BetterSelect/src/BetterSelect.css

better-select {
	--faded: color-mix(in oklab, currentcolor, transparent 60%);
	--highlight: color-mix(in oklab, currentcolor, transparent 90%);
	--overshoot: cubic-bezier(.2, 0, .2, 1.4);

	--h-padding: .8em;

	min-width: 14em;

	outline: none;

	&:focus {
		border-color: currentcolor;
	}

	[slot="placeholder"] {
		color: var(--faded);
	}

	&::part(display) {
		padding: .4rem var(--h-padding);

		gap: .4em;

		background: linear-gradient(to top, var(--highlight), transparent);
	}

	&, &::part(drop-down) {
		border: 1px solid var(--faded);
		border-radius: 3px;
	}

	&::part(drop-down) {
		transition-behavior: allow-discrete;
		transition-duration: .2s;
		transition-property: transform, display, opacity;
		transition-timing-function: var(--overshoot);
		margin-top: .2em;
		padding: .4rem 0;

		min-width: 100%;
	}

	&::part(search) {
		margin-block: .4em;
		line-height: 1.4em;
		margin-inline: var(--h-padding);
		display: none;
	}

	&.search::part(search) {
		display: block;
	}

	&::part(item) {
		line-height: 2em;
		transition: background-color .3s;
		padding-inline: var(--h-padding);
	}

	&::part(item):is(:hover, :focus) {
		background-color: var(--highlight);
	}

	&:not(:state(--open))::part(drop-down) {
		transform: scale(100%, 70%) translate(0, -30%);
		opacity: 0;
	}

	&::part(display)::after {
		margin-left: auto;
		display: inline-block;
		content: '\25be';
		color: var(--faded);
		line-height: 1em;
		transition: transform .3s var(--overshoot);
	}

	&:state(--open)::part(display)::after {
		transform: rotate(180deg);
	}
}