Play N-back while you read any book

Reading is a excellent exercise to the brain, why not mixing with N-back task?

What is N-back? https://en.wikipedia.org/wiki/N-back
How to play N-back? http://brainworkshop.sourceforge.net/tutorial.html
New study of Hopkins University say that N-back training augment working memory 30%: http://releases.jhu.edu/2017/10/17/johns-hopkins-finds-training-exercise-that-boosts-brain-power/

Test Read N-back Online: http://competicionmental.appspot.com/router?page=rnback3&en=1

Video Demo

Proof of Work:

file: https://github.com/vernetit/readnback/blob/master/js/app/rnback3.js
file: https://github.com/vernetit/readnback/blob/master/rnback3.php

Changes

New mode in select position for a better reading
Cleaning code (not used features: decrease in 500+ lines of code)

Thanks!