A look at how to play Pokemon Go and the danger that's arisen from it

CONCORD, Calif. (KGO) -- Over the weekend, the nation and Bay Area were invaded by a swarm of colorful, imaginary creatures called Pokemon and also swarms of players looking for them with their smartphones.

"You'll just see these groups of two to four people standing around staring at their phones," said Pokemon Go player Aneka Bean.

RELATED: Police warn about criminals using Pokemon Go to steal from users

To the naked eye, there's nothing there. But you'll see something very different if you look through the camera on your phone.

"You're able to see a Pokemon sitting on your shoulder," said Gamespot editor Justin Haywald. "Like, I'm gonna catch that Pokemon. I just see it right behind you."

Haywald took on the tough task of teaching me Pokemon Go, a game you play out in the real world.

"Like oh, so I got a couple balls, I got a couple items, you can just do that while you're walking," he said.

The object -- to catch those mythical creatures.

"A Pokemon just showed up and he's actually right, right over there," said Haywald.

There are hundreds of species. And they prefer different habitats.

RELATED: Can Pokemon Go be harmful to your health?

"So in a city, these kinds of Pokemon will appear," said Haywald while gesturing to his smartphone screen. "Whereas over here is a forest, there's a park."

One park was packed with players.

"Just looking for Pokemon to show up on their screens, and they're all kind of walking around like zombies," said Bean.

Face down in a virtual world, you may not notice dangers in the real world.

"The last thing we want is someone to get assaulted or robbed for their electronic, or for someone to just wander into traffic and get hit by a passing motorist who's not paying attention," said Concord Police Cpl. Chris Blakely.

It can get worse.

"You see these flower petals falling over here, that means someone released a lure," said Haywarld.

Near St. Louis, police arrested three teens they say lured Pokemon to attract players and rob them at gunpoint.

And in Wyoming, one woman was looking for water Pokemon, but found something else.

"I didn't know what to do, I was really scared," she said.

A law enforcement official says, "There was a dead body."

Police say to enjoy the game, but be aware of your surroundings.

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