"Fluuuffy Sheeepy!" drones the eighties synth-box voice as, two minutes into the current level, I collect my 12th upgrade-sheep. The frequent repetition has me parroting the voice after the event, trying to perfect the tone and timbre. But this is no time to pause and feel daft. I'm way too busy strafing waves of procedurally generated sprites with artful, calligraphic sprays of fire from my ship's cannons. Gridrunner Revolution keeps you so very busy manipulating its physical laws and countering the varied approaches of its baddies, you can't really give the infectious ambient soundscape your undivided attention - you just have to sit there and let it do things to you. This is precisely the effect developer Jeff Minter wants to create. And in this case, the result is gently if pleasingly embarrassing.
As shoot-'em-ups go, Gridrunner Revolution will seem familiar from the outset. Move ship around playfield, rotate ship to shoot in any direction, fire a constant, liquid stream of death at the enemy, grab upgrades. For the long of memory, it's clearly a vintage Jeff Minter shooter (note recurring sheep motif). Regarding its relevance to the modern landscape though, it's hard not to draw comparisons with Geometry Wars. Originally a mini-game in Project Gotham Racing 2, and later one of the great success stories of Xbox Live Arcade, Geometry Wars really planted the flag for retro-shooters. But it was just that - a shooter. An incredibly pretty and incandescent and addictive and very, very polished shooter. And one which took many of its cues from Gridrunner++, Revolution's forerunner. Grid? Check. Crabby ship? Check. Retina-searing particulate explosions? You get the picture.
But there's a playful, experimental aspect to Revolution which shmups generally lack, and that's not a reference to its stylistic attributes... ruminant symbology and commendably insane voice-overs, for instance. It lies in the fabric of player choice, and the feedback loop the game provides you with. For example, you can happily play the entire thing simply shooting enemies, collecting upgrades and cracking levels, and you'd have a fairly good time. You don't even have to rotate your ship to succeed; with the advent of diagonal and rear-facing cannons, you're pretty much sorted. Playing the game like this would also be a tremendous waste of all that Gridrunner Revolution has to offer.
There are two key elements which turn it from a game into a playground: the first is gravitational hotspots. In every level, you'll find the sun floating lazily around the playfield. The sun has mass, and affects the trajectory of your fire - rather like the 'slingshot effect' in which satellites use a planet's gravitational field to gain momentum and alter course. The sun's mass bends the arcs of your weapon fire, and at the simpler, early stages, means you can effectively fire around corners and hit enemies which aren't directly in front of you.