AppleScript 20-20-20 rule very simple application to protect your eye's vision. Every 20 minutes the app is ringing (then you should look at distant object), and after 20 seconds it rings again (then you can go back to work).

protectEyes.scpt

(* Installation instructions:
1. Download this file and open with Script Editor
2. Extract screenLockChecker.sh from this file and save in desired location
3. Edit PATH_TO_SCREEN_LOCK_CHECKER_SCRIPT to absolute path to the screenLockChecker.sh script
4. Go to File -> Export... -> set "File Format" to "Application" and click "Save"
5. (Optionally add to startup) Open system Preferences -> Search "Open at Login" -> add newly created app
*)
-- Author: howkymike 2022

repeat while true
	delay 60 * 20
	set scriptRes to do shell script "<PATH_TO_SCREEN_LOCK_CHECKER_SCRIPT>"
	if scriptRes is equal to "Screen unlocked" then
		say "ding dong ding dong ding dong" using "Bells"
		delay 20
		say "return return" using "Bells"
	end if
end repeat


(*  screenLockChecker.sh, credits: https://stackoverflow.com/a/66723000/5764479
#!/bin/sh

function screenIsLocked { [ "$(/usr/libexec/PlistBuddy -c "print :IOConsoleUsers:0:CGSSessionScreenIsLocked" /dev/stdin 2>/dev/null <<< "$(ioreg -n Root -d1 -a)")" = "true" ] && return 0 || return 1; }
function screenIsUnlocked { [ "$(/usr/libexec/PlistBuddy -c "print :IOConsoleUsers:0:CGSSessionScreenIsLocked" /dev/stdin 2>/dev/null <<< "$(ioreg -n Root -d1 -a)")" != "true" ] && return 0 || return 1; }

if screenIsLocked; then
    echo "Screen locked"
fi

if screenIsUnlocked; then
    echo "Screen unlocked"
fi
*)