Comment on page
Note that Gum uses XNA so the XNA runtime must be installed here:
Gum is a general-purpose UI tool for games, mockups, and websites. Gum saves to an XML format which you can include in your projects, but also supports a plugin system (using MEF) for custom exports.
Gum combines the power of programming concepts such as inheritance, instancing, and default/overriding variable values with a easy-to-use visual editor.