Relax your eyes от Andreea Neamtiu

About web-extension:

3 functionalities accessible from popup:
-apply styles to your current tab for relaxing your eyes, using neutral colors
-timer on page for reminding you how much time do you have till sleep hour, counting down and hide the content of the page when time is off
-reminder for birthdays

Technical functionalities:

popup page & popup script
messaging content <> background <> popup
options
external .txt files in JSON format
DOM injection
jQuery
ajax requests

manifest.json keys:

permissions
browser_action
content_scripts
background
options_ui

APIs:

tabs.sendMessage()
runtime.onMessage
browser.tabs.onActivated
browser.tabs.onUpdated