Duael Invaders is a little bit like the video game equivalent of patting your head and rubbing your stomach. It takes an immense amount of concentration to master, but when everything clicks, it makes you feel like the greatest human being alive.

If you didn't pick up on the pun in the game's title, Duael Invaders is a retro sh'mup balanced around a really cool dual space-ship mechanic. In fact the idea is so simplistic, we're surprised no one has come up with it before. The premise is such: there's a space-ship on the right and left extremities of the screen. You control the left space-ship with the d-pad, and the right space-ship with the Triangle and X face buttons. In the middle of the screen are different coloured space-blob things. You need to control both space-ships to defeat the similarly coloured foes blipping up and down in the middle of the screen. It sounds really easy, but it's actually rock solid. At first anyway. Perhaps it's us, but our multi-tasking abilities don't stretch as far as playing two games of Space Invaders at once.

Stick with it though, and you slowly adapt to how the game wants you to play. We started out thinking it would be best to control both ships at the same time, but we're convinced this is actually impossible. The trick is to keep switching focus between the left and the right sides of the screen. And it really works much more naturally than it sounds. As you shoot from left to right, your eyes will be drawn to the space-ship positioned on the right of the screen, and vice versa. So it becomes a game of push and pull, as your eyes dart between each side of the screen.

It's a really cool mechanic, that helps pull your attention away from the simplicity of the actual game. Sure there are combos, multipliers and power-ups to collect, but at its very core Duael Invaders is little more than a Space Invaders clone with a fantastic twist. The graphics take a hit as part of its retro inspired style, but the game looks sharp and is complimented by a stellar soundtrack.

Given the nature of the gameplay, Duael Invaders scales well as a multiplayer game too. The game plays in exactly the same way in two-player, but the idea is that each player holds a specific side of the PSP (or DualShock on PS3) in order to participate in co-operative or versus game-types. In essence the only real thing that changes in multiplayer is the way the game calculates scores. Honestly, we preferred playing Duael Invaders in single-player, but we're not going to criticise the developers for including additional methods of play. The more the merrier, we say.

Conclusion

Duael Invaders isn't going to win everyone over. We imagine its tongue-twisting breed of gameplay we'll confuse impatient newcomers unwilling to adjust to the game's intricacies. Learn to play it though, and Duael Invaders will reward you with a really neat twist on the familiar Space Invaders formula.