Matias Duarte, Google's vice president of design, thinks Windows 10 is no better than Windows XP. How do we know this? Because Duarte was kind enough to tweet something to the effect earlier today, calling Microsoft's modern design barely a step up from the usability of Windows software from 2001.

It's unclear what set Duarte off. Perhaps it was the new Windows 10 trash can, which is, according to Duarte's flat design principles, a crime against humanity. Or maybe it was the subtle inconsistencies in Windows 10, such as the design language clashing between the Windows 10 settings panel or the Start menu and... well, icons like this:

It's quite the criticism coming from the father of Google's Material Design philosophy. Duarte is credited with revamping the look and feel of the company's Android operating system. Duarte wants users of technology to think of software in physical terms. And no, not the ugly, tacky way skeuomorphism invaded early smartphone design with faux-leather and illusions of depth, but the way software would exist if materialized in the world like paper.

The idea is most evident these days in Android 6.0 Marshmallow, where Google Now cards and app interface mechanisms are stacked like snipped up sheets of colored stationary. Material Design now informs every Google product, from Android Wear and Chrome to the experimental Inbox email app. Of course, Duarte owes some credit to what Microsoft first laid out with its "Metro" interface in the days of Windows 8 and Windows Phone, which took the bold plunge into flatness before both Apple and Google.

After setting off a design and usability firestorm on Twitter, Duarte clarified his comments in subsequent tweets. He doesn't mind how Windows 10 looks, he said, but rather how it works similarly to Windows XP. Duarte appears disappointed that Microsoft failed to push the software forward in his eyes.

Update at 6:30PM, Monday, November 2: Added further comment from Duarte's Twitter feed and clarified that his criticisms of Windows 10 were not directed at how it looks, but rather how it works.