40 / Colour

Difference Inversion

The words turn themselves into the opposite of whatever passes behind them, so they stay readable over a photograph, over white and over black — and then vanish over one particular grey.

also called mix-blend-mode · invert on crossing · self-inverting overlay

One property, no JavaScript, and the overlay never has to know what is behind it. What it cannot survive is mid-grey, where inverting a value returns very nearly the value you started from. Plan for that band rather than discovering it on the one slide that has it.

How it is built

mix-blend-mode: difference;