Apple CEO Tim Cook described the company’s ironclad control over its mobile app store as the best way to serve and protect iPhone users, but faced tough questions about competition issues from a judge while testifying Friday about allegations that he oversees an illegal monopoly.

Apple’s top app store executive faced a barrage of documents lobbed by an Epic Games lawyer aiming to prove allegations that the iPhone maker has been gouging app makers as part of a scheme hatched by Apple’s late co-founder Steve Jobs.