Apple CEO Tim Cook told customers the company is working on “great things” during China Mobile’s launch of the iPhone today. Cook, who autographed iPhones at China Mobile’s headquarters store in Beijing, was asked about bigger screens and flexible displays, according to Bloomberg. “We never talk about future things,” he said. “We have great things we are working on but we want to keep them secret. That way you will be so much happier when you see it.” A previous report noted Foxconn has already shipped more than 1 million iPhone 5s units to China Mobile. The carrier also started selling the iPhone 5c today.