Metro (design language)
Microsoft Design Language (or MDL), previously known as Metro, is a design language created by Microsoft, and is based on flat design style. This design language is focused on typography and simplified icons, absence of clutter, increased content to chrome ratio ("content before chrome"), and basic geometric shapes.
Early examples of MDL principles can be found in Encarta 95 and MSN 2.0. The design language evolved in Windows Media Center and Zune and was formally introduced as Metro during the unveiling of Windows Phone 7 in 2010, after which it was incorporated into several of the company's other products, including the Xbox 360 system software and the Xbox One system software, Windows 8, Windows Phone, and Outlook.com. Before the "Microsoft design language" title became official, Microsoft executive Qi Lu referred to it as the modern UI design language in his MIXX conference keynote speech. According to Microsoft, "Metro" has always been a codename and was never meant as a final product, but news websites attribute this change to trademark issues.
Microsoft Design Language 2 (MDL2) was developed alongside Windows 10, making a number of adjustments. In 2017, Microsoft introduced the Fluent Design language which gradually replaced Metro in the years following.