I find all seven of these quite clever and useful.
I particularly like using custom properties when you can sneak a variation into a place where you’d normally have to re-declare a whole big chunk of code.
.some-element {
background-color: hsla(
var(--h, 120),
var(--s, 50),
var(--l, 50),
var(--a, 1)
);
}
.some-element.darker {
--l: 20;
}
Nice.