Staring at the phone screen can put a lot of strain on your eyes and cause eye fatigue.
Give your eyes a break by applying the 20-20-20 rule.
Every 20 minutes, take a 20-second break and focus your eyes on something at least 20 feet (7m) away.

Features:
• Notifies you after 20 minutes to give your eyes a break
• Starts countdown automatically when the screen is turned on
• Configure the notification behavior the way you like
• start and stop the service manually
• confirm brake in notification
• take care of your eyes 😉
• AD free

Android 8+ Users please read:
On Devices running Android 8 and higher you'll receive a notification telling you the 20 20 20 App is draining the battery in the background.
This is a default notification which is shown for every app using a background service even if it isn't using much power at all. The 20 20 20 service is only counting down 20 minutes as soon as its started. This doesn't require much power or cpu capacity. To verify this claim your self, you can check the Battery statistics after a day of running the 20 20 20 app.