f.lux is a software that warms up your monitor’s colour at night. Wam up, as in making it less bright and more candle-ly and less sun-y. There’s probably a lot of science behind it, and I don’t know what magic they use, but it makes me feel sleepier when working on the computer at night. It helps me sleep, and cut down on late-night distractions.
It also makes hotkeys to dim the screen, which is useful when I’m just using the computer for music, and I don’t feel like turning the monitor off just so the screen won’t glare at me.
Pretty light too. No slowdown on my 5 years old computer while it’s running.