shinkan , it will always be black
take a look at this picture
that's the HTML structure of the index.html file , when you export ,
what does the plugin do , is it apply animation on the Body that contains the Div that contains the Canvas that you see , so behind the Body there is nothing:p , there is the HTML Markup , but it's not good to apply things on that markup
if there was a canvas for each layout , it will be more easy and i can make smthng better than this plugin :p :p , but it will be a laggy app cause of multiple canvas elements and rendering :p