When i was a little kid, I was really scared of the dark. But then I came to understand, dark just means the absence of photons in the visible wavelength -- 400 to 700 nanometers. Then i thought, well, its really silly to be afraid of a lack of photons. Then i wasn't afraid of the dark anymore after that.
Elon Musk

border-block-end-width

The border-block-end-width CSS property defines the width of the logical block-end border of an element, which maps to a physical border width depending on the element's writing mode, directionality, and text orientation. It corresponds to the border-top-width, border-right-width, border-bottom-width, or border-left-width property depending on the values defined for writing-mode, direction, and text-orientation.
border-block-end-width css reference