Ever notice how people texting at night have that eerie blue glow? Or wake up ready to write down the Next Great Idea, and get blinded by your computer screen? During the day, computer screens look good—they're designed to look like the sun. But, at 9PM, 10PM, or 3AM, you probably shouldn't be looking at the sun. f.lux fixes this: it makes the color of your computer's display adapt to the time of day, warm at night and like sunlight during the day.