woocommerce/packages/woocommerce-blocks/assets/js/blocks/cart-checkout/checkout/styles/style.scss

.wp-block-woocommerce-checkout {
	margin: 0;

	.with-scroll-to-top__scroll-point {
		top: -96px;
	}
}

.wp-block-woocommerce-checkout.is-loading {
	display: flex;
	flex-wrap: wrap;
	margin: 0 auto $gap;
	position: relative;
	.wp-block-woocommerce-checkout-totals-block {
		width: 35%;
		padding-left: percentage(math.div($gap-large, 1060px));
	}
	.wp-block-woocommerce-checkout-fields-block {
		width: 65%;
		padding-right: percentage(math.div($gap-largest, 1060px)); // ~1060px is the default width of the content area in Storefront.
	}
	.wp-block-woocommerce-checkout-totals-block,
	.wp-block-woocommerce-checkout-fields-block {
		box-sizing: border-box;
		margin: 0;

		> div {
			@include placeholder();
			margin: 0 0 1.5em 0;
			display: none;
		}
		.wp-block-woocommerce-checkout-contact-information-block,
		.wp-block-woocommerce-checkout-payment-block {
			min-height: 10em;
			display: block;
		}
		.wp-block-woocommerce-checkout-shipping-address-block {
			min-height: 24em;
			display: block;
		}
		.wp-block-woocommerce-checkout-actions-block {
			width: 50%;
			min-height: 4em;
			margin-left: 50%;
			display: block;
		}
		.wp-block-woocommerce-checkout-order-summary-block {
			min-height: 47em;
			display: block;
		}
		.wc-block-components-panel > h2 {
			@include font-size(regular);
			@include reset-box();
			@include reset-typography();
			.wc-block-components-panel__button {
				font-weight: 400;
			}
		}
		.wc-block-components-totals-item,
		.wc-block-components-panel {
			padding-left: $gap;
			padding-right: $gap;
		}
	}
}
// Skeleton is shown before mobile classes are appended.
@media only screen and (max-width: 700px) {
	.wp-block-woocommerce-checkout.is-loading {
		flex-direction: column;
		margin: 0 auto $gap;

		.wp-block-woocommerce-checkout-fields-block {
			padding: 0;
			width: 100%;
		}
		.wp-block-woocommerce-checkout-totals-block {
			padding: 0;
			width: 100%;
			.wc-block-components-totals-item,
			.wc-block-components-panel {
				padding-left: 0;
				padding-right: 0;
			}
		}
	}
}

// For Twenty Twenty we need to increase specificity a bit more.
.theme-twentytwenty .wp-block-woocommerce-checkout.is-loading {
	.wp-block-woocommerce-checkout-totals-block .wc-block-components-panel > h2 {
		@include font-size(large);
		@include reset-box();
	}
}