Hi,
there are no arguments or parameters in the onclick event itself,
see here the documentation of the if() action:
http://krpano.com/docu/actions/#if
in the example code above only the local attributes (align,x,y) of the <plugin> element were used (compared/changed),
there the current value of the "align" attribute of the current plugin element was compared with the value 'center',
and if that comparisons was true or false the "changeorigin" action was called to change the "align" and "edge" settings of the current plugin to other values,
and after the if() the tween() actions were called to change/animate the x,y settings of the plugin to 0.0,
best regards,
Klaus