It's Tuesday afternoon in a quiet suburban Christchurch park. Two small boys throw themselves down a slide, their blonde hair billowing as they race to the bottom, arms flailing Kermit fashion.

Saphire MacManus looks up from her phone while rocking a toddler in a pram. It's an everyday scene but the world around you is not always what it seems.

The mother of three is secretly at war.

NIANTICPROJECT/YouTube An ad for Niantic Lab's online/real life game Ingress.

"Someone is trying to take over my park," says the 29-year-old.

She looks furtively over her shoulder. Is it the man sitting in the nearby blue Honda Civic? She can't see a phone in his hand.

"But someone is here," she says knowingly. "They're hacking my portal."

Gavin Treadgold Ingress players from around New Zealand met up in Christchurch on September 19 for a rare event which saw the ''Enlightened'' (green) and ''Resistance'' (blue) teams join forces.

MacManus is playing Ingress, an intriguing worldwide multi-player augmented-reality game created by Google and Niantic labs.

This is all happening right now where you live.

The premise of the game is that a mysterious energy - "XM" - has been released. To find these energy sources, you actually have to go outside and walk around. The twist is that the game world of Ingress is actually layered on top of the real world.

VICKI ANDERSON/FAIRFAX NZ A map of Christchurch showing people playing Ingress and which parts of the city are captured by the Enlightened (green) team and the Resistance (blue) team.

In Ingress the future of the world is at stake. You must choose a side.

You can join the Enlightened, the green team, who, as the original story goes, believe aliens are using the portals to transcend humanity to a higher state; or the Resistance, the blue team, who prefer that such a scenario didn't happen.

In Christchurch, people using nom de plumes like " Biopiper " and "Shadowman 1994" wage battles over portals such as the Christ Church Cathedral, the Chalice, graffiti art and among the floral displays in the Botanic Gardens.

Have you ever seen a picture of a pukeko on a lamppost and wondered why it was there? They are also Ingress portals.

Anyone can submit a portal, you just take a picture of the location, type out a brief description and send it away for approval. You might have to wait a while, however. There are only 12 people worldwide approving portals and they are currently working through around a million submissions.

Participants download the Ingress app for free, then use their phones to log into an augmented version of Google Maps and use GPS to navigate to portals - landmarks, murals, buildings and other interesting sites or sculptures – that the game's two factions must fight to control.

You can only capture a portal by visiting the physical spaces where it appears on the map.

When a player is near a portal, they can "hack it", turning it from blue to green, or vice versa, and set up defences before linking it together with the rest of their chosen side's territory.

"You have to make a field, basically it's a triangle," MacManus explains. "There are a lot of triangles in Ingress."

This struggle to save the planet spans the world.

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Since its launch in the United States three years ago, millions of people have signed up to fight the unseen war.

In New Zealand thousands of people play it and in Christchurch hundreds of residents quietly go about their daily lives battling over local landmarks.

Resistance member MacManus says she doesn't follow the back story of the game - "something to do with aliens" - she just likes to do the missions.

"I like taking other people's portals, I like fighting. I like owning a certain area," she says.

She began playing Ingress shortly after her husband, Mark, started it around 14 months ago.

"I got sick of Mark wandering out by himself when we went on family outings. We'd go to the Botanic Gardens and the kids would ditch me and he would be off with his phone doing little missions and I would be left there by myself," she says. "Now it's our thing we do together with the kids, our eldest son likes doing hacks too."

MacManus laughs as she describes it as a "build and destroy game".

"Perfect for Christchurch."

To play, participants must be close to a portal. They then press a button which says "hack" and, if successful, they turn the portal from blue to green or vice versa.

There's a social aspect too.

Participants chat online and often meet up for " beergressing " or " cafegressing ".

In Christchurch's central business district portals are everywhere.

"The inner city is the best place to level up," MacManus says. "Everything from signs in Hagley Park to the Chalice, graffiti art, and even the bike rack at 2 Degrees are portals. There's no end to it."

For MacManus and family the biggest benefit is seeing Christchurch through "new eyes" and discovering interesting places in the city that they had previously not been aware of.

"We have discovered heaps of cool places and parks to take the kids to," she says. "It's something which gets us out exploring the city together as a family."

It's a sentiment echoed often by other players.

Ingress attracts people who are not stereotypical gamers - retired couples, families and people of all ages from all walks of life.

Gavin Treadgold says that playing Ingress has "changed his life".

A member of the Resistance team, he started playing in November 2012 and was the 17th person in the world to reach level 16, the top tier of the game. Every day he plays as often as he can, and it has changed the way he sees post-quake Christchurch.

There have been more personal benefits, too.

"I was previously a sedentary office worker, most of the work I did was sitting at a desk," Treadgold says. "Because Ingress involves a lot of repetition, you have to walk to navigate to the portals, I built an exercise routine around it. I would find myself going back to the same cluster of portals and I'd walk four laps around the park and suddenly I was getting exercise. I peaked at about 106kg three years ago but now I'm steady at below 90kg. I've lost a fair amount of weight from it."

He describes Ingress as "gamifying exercise".

"It encourages you to exercise and rewards you with the medals. In the next few weeks I'll chalk up 6000km just playing the game."

When he has been battling depression, he credits getting out of the house to "blast a few portals" as helping to lift his mood.

"I have done a fair bit of geocaching but Ingress is quite a different game from others," he says. "I have certainly had depression over the years and some of the things that help you counter it is exercise and getting outside in the sunshine."

Ingress attracts a wide range of people from all walks of life but is skewed towards those aged between their 20s and 40s he says.

"We have one of the oldest agents in New Zealand in Dunedin. I think he's 86 or 88 now. He has reached the top level of Ingress."

The game involves " Baf -ing" - which he particularly enjoys - and Treadgold has also combined the game with overseas travel.

" Baf -ing is creating big ass fields. I had a four week trip to the United States and went to Ingress events in Washington DC and Portland," he explains. "You use Ingress to walk around and discover historical sites and sculptures, I never ran out of things to see. I really like the exploration and discovery aspect."

Marlborough soap maker, Richard Peterson, 52, fights as a member of the Resistance "every day" with his partner, Jenny.

Last weekend the pair travelled to Christchurch to take part in a rare Ingress anomaly event.

"In March we were in Christchurch for a massive anomaly that was an all-out, no-holds barred war that most of the population missed," says Peterson. "The one last weekend was different, it was a Teal baf ."

From around New Zealand members of the "greens and blues" travelled to Christchurch last weekend to join together to fight over 50 portals at a time.

"It was happening at multiple places around the world," he says. "We had 200-300 people in Christchurch but at the same time 5000 people were playing it in Japan."

A rare collaboration between the warring factions, in New Zealand the main event was held in Akaroa while similar teams joined together across the Tasman in Byron Bay and Tasmania.

"We combined to make multi-level fields, teal fields, with blue and green overlapping each other."

The purpose?

"Because we could. We were pretty sure it was the first one in the world which crossed national boundaries, a huge distance from Akaroa to Byron Bay. We had enough high level players together to get the links."

He and Jenny play individually and together, he says. If he's running children to sports events he plays it.

"They're teenagers now but I wish we'd had it when the kids were little. You visit places you'd never imagine," Peterson says. "The other reason is exercise - I've heard a cardiologist say that everyone should play this game and go to places. A lot of walking is involved."

Christchurch truck driver AJ McLachlan regularly devises missions for Ingress players.

He created last weekend's Teal anomaly event over the course of two months. It was a particularly special event.

Anomalies don't happen very often, he says, and require "months" of organisation .

"That was my op, I came up with a plan to put a combined field from blue and green, Teal, from here to Australia. It hadn't been done before between two countries," he says from Nelson, having just stepped off a truck.

McLachlan started playing Ingress with his partner Heather in mid-February.

"I am blue through and through. There are different aspects of Ingress but I like the technical aspect of creating big fields, that's what challenges me."

He helped set up a group which sees members from the blue and green teams work together.

"In the end we are just playing a game and we are all normal people. The South Island Resistance seemed quite hard core against the Enlightened and that wasn't how we wanted to play the game."

For the first six months he and Heather were "super" competitive.

"It got to the point where it caused an issue between us. We were always racing each other to the next level, who would level up first. At one point it stopped being fun."

They sat down and talked about their Ingress addiction and resolved it.

"I proposed to Heather about 15 minutes before the operation started in Christchurch last Saturday," he says. "She said yes."

Who is winning the battle in New Zealand?

"Southland and Dunedin is green as is Nelson, we're winning in Marlborough, Christchurch keeps swinging back and forth from blue to green. The West Coast is transient, there are one or two strong players who do some huge kilometres," Peterson says.

"Wellington is unusual, the parliament end of town is blue dominant, Aro Valley is green."

Often, when he's been playing for a while, Peterson says looks up and expects to see green or blue in front of him in the real world.

"I heard that 12 million people worldwide are playing it, it's everywhere," Peterson says. "My 75-year-old mother in law plays it. There's computer geeks, pensioners, young mums, all sorts."

Cherie Ewart owns a significant chunk of Halswell as a member of the Enlightened team.

The mother of two discovered Ingress during a difficult pregnancy.

"It's funny that a game can do so much," she says. "I gave up work when I was 7 months pregnant with my youngest, she is eight months old now. I was having bad cramps. The only exercise for the last part of my pregnancy was Ingress. It helped me get up off the couch."

Within a five minute walk of Ewart's house there are about "100 portals".

"Quite often I walk around the Halswell quarry. What would be a half hour walk turns into an hour and a half with Ingress. I don't play as much as I used to but it's very hard to put down."

As a stay-at-home mum, she enjoys the social aspect of Ingress whether it's communicating online in the team chatrooms on Google or Slack or chatting to other players she meets at portals.

"I like to have a green field over my house at all times. I like getting up and seeing that it's green and not blue."

It's a game you can't win, she says, but she tries to win a cycle of the game and notch up regional scores.

"That's your weekly win... battling for portals in your area."

Lyttelton is blue, so is Sumner and Papanui but Merivale is green.

"I live in Halswell and I have friends who live in Wigram and Church Corner so between us we seem to be able to keep the field up over that whole area quite well," Ewart says.

"There are portals at places like Mount Hutt. We went up for a day in the snow just to keep the portal up."

A portal in Fiordland cannot be accessed by cellphone so intrepid players of Ingress take signal boosters and a wi-fi repeater to hack it.

"It gets a bit technical with some of the unique hacks. Stewart Island has quite a few portals, too, but no-one who lives there plays it. The people who made Ingress have announced a new game coming next year which involves catching Pokemons in real life, the video has quickly got something like 12 million views. We've noticed a huge jump in people playing Ingress because of it."

Ewart admits that some people take their obsession with the game a bit too far.

"You do have some possessive players who say 'that's my area', as soon as you smash a portal they go out and recapture it," she says.

MacManus agrees.