A player poses for photos during Pokemon Go Fest at Grant Park in Chicago, the United States, on July 16, 2019. Mobile game developer Niantic held the four-day Pokemon Go Fest in Chicago from Thursday to Sunday, with thousands of players attending the event to mark the three-year anniversary of the product launch. (Photo: Xinhua)

Players pose for photos during Pokemon Go Fest at Grant Park in Chicago, the United States, on July 16, 2019. Mobile game developer Niantic held the four-day Pokemon Go Fest in Chicago from Thursday to Sunday, with thousands of players attending the event to mark the three-year anniversary of the product launch. (Photo: Xinhua)

Players attend Pokemon Go Fest at Grant Park in Chicago, the United States, on July 16, 2019. Mobile game developer Niantic held the four-day Pokemon Go Fest in Chicago from Thursday to Sunday, with thousands of players attending the event to mark the three-year anniversary of the product launch. (Photo: Xinhua)

Players attend Pokemon Go Fest at Grant Park in Chicago, the United States, on July 16, 2019. Mobile game developer Niantic held the four-day Pokemon Go Fest in Chicago from Thursday to Sunday, with thousands of players attending the event to mark the three-year anniversary of the product launch. (Photo: Xinhua)

Players attend Pokemon Go Fest at Grant Park in Chicago, the United States, on July 16, 2019. Mobile game developer Niantic held the four-day Pokemon Go Fest in Chicago from Thursday to Sunday, with thousands of players attending the event to mark the three-year anniversary of the product launch. (Photo: Xinhua)