def on_button(self, button_id):
# get the clicked button.
try:
level = self.levels[button_id]
except KeyError:
return
# remove any other description box.
self.kill_desc()
# get a unique name to register to close the description box.
unique = Unique()
close_name = unique.generate(level.name)
self.active_desc = close_name
# should now create a co-menu with the description.
child = self.parent.add_child(DescriptionBox, text=level.description,
closename=close_name)
child.resume()
