Some games are more fun when the odds are stacked heavily in your favour. Initial impressions will dupe you into thinking Laughing Jackal's latest PlayStation Mini is a puzzle game, but once you start to earn money and upgrade your equipment it becomes a much more chaotic experience.

Set in the City Of Redfield — someone's been playing Resident Evil! — OMG-Z puts you in control of a lone rifleman surrounded by zombies. The bad news is that you've only got a couple of bullets. The good news is that for, and we quote, "cool and unimportant" reasons, one carefully placed shot is all you need to clear out an entire screen of the undead.

OMG-Z's primary mechanic revolves around chain reactions. Shooting a zombie causes their body to explode, triggering any nearby corpses to splatter and so the chaos continues. There are different types of zombies, some have bigger trigger radiuses while others reduce to pools of acid on the floor. A third type of zombie — derived from soldiers and police officers — carries a weapon in hand and fires off ricocheting bullets when demised. The result is madness.

The crux of OMG-Z, therefore, revolves around picking off the right zombie to trigger maximum damage. A carefully placed bullet to the head of an exploding zombie can trigger gun-shots and cover the ground with deadly acid, trapping other undead and ultimately clearing the screen. It's a genuinely brilliant mechanic, that delivers each and every time the screen transforms into a satisfying shade of crimson.

But what starts out as a joyous mechanic only enhances as you progress. Reaching score quotas on each stage will award you with a medal and cash, which can then be spent on a variety of upgrades. These upgrades increase the blast radius caused by exploding zombies, and the number of bullets fired by soldier zombies. In short, they allow you to create even more chaos. Technically this should make the game easier, and it does to a degree, but Laughing Jackal's got the pacing just right — you always feel overpowered, but never to the degree where the gameplay loses its purpose; you still need to pick the right zombies to cause maximum damage.

The upgrade system also makes the game devilishly moreish. We found ourselves playing levels over-and-over to earn cash, only to play more levels to observe the implications of our expenditure.

Despite being impossible to put down, OMG-Z is perfectly segmented for a portable experience. Levels are broken down into an Outrun-esque pyramid, which introduces several "narrative paths" each culminating in a unique graphic novel ending. Naturally the story is almost meaningless, but at least there's some pay-off for your endeavours.

The game's visuals are probably its weakest element. It's easy to see what Laughing Jackal were going for — a minimalist, MadWorld-esque visual style — but the game ends up looking more like a broadsheet newspaper than anything else. With so few colours and such a big emphasis on black, white and red, the action can get muddled and unclear. It's not helped by microscopic fonts and undefined zombie sprites. Often the only way to tell between different zombie classes is by pressing the R button and getting a colour-coded view of the playing field. Laughing Jackal do deserve credit for fitting an outstanding number of moving parts on the screen at once though, with upwards of one hundred individual shuffling corpses filling the screen.

This can lead to some frame-rate issues during larger chain-reactions, but in a twisted way these stutters add to the chaotic nature of the action. It's awesome when you feel like you're pushing the game to breaking point by killing so many zombies with one shot.

Conclusion

With an enormous array of levels, plenty to unlock and a huge amount of replay value — the OCD amongst you will get hooked on unlocking each platinum trophy — OMG-Z is a real tour-de-force. It summarises everything that's great about Minis: accessibility and addictiveness. While a level can be enjoyed in under 20 seconds, there's enough content in OMG-Z to keep you going for several hours. Even better is the way Laughing Jackal's paced the game, making it difficult to stop playing once you begin.