Question: In Western Europe, we currently have a long spell of warm and dry weather. The perfect moment to combine sunbathing with working from home. However, outside in the sun, the legibility of my laptop screen is greatly reduced when compared to inside the house/office, even when I maximize the display's brightness. Are there any tricks I can use to increase the legibility (and ultimately my productivity)?  

I'll share one trick I often use, but I'm definitely interested in more suggestions.

Answer: 
In my experience many command line users have bright font on dark background terminal emulators (usually white on black, or matrix-movie green on black), while in bright environments (e.g. outside work), a dark font on a bright background is more legible (black on white).

Of cause this mainly addresses command line users, afaik, office applications are already dark on bright.
To increase the legibility of a computer screen, arrangement should be made to control the fall of run rays directly on the computer screen. This can be done by covering the top of the computer by some wooden surface or cloth , in such a way that the area of the wooden surface or the cloth is more than the area of the top surface of the computer.