It would be noce it it worked more like the "Blank your monitor + easy reading" addon for firefox.. (Dosent work from Firefox v57...

This app should have a key shortcut and user should be able to change that..
Be able to set a color schemas for background and foreground.. Might also be easier to add to the this add on then the current method since it dosent work properly on Mozillas add ons page...
Also when opening a new tab i have to click once again.. it would be better if it was either on or off..