Series 40, or S40, was a software platform and user interface (UI) on Nokia's broad range of mid-tier feature phones, as well as on some of the Vertu line of luxury phones. It was one of the world's most widely used mobile phone platforms.[158] On 25 January 2012, Nokia announced that the company had sold over 1.5 billion Series 40 devices.[159] Although S40 has more features than the Series 30 platform, it was not used for smartphones, where Nokia primarily used Windows Phone and, until 2012, Symbian.