Space is the blank canvas of the imagination. Nobody knows what's out there, and the universe is so cripplingly huge that nobody is ever likely to. What we pluck from the night sky to fill our fiction is pure fantasy, revealing more about us than the organisms that may or may not be populating distant planets.

It probably doesn't say much for our self-esteem, then, that whenever we dream up an alien life, it tries to kill us.

Galaga 3 is yet another pixel-perfect retro conversion, a first-generation child of Space Invaders with just enough tweaks to justify an existence in its own right. Placed at the helm of a sluggish and curiously vulnerable ship, your job is to destroy a battalion of enemy spacecraft to advance a level, then do it again, and again, and again.

Once in a while a Challenging Stage arrives, the object of which is to destroy all of the enemy spacecraft before they leave the screen. Some of the ships in these levels take several hits, and each successful shot causes a small part of a word to appear. Juggling these enemies with gunfire for long enough spells out the whole word, which in turn endows you with bonus points. But apart from this regular digression Galaga 3 is a steady climb up the linear slide of increasing difficulty until somebody calls it a day.

Galaga 3's most unusual feature is the fact that queen enemies carry Blaster Head fighter parts, which you can commander through the medium of strafing. This bestows you with a range of capabilities, including: Phalanx, a tractor beam with which you can destroy several enemies at once; Sidewinder, which enables you to control your missiles in line with your own movement; and Stardust, which turns enemy missiles into euphonious powder.

It all sounds horribly confrontational, doesn't it? However, if the sordid violence of space fiction is a depressing characteristic of the human imagination, the beauty of the action is cause for encouragement.

Multi-coloured stars glint in the background while enemy formations line up in ordered ranks that hover for a moment, unravel into swirling sorties, then return to their ordered ranks. It may be war, but the movement of the enemy craft is like a choreographed ribbon-dance.

Your own movement differs slightly from the usual pattern in that you can not only strafe from side to side, but creep to about halfway up the screen, making it possible to avoid the occasional winding enemy and, more significantly, enjoy the freedom of two axes rather than Space Invaders's one. Autofire isn't automatic, but you can revert to it by pressing '0', and given the difficulty of moving and firing you're bound to do exactly that.

A consciously retro title, Galaga 3's presentation fulfils its brief well. From the authentically chiming music, to the nostalgic font type at the top of the screen, the attention to detail and the evocation of simpler times is pitch-perfect.

The merit of reproducing simpler times is questionable, of course, but if retro is your thing then Galaga 3 won't disappoint.