Players have been enjoying Nintendo’s Pokemon franchise for over 20 years, but for most of the history of the hit game series, catching ’em all has been a stationary activity.

With the exception of a pedometer called the Pokéwalker, designed to be used exclusively with Pokémon HeartGold and SoulSilver, all the in-game adventuring has required real-life players to stand still.

All that changed with Pokemon Go, Nintendo’s new free-to-play mobile game. Pokemon Go is an alternate reality game, or ARG; players move around a virtual map of their city, interacting with landmarks and catching monsters in the wild, by moving around in the real world. The more you walk, the more rewards you get: travelling around a city helps you find rare Pokemon, hatch eggs, and meet up with other players at real life locations to battle for control of a neighborhood. While ARGs have been around for years, nostalgia for the Pokemon brand has brought an unprecedented number of users to the game. So many players tried to join in the first few days that the game’s servers were flooded.

That means that players can’t be couch-bound: to win, you have to get up and walk (while it’s possible to drive between locations, certain features only work at walking speed). Reports are already pouring in about the health benefits of the game: a day of playing Pokemon means a day of getting exercise. For players with mental illnesses that make it difficult to leave home, catching Pokemon can be an extra incentive to go outside and interact with new people. The app places many Pokemon in parks and other natural spaces, giving players an incentive to get out and interact with nature–a proven mood booster according to researchers.

Of course, any game that encourages players to walk around while looking at their phones comes with the risk of accidents and other incidents. The Washington State Department of Transportation had to remind drivers not to play the game while driving a car. In Missouri, a group of criminals used the game to lure players to a site and rob them; in Wyoming, a teenager stumbled across a drowned body while trying to catch water-type Pokemon near a river. And police officers around the world have been trying to keep players out of areas where they aren’t welcome, including closed fishing piers, restricted areas of hospitals, private businesses, and even their own police stations.

 

Please stay off the fishing pier. The Pokemon will hopefully be there when it reopens. Had calls about this already pic.twitter.com/KtnarsXPaE

— Edmonds Police (@EdmondsPolice) July 10, 2016

Plenty of seagull sightings, but show of hands: Any #PokemonGo sightings on a ferry? @PokemonGoNews @PokemonGoSea pic.twitter.com/bodrQG0Imm

— WA State Ferries (@wsferries) July 8, 2016

If your weekend includes looking for #Eevee on #PokemonGO, please do so safely. No Pokemoning from behind the wheel. pic.twitter.com/Kt9CmTOKiP

— Washington State DOT (@wsdot) July 8, 2016

I’m telling ya, people really are driving while #Pokemoning. It’s no joke! #Pikachu can wait, people! https://t.co/1Ak2xWZRVj

— Washington State DOT (@wsdot) July 11, 2016