Treffer: Build a Responsive and Modern UI with CSS for WinJS Apps.

The article discusses the building of a responsive and modern user interface (UI) with Cascading Style Sheet (CSS) for Windows Library for JavaScript (WinJS) applications. The author explains that two basic style sheets or themes in files namely, dark, named ui-dark.css, and light, named ui-light.css, can be found on all project templates for Windows Store applicaitons built with JavaScript. According to the author, one can overwrite the built-in styles in one's CSS files.