Before going in any direction, it starts as a rough sketch for me. Planning my idea and understanding the direction before I crack open an application. That being said, when going the code route it makes since when trying to work out the usability and functionality of the project. Because an actual prototype can show the expected behavior in the environment it's meant to viewed in. It may be a bunch a plain boxes void of any style but it works. However, when it comes to the traditional meaning of the word "design", code falls short. Even using pre-built components required some design app to "skin" it. When determining the look at feel of a project I go from sketches to Photoshop / Sketch before going to code. Mainly because outside of using CSS to style elements, more complex skins need to be established before being applied to the project.