woocommerce/plugins/woocommerce-blocks/packages/checkout/panel/style.scss

.wc-block-components-panel.has-border {
	@include with-translucent-border( 1px 0 );

	+ .wc-block-components-panel.has-border::after {
		border-top-width: 0;
	}
}

.wc-block-components-panel.has-border.no-top-border {
	@include with-translucent-border( 1px 0 );
	&::after {
		border-top-width: 0;
	}
}

.wc-block-components-panel__button {
	@include reset-box();
	height: auto;
	line-height: 1;
	margin-top: em(6px);
	padding-right: #{24px + $gap-smaller};
	padding-top: em($gap-small - 6px);
	position: relative;
	text-align: left;
	width: 100%;
	word-break: break-word;

	&[aria-expanded="true"] {
		padding-bottom: em($gap-small - 6px);
		margin-bottom: em(6px);
	}

	&,
	&:hover,
	&:focus,
	&:active {
		@include reset-typography();
		background: transparent;
		box-shadow: none;
	}

	> .wc-block-components-panel__button-icon {
		fill: currentColor;
		position: absolute;
		right: 0;
		top: 50%;
		transform: translateY(-50%);
		width: auto;
	}
}

.wc-block-components-panel__content {
	padding-bottom: em($gap);

	// Ensures the panel contents are not visible for any theme that tweaked the
	// `display` property of div elements.
	&[hidden] {
		display: none;
	}
}

// Extra classes for specificity.
.theme-twentytwentyone.theme-twentytwentyone.theme-twentytwentyone .wc-block-components-panel__button {
	background-color: inherit;
	color: inherit;
}

.theme-twentytwenty .wc-block-components-panel__button,
.theme-twentyseventeen .wc-block-components-panel__button {
	background: none transparent;
	color: inherit;

	&.wc-block-components-panel__button:hover,
	&.wc-block-components-panel__button:focus {
		background: none transparent;
	}
}