Great idea but I see nothing, just a blue field.
It looks like it's displaying the field to the proper dimensions but it's just blank.
Also, a little more clarity in the directions would be helpful. Especially in the path name. I tried several ways to address the file.mm but nothing. Example, I used the absolute path from root in Linux, I tried root assuming that it was the ./wordpress/path... tried move the file into the plugin directory. All nothing.