<?xml version="1.0"?>
<window title="Movable HUD Window"
        xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"
        width="300" height="200"
        style="background: transparent; -moz-appearance: none;">
    <titlebar flex="1" oncommand="close()"
            style="background: rgba(30, 30, 30, 0.9);
                   -moz-border-radius: 10px;
                   -moz-box-shadow: 0 1px 8px rgba(0, 0, 0, 0.8);
                   margin: 8px 12px 16px;">
  <p style="color:white;">
  A custom XUL window
  </p>
  </titlebar>
</window>