Sequels can be tricky. For successful musicians, there's the difficult second album. For sportsmen, winning back-to-back titles is more than twice as hard. Only filmmakers seem less bothered - the sequel is usually written before the original's premiere.

When it came to creating Metal Gear Acid 2, the quickly-turned-around sequel to special forces anti-hero Snake's PSP debut, there were plenty of improvements to be made. And with a streamlined movement system, more effective melee fighting and an appealing graphic novel art-style, several boxes have been ticked.

Of course, you might suggest a turn-based, card-based action game was never sensible in the first place. And Konami might agree: it's also making its first proper Metal Gear PSP game.

Certainly, Metal Gear Acid 2 remains a game for the committed fan.

Snake (a clone of the original Solid Snake, for those still interested in his genes) is sent into a secret military-industrial complex where something nasty's going down.

Unlike the fluid environments you might be used to guiding Snake around on PlayStation, however, here movement through the top-down 3D levels is mapped to a fixed grid of tiles.

At the start of each mission, Snake is dealt six cards from a deck of around 30, you can select from a library of hundreds. These can be roughly split into movement and action cards. When you select a movement card, how far you can travel is indicated by the highlighting of tiles around Snake. You play the card, and then move him within the range set by the highlighted tiles.

You collect new cards as you progress through the level, as well as buying new packs with the credits you gain by completing missions. Most can be used to move around, or if the situation allows you can use them to do more interesting things. Obvious examples are weapons cards, but there are also support cards, which increase the amount of cards you can use per turn or improve your weapon's killing power.

Up to a dozen guards patrol each level, and you each take turns to play your cards – Snake working his way to the exit, the guards trying to stop him. A timing system based on the cost that is accumulated when each card is played decides the order in which onscreen characters get their go.

There are over 500 cards to collect in Metal Gear Acid 2, so you'll appreciate just how complex the game is. This is one of the biggest challenges, as you often feel like you're not in control since the six cards in your hand dictate exactly what you can do.

The game also suffers from frustrating design. Success too often comes from random events. One classic example is fire. When a character is set alight, they continue to lose health every turn, and during that time will transfer their affliction to any players they come into contact with. Combined with tightly constrained levels, this means you can wipe out huge numbers of enemy troops just by standing next to them.

There are some compensations, most notably in the mysterious figure of Venus, a mean-spirited killer in a skin-tight red leather suit with a bust to rival model Jordan's. Joining up with Snake so you get to control two characters simultaneously, she provides new tactical options.

You can also play using a gimmicky cardboard-box viewing system supplied with the game. You put this over the PSP and it conjures up the impression of real 3D – as well as a headache. We suggest you just use it to check out an occasional movie of the hundreds provided. You can also transfer data from the first Metal Gear Acid game, as well as some of the console versions too.

For diehard fans, Metal Gear Acid 2 is a dream come true. It's massive, with each mission having at least four replay options. There's also an Arena mode, where you can go head-to-head against previous Metal Gear bosses, and loads to collect, watch and unlock. There's a two-player adhoc wi-fi option too.

The rest of us are better off waiting for Metal Gear Solid: Special Ops.

Metal Gear Acid 2 is out now – click here to buy.