Space Invaders: Infinity Gene

"It is not the strongest of the species that survives, nor the most intelligent. It is the one that is most adaptable to change." Charles Darwin.

The quotation that opens this, the latest reinvention of Taito's most venerable arcade classic, does more than establish the game's overarching theme of evolution. It's also justification. For the first time in 31 years, a game bearing the Space Invaders name allows players to move up and down the screen as well as across it. Orthodox gamers steady yourselves: this is the first of the series' defining rules to be broken by this plucky upstart of an iPhone game, but it's far from the last.

It's clear a selfish gene has driven its development, steering it with rare clarity and purpose, but also with a brazen disregard for tradition. Nothing is sacred. In addition to the 1x1-pixel pea-shooter of the original, you now have a clutch of different weapon types to choose from. The eponymous invaders no longer march down the screen in tidy, staccato-shuffle rows, but instead sweep around in hyperactive, Galaxian arcs. No more is the challenge one of everlasting survival, the experience is now broken down into distinct stages, each with a start, a middle, an end and its own high-score table.

So, through Darwin's words, Taito preempts any indignation. "Yeah, we messed with Space Invaders," they admit. "But don't get mad. This is the way of all life. Fail to adapt and the Game Over's eternal. You don't want that, do you?" By the end of this sucker punch of miniaturised wonder, the answer is an emphatic no. Space Invaders: Infinity Gene is the very best game for the iPhone. But, more significantly perhaps, it's also the very best Space Invaders. Considering its grandfather popularised not only the shoot-'em-up genre but also the very medium itself, that's no mean feat.

The game begins at the origin of the species, stage 'zero' wading back into videogaming's primordial soup to revisit the black and white blobs and dots that approximated alien invasion in 1978. After a few moments playing here - during which time you wonder if you accidentally downloaded the original by mistake - the first transformation takes place. The screen burns out in a blaze of white pixels, before time and space explodes back into glorious long-screen view, your ship broken from its x-axis restriction, the game lighting up with a bold exclamation: "The King of Games is Back!"

Of course, Infinity Gene's evolutions are far from revolutionary outside the context of Space Invaders. Shoot-'em-ups have allowed their players to move freely around vertically-aligned screens for decades, and the idea of weapon upgrades that fall from downed flying saucers is as old as videogame time. But Space Invaders has always been defined by what it doesn't do as much as by what it does. The recent Extreme makeovers for DS and PSP may have introduced Flashdance pinks and greens to its deep space, but, by locking ship movement to the bottom of the screen and maintaining the crablike advance motif of the invaders themselves, maintained consistency. By choosing to throw these staples out of the window, the question and challenge for Infinity Gene's designers has become: how can we make a canonical Space Invaders game that obeys none of its rules?