Very nice, my eyes are saved

At the present it is the best. Great stuff!

It is enabled by default on any new website; it remembers each mode on a per-site basis (including the mode no 4 which equates to a "disabled" state). And has shortcuts, including an on/off one.

(Personally I would have preferred it disabled by default, and with on/off toggle button instead of the cycling-modes action the button has, which is made necessary by the presence of 4 modes. But one can't make everybody happy:))

Why not post a "lite" version with just 2 modes (on/off) triggered by one button and one short-key?

(Another suggestion: the button has an ugly icon. It should be changed to monochrome or gray.)