept that works remarkably well as a twist on an all-too-familiar format and is certainly worth a look if playing through six different "centipede" clones exhausts your appetite for the traditional joined-up beastie!