style.scss

$button-spacing-x: $grid-unit-10 + math.div($grid-unit-05, 2); // 10px
$button-spacing-y: math.div($grid-unit-15, 2); // 6px

.wp-block-search__button {
	margin-left: $button-spacing-x;
	word-break: normal;

	&.has-icon {
		line-height: 0;
	}

	svg {
		min-width: $grid-unit-30;
		min-height: $grid-unit-30;
		width: 1.25em;
		height: 1.25em;
		fill: currentColor;
		vertical-align: text-bottom;
	}
}

// These rules are set to zero specificity to keep the default styles for search buttons.
// They are needed for backwards compatibility.
:where(.wp-block-search__button) {
	border: 1px solid $gray-400;
	padding: $button-spacing-y $button-spacing-x;
}

.wp-block-search__inside-wrapper {
	display: flex;
	flex: auto;
	flex-wrap: nowrap;
	max-width: 100%;
}

.wp-block-search__label {
	width: 100%;
}

.wp-block-search__input {
	padding: $grid-unit-10;
	flex-grow: 1;
	margin-left: 0;
	margin-right: 0;
	min-width: 3rem;
	border: 1px solid $gray-600;
	// !important used to forcibly prevent undesired application of
	// text-decoration styles on the input field.
	text-decoration: unset !important;

	// Hides a redundant extra search icon on Mobile Safari.
	appearance: initial;
}

.wp-block-search.wp-block-search__button-only {
	.wp-block-search__button {
		margin-left: 0;
		// Prevent unintended text wrapping.
		flex-shrink: 0;
		max-width: 100%;
	}

	// Ensure minimum input field width in small viewports.
	.wp-block-search__button[aria-expanded="true"] {
		max-width: calc(100% - 100px);
	}

	.wp-block-search__inside-wrapper {
		transition-property: width;
		min-width: 0 !important;
	}

	.wp-block-search__input {
		transition-duration: 300ms;
		flex-basis: 100%;
	}

	// !important here to override inline styles on button only deselected view.
	&.wp-block-search__searchfield-hidden {
		overflow: hidden;

		.wp-block-search__inside-wrapper {
			overflow: hidden;
		}

		.wp-block-search__input {
			width: 0 !important;
			min-width: 0 !important;
			padding-left: 0 !important;
			padding-right: 0 !important;
			border-left-width: 0 !important;
			border-right-width: 0 !important;
			flex-grow: 0;
			margin: 0;
			flex-basis: 0;
		}
	}
}

// We are lowering the specificity so that the input element can override the rule for the input element inside the search block.
:where(.wp-block-search__input) {
	font-family: inherit;
	font-weight: inherit;
	font-size: inherit;
	line-height: inherit;
	letter-spacing: inherit;
}

// We are lowering the specificity so that the button element can override the rule for the button inside the search block.
:where(.wp-block-search__button-inside .wp-block-search__inside-wrapper) {
	padding: $grid-unit-05;
	border: 1px solid $gray-600;
	box-sizing: border-box;

	.wp-block-search__input {
		border-radius: 0;
		border: none;
		padding: 0 $grid-unit-05;

		&:focus {
			outline: none;
		}
	}

	// For lower specificity.
	:where(.wp-block-search__button) {
		padding: $grid-unit-05 $grid-unit-10;
	}
}

.wp-block-search.aligncenter .wp-block-search__inside-wrapper {
	margin: auto;
}

.wp-block[data-align="right"] .wp-block-search.wp-block-search__button-only {
	.wp-block-search__inside-wrapper {
		float: right;
	}
}