woocommerce/plugins/woocommerce-blocks/assets/js/blocks/cart/inner-blocks/proceed-to-checkout-block/style.scss

.wc-block-cart__submit {
	position: relative;
	margin: 0 0 $gap 0;
}

.wc-block-cart__submit-button {
	width: 100%;
	margin: 0;
	box-sizing: border-box;
}

.wc-block-cart {
	.wc-block-cart__submit-container {
		padding: 0;
	}
}

@include breakpoint(">782px") {
	.wc-block-cart .wc-block-cart__submit-container--sticky {
		display: none;
	}
}

@include breakpoint("<782px") {
	.wc-block-cart .wc-block-cart__submit-container--sticky {
		background: $white;
		bottom: 0;
		left: 0;
		padding: $gap;
		position: fixed;
		width: 100%;
		z-index: 9999;
		box-sizing: border-box;

		&::before {
			box-shadow: 0 -10px 20px 10px currentColor;
			color: color.adjust($gray-400, $alpha: -0.7);
			content: "";
			height: 100%;
			left: 0;
			position: absolute;
			right: 0;
			top: 0;
		}
	}
}