[SAN FRANCISCO] Roland James Rodas sprang from bed near midnight to race outside and catch a nocturnal Pokemon.
Edith Duro interrupted dinner to pursue a nearby creature.
A player who identified himself only as Nick B. spent part of Tuesday on a quest to reach a "PokeStop" tucked away in San Francisco's posh Nob Hill.
"It was in someone's backyard basically," he said, as he and a friend hunted Pokemon in front of San Francisco City Hall.
"We had to climb through a car park to get close enough to it."
Since its release in the United States, Australia and New Zealand last week, the free Pokemon Go smartphone game that overlays play on the real world has triggered a craze tinged with obsession.
The app based on a Nintendo title that debuted 20 years ago was adapted to the mobile internet age by Niantic Labs, a company spun out of Google last year.
The game uses GPS and mapping capabilities in mobile phones to let players roam the real world to find "PokeStops" stocked with supplies and hunt cartoon monsters to capture and train for battles.
Players visit "gyms" where the creatures can be conditioned as combatants to seize such training facilities.
"I had heard of augmented reality games and never quite understood what that all meant until this game came out," Roxanne Cook told AFP on Monday while hunting Pokemon in a San Francisco park during her lunch break.
"I think it is fascinating; really interesting and fun." The popularity of Pokemon Go has overwhelmed servers used to host play, leaving players frustrated but seemingly undeterred.
App analytics company SensorTower estimates the game has already been downloaded 7.5 million times in the United States, and brings in US$1.6 million per day on Apple's iOS app store from sales of virtual items, the Techcrunch site reported.
Rodas, 23, spent the weekend hunting, training and fighting Pokemon, taking breaks only for food, sleep and to charge his phone.
"Everyone is playing," Mr Rodas said.
"I haven't hung out with my friends this much in a while. Every other day we are getting together just to walk around playing the game." Evidence of the craze is easy to spot. Hordes of people can be seen walking in circles or wandering, eyes riveted to smartphone screens.
Chatter ranges from shouted Pokemon sightings to consultations about where to recharge phone batteries.
They are hunting cartoon monsters called Pokemon that are overlaid on real world settings when viewed through cameras on phones.
Players swipe their fingers across phone screens to hit creatures with virtual balls used to capture monsters.
Bicyclists or cars will suddenly pull over near spots which, in the game, are PokeStops or gyms.
"It takes me longer to ride my bike to work now, because I stop at every PokeStop," said Ms Cook.
"I also take longer ways to where I need to go, just to have more stops along the way." Ms Cook, a mom, said that part of the game's appeal for her was "the thrill of the hunt" and the fun of capturing rare Pokemon.
She also enjoyed the social aspect of the game, getting people out into places such as parks to play and talk together.
"To be honest, it does feel a little bit weird being a grown man out here playing video games," Steven Kong, 33, said while hunting Pokemon in the San Francisco Civic Centere
A Twitter employee playing Pokemon Go while on a break from his job at the company's San Francisco headquarters advised hunting outside nearby luxury condos owned by rich techies.
They don't mind spending cash to buy the game's virtual "incense" that makes Pokemon come to a player instead of the other way around.
Many players said their connections to Pokemon stretch back to childhood.
"It is a bit nostalgic for us, and once it catches on, like anything that is viral, everyone else wants to see what it is about," Mr Kong said of the game's dizzying popularity.
Pokemon Go comes with warnings for players to remain aware of their surroundings.
Police have urged players not to venture into places that are dangerous or off-limits, and to watch out for criminals who may turn them from hunters to prey.
Many businesses have welcomed the craze, offering discounts or deals to visiting Pokemon Go players.
However, some venues in the US such as Washington's Holocaust Museum and Arlington National Cemetery are asking people to be respectful and refrain from gameplay there.
Concerns have also been raised about whether data collected about players and their whereabouts is being kept private and safe.
US Senator Al Franken on Tuesday set Niantic a letter asking for information regarding what it does with data gathered about players.