A thunderstorm is rolling towards Chicago’s Grant Park. The thousands of people gathered for the city’s third annual Pokémon Go Fest, already sodden after a day of drizzle and rain, are now being told to evacuate for fear of lightning strikes. But I need to take a snapshot of a Gastly in the Spooky Woods if I’m going to complete this year’s festival challenge and uncover a rare new Pokémon. And I don’t have a Gastly.

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Risking death by lightning, I jog towards the Spooky Woods.

My name is Dominic. I’m 52. I have two twentysomething children and a part-share in a Pulitzer prize. I read philosophy and listen to Stockhausen for fun. And I love Pokémon Go. I also hate myself for it: my boyfriend rolls his eyes when I play, my kids think it’s sad, and the colleagues who know about it probably secretly judge me.

It is my secret shame, but I am not alone.

Facebook Twitter Pinterest ‘It is my secret shame, but I am not alone.’ Photograph: Lucy Hewett/The Guardian

For those who have been hiding under a Bulbasaur, Pokémon Go is an augmented reality game where players, armed with their phones, collect Pokémon in the real world. The cute little creatures pop up on a map of your surroundings as you explore on foot, and you just have to catch them. At Pokéstops dotted around the world, you spin a disk (often tied to a local landmark) to receive the balls needed to catch Pokemon, as well as assorted presents (more balls, stardust, eggs that hatch into new creatures).

It’s a social game too – sort of. You can team up with other players to battle more powerful Pokémon at “gyms”, or swap Pokémon with your friends (that’s “friends” in the social media sense – in other words, not really your friends. Or are they? It’s complicated).

Before the storm in Chicago descends, I bump into an attractive middle-aged couple catching Pokémon in the park. The pair would look more at home sipping smoothies after pilates than stalking digital creatures with their phones. When I get out my notebook, they exchange a look.

Facebook Twitter Pinterest Pokémon Go is a social game – sort of. Photograph: Lucy Hewett/The Guardian

Facebook Twitter Pinterest By the end of 2016, everyone was doing it: the app had been dowloaded 500m times. Photograph: Lucy Hewett/The Guardian

He is a sales director for a Fortune 500 company, and she runs a non-profit. They will only give me their Pokémon Go handles: Oceanna131450 and BeachBaby503. “We’re closeted,” she says. “Nobody at work knows I play.”

BeachBaby503 says their children got them into Pokémon Go when it launched in 2016. Their kids soon stopped playing, but they never have. They are both level 40, the highest level in the game (I am a 36.) Oceanna131450 hit 40 in year one and has walked 6,234km in the game – roughly the distance between Chicago and Panama. “We’re very goal-oriented,” he laughs.

I, too, have been playing Pokémon Go since the app was launched. In the beginning, I hid my obsession in plain sight. Everyone was doing it: the app had been downloaded 500m times by the end of the year. Celebrities had Pokémon fever, and even my co-workers were taking ironic snapshots of Pokémon at Trump rallies.

Then Hillary Clinton ruined it all, as she has so many things. “Pokémon Go to the polls!” she shouted at a rally in Ohio, ensuring Trump’s victory and ending the golden dawn of the Pokémon age.

The fad faded. But not for me – I went underground.

Three years on, I have walked 1,841km in Poké-land, or 1,144 miles. That’s the distance between New York City and Orlando, Florida. I have caught more than 11,000 Pokémon, flicking balls at critters in Stockport, Greater Manchester, and in Tokyo, Mexico City, Miami and Jackson, Mississippi. If I’ve been there, I have Pokémoned.

Facebook Twitter Pinterest ‘If I’ve been there, I have Pokémoned.’ Photograph: Lucy Hewett/The Guardian

I frequently sneak out to battle in raids to win rare Pokémon on street corners with equally furtive-looking strangers. Many players are my age – give or take 20 years. It’s never kids, and it’s always a mixed crowd: Latino construction workers, women in business suits, journalists. We gather on street corners, a secret society exchanging furtive nods and tips, waiting for the battle to begin.

“Psst. There are Snorlax in Bryant Park.”

“You wanna trade a shiny?”

Then we hammer away at our phones for a few moments before dispersing. Most often, we don’t exchange a word.

So what could explain this passion? It’s a question I’ve often asked myself, and I have theories.

First, there’s BF Skinner. Skinner, an American psychologist, developed the concept of “operant conditioning”, which shows how rewards and punishments modify behaviour. While Skinner had pigeons and rats pecking at buttons for food for his experiments, I am checking my phone for virtual rewards. A lot of the time I don’t get what I want, and this, it turns out, feeds my addiction. Subjects (pigeons, rats, me) tire of a task if they always get what they want. If it’s more hit and miss, they stay interested.

Skinner’s research helps explain why we still keep looking at Facebook, Instagram, our increasingly unmanageable emails. We are looking for that hit again amid all those yawn-inducing misses.

Operant conditioning, however, can’t take all the blame. I have been hooked on other apps: Words With Friends, Draw With Friends, Dots, all the way back to Snake. But in every case, my devotion soon died. Why does Pokémon still have my heart?

Facebook Twitter Pinterest ‘Why does Pokémon still have my heart?’ Photograph: Lucy Hewett/The Guardian

Enter Guy Debord, my favorite French Marxist theorist and founding member of the Situationist International. Debord’s most famous 1967 work, Society of the Spectacle, foresaw a new era of capitalism where the masses would be pacified and distracted by “the spectacle” – the reduction of our lives to a never-ending and all-consuming stream of media, images and messages. Sacré bleu! Was he ever right.

To disrupt the spectacle, the Situationists had a tool called dérive, a sort of unstructured urban wandering that allowed people to reclaim the landscape for their own purposes.

Pokémon Go isn’t quite what Debord had in mind, but when I play in a shopping mall, an airport, a museum, or in the line at the DMV, those landscapes are being repurposed. A new layer is imposed on top of the prescribed one, the map is redrawn, functions are subverted. I turn left when I should go right, north when I should go south, just to explore a new part of the city. Pokémon gives me an excuse to wander.

Which is why, back at Chicago’s Pokémon Go Fest, I find myself in a field risking my life for a Gastly, hoping to find the true reason behind my Pokémon addiction.

Facebook Twitter Pinterest ‘Those landscapes are being repurposed.’ Photograph: Lucy Hewett/The Guardian

Over the three-day event, 60,000 people gathered in the magnificent surroundings of Grant Park, walking 290,000km and catching 15m Pokémon. Pretty impressive for a fad that has supposedly fizzled.

The park was divided into zones. You can catch ice-type Pokémon in the Winter Forest (fitted out with snow machines and mini mountains), ghost types like my missing Gastly were in the Spooky Woods (where cobwebs hung from the trees), while others were hiding in the Fairy Garden, or the Sandy Desert.

The crowd has to be the most mixed event group I have ever seen. There are kids, but they don’t seem to be playing (it costs $25 to play at the event and they were just along for the ride). There are black, white, Asian and Hispanic Pokémon hunters. Some of the older ones are in motorized wheelchairs. It’s about a 50-50 split between men and women. Everyone is staring at their phones, but when I interrupt them, they couldn’t be nicer. As the rain starts, I shelter under a tree. “Do you want a rain poncho? I brought spares,” says the woman standing next to me.

A healthcare worker called Tyler Spence rushes over to help when he sees me taking a selfie. “You want me to take that?” he asks. He drove seven hours from Minnesota to get here. When I ask him about Poké-shame, he gets it. “People laugh. They say you: can’t possibly still be playing that?” he says. He doesn’t care. Spence has traveled the US making new friends and playing Pokémon. “I enjoy it for me,” he says.

Facebook Twitter Pinterest ‘I enjoy it for me.’ Photograph: Lucy Hewett/The Guardian

Facebook Twitter Pinterest ‘People are like: are you for real?’ Photograph: Lucy Hewett/The Guardian

Arnulfo Guevara, 35, drove from Los Angeles with five friends. They took turns driving and only stopped for food and rest breaks, setting off at 7pm on Wednesday and arriving at 3am Friday.

With his triple-pierced lip and chic rain poncho, Guevara looks like he should be sipping organic yerba mate in some downtown hipster joint. “I get teased a lot,” he says, tapping away at his phone with his beautifully manicured neon orange nails. “People are like, are you for real?”

By the end of the day, my shame is ebbing. Pokémon people are lovely. Many (but far from all) seem shy and introverted. They are together but separate, their interactions mediated by the game, but their friendship and kindness are real.

Still, I can’t escape the feeling that all this is really, desperately, sad.

The night before my day at the Fest I was invited out for dinner by gay Pokémon friends who had already had their day in the park. There are a lot of gay people playing Pokémon. Over pad thai in Boystown, TylerandJohn2 tells me there are a load of the exclusive symbol-shaped Unowns in the park. Then he drops a bombshell. Apparently if you collect them all, he says, they spell: ‘Wake up!

I can’t stop thinking about it. Whenever I see an Unown, the doubt comes back again. The spectacle has me in its thrall. What the hell am I doing? I should have downloaded Duolingo and learned Spanish instead. Wake up!

The next day, my self-loathing has dissipated again. I am having fun strolling in the park, chatting, catching Pokémon. Oh look, a Pachirisu! A snow white and baby blue electric squirrel with a spiky tail. So cute!

Back at Spooky Woods, as the speaker system warns us all to leave or risk electrocution, I manage to bag a Gastly, take my snapshot and complete the next stage of my task – allowing me to catch a rare Pokémon exclusively released at the Fest. When the storm passes, I finish the quest and am rewarded with a Jirachi, a flying “wish-making” Mythical Pokémon.

Facebook Twitter Pinterest ‘I can’t escape the feeling that this is desperately sad.’ Photograph: Lucy Hewett/The Guardian

Again, the self-doubt creeps back. It stares at me with huge dead black eyes.

I sink back into self-loathing, so I slope off to the Art Institute of Chicago, hoping high culture will detox my brain. Twenty minutes later, I have the app open again. There are Pokéstops all over the museum. There’s even one at Grant Wood’s American Gothic, one of America’s most sacred paintings.

I spin the image of their dour, judgey midwestern faces and Pokéballs come wheeling out. I actually LOL, IRL. Why beat myself up for having fun? You know what, American Gothic? YOU wake up! Poké 4 Life.