TouchDevelop is a novel, touch-first IDE originally written as a Windows Phone 7 app using C# and XAML. TouchDevelop lets you create WP7, Win8 and Web-apps directly on your phone, tablet, or desktop. Trying to build the JavaScript version, both for Win8 and the Web, we were frustrated by the complete lack of compile-time checking. We thus got very excited to be one of the very early adopters of TypeScript, a typed superset of JavaScript that compiles to idiomatic JavaScript.