Screensavers were originally a way to prevent burn-in on older CRT monitors. The now-classic moving images in early operating systems were created to keep any single pixel on the screen from remaining in place for too long, leaving behind a ghost on the display. Modern screens like the OLED ones on Samsung's Galaxy S8 can also suffer from burn-in. Since the new flagship's Home button is virtual now, the company had to do something to prevent it from getting burned in to your display. The solution? Moving the Home button image around a little bit.