Microsoft has announced that it has open sourced the Windows Calculator on GitHub under the MIT License. Microsoft is seeking more community contributions and ideas in the development of Windows Calculator. Reviewing the Windows Calculator code will allow developers to learn how to work with Microsoft technologies. Reviewing the Calculator code is a great way to learn about the latest Microsoft technologies like the Universal Windows Platform, XAML, and Azure Pipelines. Through this project, developers can learn from Microsoft's full development lifecycle, as well as reuse the code to build their own experiences. It's also a great example of Fluent app design. To make this even easier, we will be contributing custom controls and API extensions that we use in Calculator and other apps, to projects like the Windows Community Toolkit and the Windows UI Library.