a "paste on" demonstration
That could be useful...
I remixed this project (see here) to follow the mouse. I also added some more variables such as magnification and easing.
Easing controls how fast the magnifier moves to the mouse.
Magnification controls how big the result would look.
Yes - lovely project. 
And lends itself well for further mods like tethrarxitet version
I took that one and added some key presses to control the magnification
White on black: I like it ! (it's subtle)
I just added a solid black shadow.
I like how background color still works as a pen color.