My eye doctor told me a trick to avoid eye fatigue from extended computer usage. Every 20 minutes, take a 20 second break. I'm still learning Swift 3 (and Cocoa), and decided to practice by making an app that forces you to take breaks.
Every 20 minutes, this app will take over your screen for 20 seconds, reminding you to rest your eyes.
20 seconds every
20 minutes for
20/20 vision
... That's 2020. 😎