Ghostwriter is a text editor for Markdown.  It provides a relaxing,
distraction-free writing environment, whether your masterpiece is
that next blog post, your school paper, or your NaNoWriMo novel.

Create your own custom themes, write in fullscreen mode, or use
focus mode to concentrate on just one or more lines.  A live HTML
preview allows you to view the final formatting as you type.

WWW: http://wereturtle.github.io/ghostwriter/