Microsoft continues to add a few more innovations and special features for the forthcoming “GOLD” copy that will debut on July 29th

Microsoft surprised testers of Windows 10 on Tuesday by launching build 10159 of its forthcoming operating system, just a day after the last update. Gabe Aul, an engineering general manager at Microsoft who serves as the public face of the Windows Insider Program, announced in a blog post that the company released the new build to testers in the program’s Fast ring.

Unlike yesterday’s build 10158, the latest build doesn’t bring that many new features. Instead, wrote Aul, it’s packed with more than 300 bug fixes, along with a mysterious “very interesting change.”  According to a report by Neowin, the change in question is a redesign of the login screen that puts a user’s photo front and center in a translucent pane over their desktop picture. It’s a marked difference from the previous iteration of the login screen, which placed a user’s photo to one side of their name, Microsoft account email and password field.