We have been playing State of Decay for over 10 hours now. Actually, ‘playing’ might not be the most accurate description for what we have been doing in Trumball Valley, the harrowing, ominous world Undead Labs have squeezed into their first Xbox Live release. No, we have been surviving. Surviving on a few snacks here and a few meds there. We have lost friends and acquaintances on a daily basis. We have fortified our defences only to see them breached by relentless, rotting flesh-eating bastards. And still they keep coming.

If you allow yourself to become immersed in the world Undead Labs have created, you are soon rewarded with one of the more remarkable recent releases through Xbox Live (a PC version remains in development). This is not a pick-up-and-play arcade romp. No, it is a full-on zombie survival simulator. It is a chance for anyone who has dismissed the survival methods on show in Night of the Living Dead, The Walking Dead or any other on-screen zombie invasion with ‘dead’ in its title to put their neck on the line to see if they do actually have what it takes to remain unscathed for more than five minutes when all around them are being chomped on by packs of hungry zeds.

Right from the off you are dropped in the deep end, unsure about what is happening as Trumball Valley goes crazy around you. With the loosest of handholding you are guided to relative safety and then you and a small bunch of survivors are pretty much left to get on with things.

You can expand your group by finding new enclaves beyond the sanctuary of your makeshift home. Gaining people’s trust enables you to become friends, and once this is achieved new friends become a playable characters. It is essential to have multiple characters to switch between in order to give others with injuries and fatigue the chance to get some well-earned R&R.

Having more people in your community will increase your chances of survival, but bring with them the need to feed and keep healthy, while also managing their skills and temperaments. When you are not playing as a selectable character, they will still play a part in your game. Sometimes they will get fearful and need a pep talk. So it falls to you to take them beyond the safe confines of home to whack a few zombies, have a word in their ear and get their confidence back up. Unhappy campers leave your base prone to more issues, the last thing you need when slavering zombies are gathering outside your home.

Character’s skills can be improved to make them stronger, with experience gained through performing certain actions and completing missions. These might range from running trades with other enclaves or rescuing one of your own from the rotting clutches of a hungry horde. Each playable character also carries a rucksack and a journal, the latter being an essential tool. With a press of the d-pad you can access your journal allowing you to manage your inventory, see the status of others within your group and check current skill progression.

But these options barely scratch the surface. There is a great amount of depth to State of Decay, with there being a lot of mechanics that you will only happen across hours into the game, often by chance. As said already, there is no handholding here. Or rather, there is for a fraction of the way across the road then you are left to run terrified the rest of the way across like a startled Jiff Ramsey. For the most part the sense of discovery is quite refreshing, but some of the game’s more useful features might go unnoticed if you don’t approach the game with more than a bit of curiosity. For instance, through your home’s radio tower you are able to radio for the locations of food, materials and survivors, all essential to the prolonged preservation of your community.

Venturing out into the world to scout locations and retrieve such supplies is a tense experience. Once you enter a building, and pretty much every building in the game can be looted, you have the option to perform a slow, quiet search or scour quickly, but noisily, and risk alerting the undead to your whereabouts. This is a delicate game of risk and reward and can make for some frantic runs around town looking for essentials. All of which are in limited supply and require careful management. Not enough meds? People will get sick and put your camp in jeopardy. Rely on a melee weapon for too long and you risk it disintegrating in your hands during a fight. The amount you can carry is also limited by weight and the size of your rucksack. Being encumbered will drain your stamina more quickly and turn the outrunning of zeds into a race as unbalanced as a toddler versus Usain Bolt.

Trumball Valley is a fairly picturesque place, once you look beyond the slight blemish caused by reanimated corpses shuffling around it of course. It is also a large area. It is perfectly feasible to spend your first few hours with the game nestled in one corner of the map. And why not when venturing any further prompts a feeling of complete isolation? This is not a relaxing game, nor is it one that is easy to put down. Just when you are ready to switch off and go and do something more restful like tickling tiger sharks or pulling a boat through a jungle, the game teases you with a new mission. A survivor needs your help! And look, they are not that far away. C’mon, it will be easy peasy lemon squeezy, just grab some more ammo and get going. You never know, these guys might have food. What’s the worst that could happen? Being ripped in half by a pack of zombies is one answer to that particularly question. Rest in peace, Felix, your memory will live on.

And the grim reaper will come for you. Every death in State of Decay is permanent so when you lose characters to zombies the sense of loss is palpable. It hurts. Here is one of the game’s great successes, and the standout gameplay mechanic that gives State of Decay its edge. Knowing that any foray into town can end in tragedy lends a real sense of jeopardy to each venture beyond the walls of your camp. It also means finding a balance between the characters you switch between is essential. Rarely has a sense of only being as strong as your weakest link been so well realised as you juggle between the survivors you use to ensure an even progression of skills and a greater hope of making it through another day and night unscathed.

In a world overrun with the undead money is no longer a commodity. Instead players gain influence as a result of their actions. More influence means a greater freedom to utilise supplies, in turn enhancing the likelihood of success during a mission. Earning influence involves, to use the game’s own parlance, “getting shit done.” This no frills, direct approach is indicative of a whole, and gets to the root of what makes State of Decay so enjoyable. Should the world ever become plagued with zombies there would not be a manual. You would have to grab what you could carry and set out to survive for as long as possible.

To naysayers, this might sound like making excuses for an oversight. Maybe the game should be clearer in places but we prefer to give Undead Labs the benefit of the doubt and think a sense of helplessness is an intentional aspect of the game’s design and a way to plunge players straight into the action and get them thinking for themselves as much as possible.

That is not to say there are not other more valid issues with the game. There’s no getting away from the fact State of Decay is slightly rotten around the edges. Characters will often glitch through otherwise solid objects (arggh, door zombies!) and we once drove around town with a zombie walking on the spot, the spot being the bonnet of our car. So far, so comical. At the more frustrating end of the scale we had a SWAT team, supposedly along for assistance, do little else besides stand dumbly in a doorway blocking our exit for a good few minutes. Then they were called away, presumably to stand still on a high street pavement 10 minutes before the shops close on Christmas Eve or to wear a top hat in their local cinema.

The slim story rarely moves beyond generic but this is not really an issue when every player has the potential to create their own plot, their own tale of how they navigated the game world and survived one day longer. Being able to share these experiences in a co-op would have elevated State of Decay to near-legendary status.

At least the AI within the game is robust enough to leave you feeling like you are not completely alone (as long as your companions are not dressed in SWAT fatigues). Many missions are solo affairs but when you do have others along for the ride, such as for clearing infestations, they more than prove their worth, keeping lookout and actively getting stuck in whenever the undead swarm.

We are not even sure if the game is challenging or our frequent sense of panic means we would be first in line at the brain buffet if zombies ever did infest the world. In small groups the zeds are about as much use as a drunk on a surfboard but in hordes they are lethal killing squads and will quickly overpower reckless, panicked players. Apparently even zombies have social stigmas and certain ‘freak’ zeds including Juggernauts or Ferals can also be found bumbling around towns ready to dish out even quicker deaths than regular zeds.

As with all good games, State of Decay is an experience that filters into your everyday life. Not to the extent of checking every building in your neighbourhood for supplies or whacking shifty-looking pedestrians in the face with a cricket bat, but thoughts about missions and what to look for next will likely occupy your thoughts and have you itching to get back to Trumball when you are not there. While you are away the game will sim the rationing of meds, foods and other goods, so you never quite resume where you left off, heightening Trumball’s sense of reality.

This is a hulking beast, a deep, engaging experience and already one of the year’s standout titles. Xbox Live has offered gamers many gems since its inception and this is one of the more precious. We need to go now. Our watchman just spotted a horde heading our way and Alan is freaking out about nearby infestations. We hope we will see the sun rise again.