Just Download & Extract the Above Zip File provided, then edit the script.js file with a good text / code editor like Sublime Text ( Check Google ) & then save the changes & then view the index.html file on the internet browser. That's all.
This is a Browser Based, Cross Platform, Supporting all Operating Systems, Easy Application.
If needed, you can change the value of the Timer from 15 seconds to any other value, by Searching & Replacing all occurences of 15 in index.html & script.js files.
If necessary, Please change the charset="UTF-8" to charset="Your Charset" to match your language's charset value in the index.html file. Check Google if you need to know your language's html charset value.
This Application works offline, without needing an Internet Connection.
Also, run this application on your internet browsers in Kiosk mode, for maximum secrecy. For details, please refer : https://ostechnix.com/launch-web-browsers-in-kiosk-mode-full-screen-from-cli/ See Below.