basic.css

.mod {
	padding: 8px mod(18px, 5px) 1px calc(mod(15px, 6px) + 50%);
	transform: rotate(mod(-140deg, -90deg));
	width: mod(mod(-18px, 5px), 5px);
}

.rem {
	padding: 8px rem(18px, 5px) 1px calc(rem(15px, 6px) + 50%);
	transform: rotate(rem(-140deg, -90deg));
}

.mod-rem {
	font-size: mod(-18px, 5px);
	width: rem(-18px, 5px);
	transform: rotateX(mod(140deg, -90deg)) rotateY(rem(140deg, -90deg));
	height: rem(mod(mod(-18px, 5px), 5px), 2px);
}

.round {
	top: round(2.5px, 1px);
	right: round(nearest, 2.5px, 1px);
	bottom: round(up, 2.5px, 1px);
	left: round(down, 2.5px, 1px);
	inset: round(to-zero, 2.5px, 1px);
}

.round-multiple {
	top: round(15px, 4px);
	right: round(nearest, 15px, 4px);
	bottom: round(up, 15px, 7px);
	left: round(down, 15px, 4px);
	inset: round(to-zero, 15px, 4px);
}

.round-complex {
	left: round(nearest, mod(-18px, 5px), 2px);
	top: round(nearest, mod(mod(-18px, 5px), 5px), 2px);
	/* lower case */
	right: round(up, rem(mod(mod(8px, 5px), 7px), 15px), 8px);
	/* upper case */
	right: ROUND(UP, REM(mod(MOD(8px, 5px), 7px), 15px), 8px);
}

.unit {
	top: round(up, 25px, 1cm);
	bottom: round(down, 25cm, 10px);
	left: mod(735ms, 0.1s);
}

.invalid {
	font-size: mod(18px, 5rem);
	width: rem(var(--foo), 5px);
	padding: mod(Fo0px, 5px);
	left: mod(1px, 0px);
	right: mod(1px, 200px);
	inset: round(something, 15px, 4px);
	margin-top: round(nearest, 15px, 4px, 50px);
	margin-bottom: round(nearest, 15px, 4%);
	font-size: mod;
	font-size: mod();
	font-size: mod(1px);
	font-size: rem;
	font-size: rem();
	font-size: rem(1px);
	font-size: round;
	font-size: round();
	font-size: round(1px);
	color: color-mod(calc(1 + 1), 1);
}