Photo: YouTube: The Official Pokemon Channel

Pokemon is a Nintendo game launched in the 1990s. In the Pokemon world, "trainers" travel the world to catch monsters of all shapes and sizes, called Pokemon. Then they use them to fight each other. It quickly became a TV series, movie, and merchandise franchise.

Now it has a new form – Pokemon Go – which combines the screen world and the outside world. The app for the game, downloaded free to Android and iOS, uses your phone’s GPS and clock to decide which Pokemon appear. You have to go to different places in the real world to catch different kinds of Pokemon.

There are also gyms, where you can fight gym leaders, and real-world locations called PokeStops, where players can meet. You can even buy things with real money to lure Pokemon to these stops.

It became instantly popular, and is likely to be more popular than Twitter very soon. For example, when two people set up a Pokemon Go event on Facebook, they expected it to attract a few friends. In fact, over 5000 people responded, and another 13,000 people showed an interest.

Another example of its popularity is that its server crashed early last week, angering many players. At that time, the game had only been released in the USA, Australia and New Zealand. Some people think that UK players, trying to bypass servers to get into the Australian game, overloaded the server. The server was up again within a few hours.

Already, “nonplayers” have found ways to make money from the craze. Some people drive players around in their hunt for Pokemon, and a few businesses host “PokeStops”, offering discounts to customers who can produce certain types of Pokemon.

Not everyone is happy about the the game. There are reports of players glued to their mobile phones and injuring themselves by tripping and falling, or walking into trees or poles. Some have had minor incidents while driving.

A gang of four teens in the US state of Missouri used the game to lure nearly a dozen victims into armed robberies. They used the GPS feature of the app to find victims. One of the more unusual incidents was a girl in the state of Wyoming, who found a body under a bridge while looking for water Pokemon.

US Senator Al Franken expressed concern about the user data collected by the game, how the data is used, and who it was shared with.

A mother in Adelaide, SA, was worried when the app directed her to drive her 10-year-old son to a carpark which was often used by gay people to meet up. She pointed out that there was no way you could report a location as unsafe or risky for the app.