Heh, Hemingway is a cute idea, I had not seen that before.
It seems a bit miscalibrated though. I tried pasting in the current front-page article from The Guardian (http://www.theguardian.com/world/2015/apr/24/obama-drone-str...), and it becomes almost completely red ("27 out of 37 sentences are very hard to read"). If it categorizes ordinary newspaper prose as "very hard", I wonder what kind of audience it is aimed at.