Update: More apps are getting the fluent design.
If you don't already know, Microsoft Fluent Design is a new design system coming to Windows 10, read more here.
Some of the apps that Microsoft have created now have the fluent design in their latest updates. Some of the apps that now have the Fluent Design are the Calculator app and the Groove Music app. Shown below is the Fluent Design in the Calculator app, the app now has a transparent background when not in tablet mode, it also has a circle effect when you click or tap on the buttons.
Below is the Fluent Design in the Groove Music app, a light effect is shown around the cursor.
Unfortunately, although the Fluent Design is available in the latest stable versions of these apps, it is still quite buggy and incomplete. Throughout the next few weeks, we will probably see this new design become available for more of Microsoft's apps.
If you want to see the Fluent Design in these apps for yourself, open them up and have a look, if you don't have automatic store app updates on or they didn't update automatically, go to the Store app, select your profile picture and choose 'Downloads and updates' from there, you can click the 'Check for updates' button to install new updates. Alternatively, you can update just the apps you want by finding them in the store and selecting the update button on the app's page.
What do you think of the new design in these apps, let us know in the comments!