Magic Box has been built on the SVG Language. It is a simple language describing vector commands. To get a little feeling for the language here is a list of tutorials and resources helping you understand SVG commands.
The most powerful are the path data. They help you describe any vector shape imaginable. The W3C site has an overview of all the commands plus some examples:
Apart from these path commands you can include a number of other SVG shapes in your Magic box drawing. These are (at the moment):