Some days ago on the Guix-devel mailing list Florian Paul Schmidt mentioned Redshift. Redshift adjusts the colour temperature of your screen according to the time of day, reducing strain on your eyes at night.

Now I don’t want to sound all evangelistic, but if you regularly code at night: install it. You’ll wish someone had told you about this years ago. Had Dr Dobbs still been around then Redshift would get my vote for their all-time Programmer Productivity Award.