PixelJunk Shooter's great achievement is that, having come up with such a simple, novel and joyfully interactive concept, it doesn't stop there, and also doesn't break anything by iterating. Virtually every stage throws new ideas, substances and combinations at you. Clouds of rising gas only warm your ship slowly, but choke survivors, collect under ceilings and explode when they come into contact with magma. Sheets of ice freeze water, but can be melted away by magma or laser beams bounced off mirrors. Hot, magnetic oil surges towards your ship, gathers around switchable electro-magnets, fizzes magma into nothing and creates gas when brought into contact with water.
Enemies that release trails of ice or gas are brought into the mix, as well as power-up suits that allow your ship to release streams of magma or water and grapple chunks of land or ice, or that invert your magnetic polarity or heat sensitivity. PixelJunk Shooter is a constant conveyor-belt of fun toys and exciting domino-chain interactions. It's part retro videogame, part chemistry set; part Geometry Wars, part Zelda. Only rarely does it fully explore the potential of all these different elements, but to Q's credit, that's because each idea is hastily dispatched in favour of something new. Nothing in PixelJunk Shooter outstays its welcome, even the three clever boss battles.
That goes for the game itself. Shooter is very short, although not quite as brief as the first two-thirds would have you believe. Boss levels are unlocked by collecting gems, some of which are well-hidden under rock, in magma pools or in secret caves off the edge of the screen. You'll more than likely need to start backtracking through earlier levels to meet the requirement for the final boss - and having done that, you'll feel compelled to hunt them all down, find all the special survivors and score a perfect survival rate on each.
Shooter also features online leaderboards and a score-attack option, which actually just exposes the scoring system in an on-screen readout. Rather than kills, scoring is based on collection of survivors and coins, which are scattered around levels and dropped by enemies, and can be hoovered up quickly with a quick spin by rotating the right stick. These give you a bonus which is then depleted by time, so good score runs involve finding the optimum route through a stage and a balance of speed and completism. It works well enough, but the truth is that Shooter suits secret-hunting better than it does score-attack; its primary drivers are exploration and lateral thinking, not skill.
A simple, local two-player co-op mode is included which doesn't change the game much, and doesn't have the chaotically competitive edge of, say, New Super Mario Bros. Wii, lacking as it does independent score-tracking or friendly fire. But it does suit Shooter's style and level design extremely well, so it's more than welcome. You also get PSP remote play support, and PlayStation Home unlocks to go with the fairly attainable Trophies.
PixelJunk Shooter is a taut, well-made and original game that's been lavished with good design and slick coding. It won't detain you long - and without giving too much away, the post-credits kill-screen suggests a DLC expansion is highly likely, as does PixelJunk's past history. But for every minute of those few hours, it's an unpredictable, fluidly entertaining blast.