Microsoft is positioning Windows 11 as a wholesale redesign of Windows itself, adding all sorts of flourishes and effects to the operating system. That puts some on edge, remembering the disaster of Windows Vista that resulted in sluggish performance, which Microsoft is looking to avoid with Windows 11.

Kevin Gallo, head of the Windows developer platform, participated in a Q&A session to explain some of the design decisions behind Mica and how it affects performance.

“Performance is really a top priority for us and we want to ensure that all these fun new functionalities are super fast and don’t impact the OS,” Gallo noted. “For example, Mica was specifically designed for higher performance when compared to things like Acrylic.”

The company’s Fluent Design can be seen throughout the built-in apps and operating system with its rounded corners, drop shadows, and transparency effects. As part of the new design, Windows 11 features a material called “Mica.” This creates a layering effect depending on what the desktop background is. For example, a light background will change the application windows to a lighter hue while darker backgrounds do the opposite. It also allows the desktop background to have subtle transparency through the windows. Mica is already noticeable in the current Preview build with the File Explorer.

In the video session, Gallo goes on to explain that Mica is fully optimized for rendering so the transparency and rounded corners should not affect performance. Mica doesn’t sample the desktop wallpaper every frame while instead opting to only blur the image once. By contrast, the Acrylic “material” creates a live background of whatever is beneath it which uses more resources.

Astute readers will remember that Windows Vista was notorious for bogging down slower machines with its Aero theme. At the time, Aero was a massive change from how Windows XP looked with its glass-like transparencies and reflections. The only way to gain performance was to downgrade to Aero Classic which did not look nearly as good.

According to Gallo, people running Windows 11 versions of apps will use Mica while computers on older versions of Windows will automatically default to those themes instead. This should improve performance across the board while simplifying software development. The goal is to get the “best version of the app everywhere you go.”