/*
	DGSIS design tokens
	Aligned with docs/01_BRAND_BOOK.md + docs/03_DESIGN_SYSTEM.md:
	sober technical palette, high contrast, restrained accent.
	HEX working set (docs mark final brand HEX as later refinement).
*/

:root {
	--font-sans:
		system-ui,
		-apple-system,
		BlinkMacSystemFont,
		"Segoe UI",
		sans-serif;

	--space-unit: 8px;
	--content-width: 1200px;
	--section-max: 900px;

	--color-focus-ring: var(--color-text);
	--color-overlay-hover: color-mix(in srgb, var(--color-text) 4%, transparent);
}

/* Dark — primary engineering surface (existing production baseline) */
html[data-theme="dark"],
html[data-theme="system"] {
	--color-background: #0b0d10;
	--color-background-accent: #121821;
	--color-surface: #11151b;
	--color-text: #f5f7fa;
	--color-muted: #9aa4b2;
	--color-border: #202733;
	--color-accent: #6f93b0;
	--color-accent-muted: #4d6d86;
	--color-error: #d9a0a0;
	color-scheme: dark;
}

/* Light — cool technical gray (not warm cream) */
html[data-theme="light"] {
	--color-background: #eef1f5;
	--color-background-accent: #e2e8f0;
	--color-surface: #f7f9fc;
	--color-text: #12161c;
	--color-muted: #5c6675;
	--color-border: #cfd6e0;
	--color-accent: #3d6f8f;
	--color-accent-muted: #2f556e;
	--color-error: #a84848;
	color-scheme: light;
}

@media (prefers-color-scheme: light) {
	html[data-theme="system"] {
		--color-background: #eef1f5;
		--color-background-accent: #e2e8f0;
		--color-surface: #f7f9fc;
		--color-text: #12161c;
		--color-muted: #5c6675;
		--color-border: #cfd6e0;
		--color-accent: #3d6f8f;
		--color-accent-muted: #2f556e;
		--color-error: #a84848;
		color-scheme: light;
	}
}

*,
*::before,
*::after {
	box-sizing: border-box;
}

html {
	font-family: var(--font-sans);
	background:
		radial-gradient(
			1100px 520px at 8% -8%,
			var(--color-background-accent),
			transparent 58%
		),
		var(--color-background);
	color: var(--color-text);
	scroll-behavior: smooth;
}

body {
	margin: 0;
	min-height: 100vh;
}

a {
	color: inherit;
}

.skip-link {
	position: absolute;
	left: calc(var(--space-unit) * 2);
	top: calc(var(--space-unit) * -12);
	z-index: 20;
	padding: calc(var(--space-unit) * 1.5) calc(var(--space-unit) * 2);
	background: var(--color-surface);
	border: 1px solid var(--color-border);
	text-decoration: none;
}

.skip-link:focus {
	top: calc(var(--space-unit) * 2);
}

.site-header {
	border-bottom: 1px solid var(--color-border);
	backdrop-filter: blur(8px);
	background: color-mix(in srgb, var(--color-background) 88%, transparent);
	position: sticky;
	top: 0;
	z-index: 10;
}

.site-navigation {
	max-width: var(--content-width);
	margin: 0 auto;
	padding:
		calc(var(--space-unit) * 3)
		calc(var(--space-unit) * 6);
	display: flex;
	align-items: center;
	justify-content: space-between;
	gap: calc(var(--space-unit) * 3);
}

.site-logo {
	display: inline-flex;
	align-items: center;
	gap: calc(var(--space-unit) * 1.5);
	color: var(--color-text);
	text-decoration: none;
	font-weight: 650;
	letter-spacing: 0.08em;
	text-transform: uppercase;
}

.site-logo__mark {
	width: 1.75rem;
	height: 1.75rem;
	flex-shrink: 0;
	display: block;
	color: var(--color-text);
}

.site-navigation__end {
	display: flex;
	flex-wrap: wrap;
	align-items: center;
	justify-content: flex-end;
	gap: calc(var(--space-unit) * 3);
}

.site-navigation__links {
	display: flex;
	flex-wrap: wrap;
	justify-content: flex-end;
	gap: calc(var(--space-unit) * 3);
}

.site-navigation__links a {
	color: var(--color-muted);
	text-decoration: none;
	font-size: 0.95rem;
	transition: color 160ms ease;
}

.site-navigation__links a:hover,
.site-navigation__links a:focus-visible,
.site-navigation__links a[aria-current="page"] {
	color: var(--color-text);
}

.site-prefs {
	display: flex;
	align-items: center;
	gap: calc(var(--space-unit) * 2);
	padding-left: calc(var(--space-unit) * 2);
	border-left: 1px solid var(--color-border);
}

.lang-switch,
.theme-switch {
	display: inline-flex;
	align-items: center;
	gap: 2px;
}

.lang-switch__btn,
.theme-switch__btn {
	display: inline-flex;
	align-items: center;
	justify-content: center;
	min-width: 2rem;
	min-height: 2rem;
	padding: 0.25rem 0.4rem;
	margin: 0;
	border: 1px solid transparent;
	background: transparent;
	color: var(--color-muted);
	font: inherit;
	font-size: 0.75rem;
	font-weight: 600;
	letter-spacing: 0.06em;
	line-height: 1;
	text-decoration: none;
	cursor: pointer;
	transition:
		color 160ms ease,
		border-color 160ms ease,
		background-color 160ms ease;
}

.theme-switch__btn {
	padding: 0.35rem;
}

.lang-switch__btn:hover,
.theme-switch__btn:hover,
.lang-switch__btn:focus-visible,
.theme-switch__btn:focus-visible {
	color: var(--color-text);
}

.lang-switch__btn.is-active,
.theme-switch__btn.is-active {
	color: var(--color-text);
	border-color: var(--color-border);
	background: var(--color-surface);
}

.site-footer {
	border-top: 1px solid var(--color-border);
}

.site-footer__inner {
	max-width: var(--content-width);
	margin: 0 auto;
	padding:
		calc(var(--space-unit) * 6)
		calc(var(--space-unit) * 6);
}

.site-footer__brand {
	display: inline-flex;
	align-items: center;
	gap: calc(var(--space-unit) * 1.25);
	margin: 0;
	color: var(--color-text);
	font-size: 0.875rem;
	font-weight: 650;
	letter-spacing: 0.12em;
	text-transform: uppercase;
}

.site-footer__mark {
	width: 1.25rem;
	height: 1.25rem;
	display: block;
	color: var(--color-text);
}

.site-footer p {
	margin: calc(var(--space-unit) * 1.5) 0 0;
	font-size: 0.875rem;
}

.site-footer__meta {
	display: flex;
	flex-wrap: wrap;
	gap: calc(var(--space-unit) * 1.5);
}

.site-footer__meta a {
	color: var(--color-muted);
	text-decoration: none;
	transition: color 160ms ease;
}

.site-footer__meta a:hover,
.site-footer__meta a:focus-visible {
	color: var(--color-text);
}

main {
	max-width: var(--content-width);
	margin: 0 auto;
	padding:
		calc(var(--space-unit) * 8)
		calc(var(--space-unit) * 6);
}

h1 {
	font-size: clamp(2.5rem, 5vw, 4rem);
	line-height: 1.1;
	letter-spacing: -0.03em;
	margin: calc(var(--space-unit) * 2) 0 0;
}

h2 {
	margin: 0;
}

p {
	color: var(--color-muted);
	font-size: 1.125rem;
}

.page-intro {
	max-width: 760px;
	padding-top: calc(var(--space-unit) * 4);
	animation: rise 700ms ease-out both;
}

.page-intro__eyebrow,
.hero__eyebrow {
	margin: 0;
	color: var(--color-accent);
	font-size: 0.875rem;
	letter-spacing: 0.08em;
	text-transform: uppercase;
}

.page-intro__description {
	max-width: 640px;
	margin-top: calc(var(--space-unit) * 3);
}

.hero {
	max-width: 760px;
	padding-top: calc(var(--space-unit) * 12);
	animation: rise 750ms ease-out both;
}

.hero__description {
	max-width: 600px;
	margin-top: calc(var(--space-unit) * 3);
}

.hero__actions {
	display: flex;
	flex-wrap: wrap;
	gap: calc(var(--space-unit) * 2);
	margin-top: calc(var(--space-unit) * 5);
}

.hero__action,
.contact__action {
	display: inline-block;
	color: var(--color-text);
	text-decoration: none;
	border: 1px solid var(--color-border);
	padding:
		calc(var(--space-unit) * 1.5)
		calc(var(--space-unit) * 3);
	transition:
		border-color 160ms ease,
		background-color 160ms ease,
		color 160ms ease;
}

.hero__action {
	margin-top: 0;
	border-color: var(--color-accent-muted);
	background: color-mix(in srgb, var(--color-accent) 12%, transparent);
}

.hero__action--secondary {
	color: var(--color-muted);
	border-color: var(--color-border);
	background: transparent;
}

.hero__action:hover,
.hero__action:focus-visible,
.contact__action:hover,
.contact__action:focus-visible {
	border-color: var(--color-accent);
	background: color-mix(in srgb, var(--color-accent) 18%, transparent);
	color: var(--color-text);
}

.approach,
.engineering,
.work,
.contact {
	margin-top: calc(var(--space-unit) * 16);
	max-width: var(--section-max);
	animation: rise 850ms ease-out both;
}

.approach h2,
.engineering h2,
.work h2,
.contact h2 {
	font-size: clamp(2rem, 4vw, 3rem);
	line-height: 1.2;
	letter-spacing: -0.02em;
}

.approach__description,
.engineering__description,
.work__description,
.contact__description {
	max-width: 700px;
	margin-top: calc(var(--space-unit) * 3);
}

.approach__items,
.engineering__items,
.work__items {
	display: grid;
	gap: calc(var(--space-unit) * 6);
	margin-top: calc(var(--space-unit) * 8);
}

.approach__item,
.engineering__item,
.work__item {
	border-top: 1px solid var(--color-border);
	padding-top: calc(var(--space-unit) * 3);
}

.approach__item h3,
.engineering__item h3,
.work__item h3 {
	margin: 0;
	font-size: 1.25rem;
}

.approach__item p,
.engineering__item p,
.work__item p {
	margin-top: calc(var(--space-unit) * 2);
}

.work__placeholder {
	margin-top: calc(var(--space-unit) * 6);
	padding-top: calc(var(--space-unit) * 3);
	border-top: 1px solid var(--color-border);
}

.provisional-note {
	margin-top: calc(var(--space-unit) * 3);
	color: var(--color-muted);
	font-size: 0.9375rem;
	letter-spacing: 0.02em;
}

.case {
	max-width: var(--section-max);
	margin-top: calc(var(--space-unit) * 12);
	padding-top: calc(var(--space-unit) * 4);
	border-top: 1px solid var(--color-border);
}

.case__eyebrow {
	margin: 0;
	color: var(--color-accent);
	font-size: 0.8125rem;
	letter-spacing: 0.08em;
	text-transform: uppercase;
}

.case h2 {
	margin-top: calc(var(--space-unit) * 2);
	font-size: clamp(1.6rem, 3vw, 2.2rem);
	line-height: 1.2;
	letter-spacing: -0.02em;
}

.case__summary {
	max-width: 700px;
	margin-top: calc(var(--space-unit) * 2);
}

.case__grid {
	display: grid;
	gap: calc(var(--space-unit) * 4);
	margin-top: calc(var(--space-unit) * 6);
}

.case__grid h3 {
	margin: 0;
	font-size: 1.05rem;
}

.case__grid p {
	margin-top: calc(var(--space-unit) * 1.5);
	font-size: 1.05rem;
}

.contact-form {
	max-width: 560px;
	margin-top: calc(var(--space-unit) * 6);
	display: grid;
	gap: calc(var(--space-unit) * 3);
}

.contact-form__field {
	display: grid;
	gap: calc(var(--space-unit) * 1);
}

.contact-form__field label {
	font-size: 0.9375rem;
	color: var(--color-text);
}

.contact-form__optional {
	color: var(--color-muted);
	font-weight: 400;
}

.contact-form input,
.contact-form textarea {
	width: 100%;
	margin: 0;
	padding: calc(var(--space-unit) * 1.5) calc(var(--space-unit) * 2);
	border: 1px solid var(--color-border);
	border-radius: 0;
	background: var(--color-surface);
	color: var(--color-text);
	font: inherit;
}

.contact-form textarea {
	resize: vertical;
	min-height: 9rem;
}

.contact-form input:focus-visible,
.contact-form textarea:focus-visible {
	outline: 2px solid var(--color-accent);
	outline-offset: 2px;
}

.contact-form__hp {
	position: absolute;
	left: -10000px;
	width: 1px;
	height: 1px;
	overflow: hidden;
}

.contact-form__submit {
	justify-self: start;
	cursor: pointer;
	background: color-mix(in srgb, var(--color-accent) 12%, transparent);
	border-color: var(--color-accent-muted);
	font: inherit;
}

.contact-form__feedback {
	min-height: 1.5rem;
}

.contact-form__ok,
.contact-form__err {
	margin: 0;
	font-size: 1rem;
}

.contact-form__ok {
	color: var(--color-text);
}

.contact-form__err {
	color: var(--color-error);
}

.contact__note a {
	color: var(--color-text);
}

.section__link {
	margin-top: calc(var(--space-unit) * 5);
	font-size: 1rem;
}

.section__link a {
	color: var(--color-text);
	text-decoration: none;
	border-bottom: 1px solid var(--color-accent-muted);
	transition: border-color 160ms ease;
}

.section__link a:hover,
.section__link a:focus-visible {
	border-color: var(--color-accent);
}

.contact {
	padding-bottom: calc(var(--space-unit) * 8);
}

.contact__action {
	margin-top: calc(var(--space-unit) * 5);
}

.contact__note {
	max-width: 560px;
	margin-top: calc(var(--space-unit) * 4);
	font-size: 1rem;
}

.contact--page {
	margin-top: calc(var(--space-unit) * 10);
}

@keyframes rise {
	from {
		opacity: 0;
		transform: translateY(10px);
	}

	to {
		opacity: 1;
		transform: translateY(0);
	}
}

@media (min-width: 900px) {
	.approach__items,
	.engineering__items,
	.work__items {
		grid-template-columns: repeat(3, minmax(0, 1fr));
		gap: calc(var(--space-unit) * 4);
	}

	.case__grid {
		grid-template-columns: repeat(2, minmax(0, 1fr));
	}
}

@media (max-width: 768px) {
	main,
	.site-navigation,
	.site-footer__inner {
		padding-left: calc(var(--space-unit) * 3);
		padding-right: calc(var(--space-unit) * 3);
	}

	.site-navigation {
		align-items: flex-start;
		flex-direction: column;
	}

	.site-navigation__end {
		width: 100%;
		justify-content: space-between;
		align-items: flex-start;
	}

	.site-navigation__links {
		justify-content: flex-start;
		gap: calc(var(--space-unit) * 2);
	}

	.site-prefs {
		padding-left: 0;
		border-left: 0;
	}

	.hero {
		padding-top: calc(var(--space-unit) * 8);
	}

	h1 {
		font-size: clamp(2.2rem, 10vw, 3rem);
	}

	.approach,
	.engineering,
	.work,
	.contact {
		margin-top: calc(var(--space-unit) * 10);
	}
}

:focus-visible {
	outline: 2px solid var(--color-text);
	outline-offset: 4px;
}

@media (prefers-reduced-motion: reduce) {
	html {
		scroll-behavior: auto;
	}

	*,
	*::before,
	*::after {
		scroll-behavior: auto !important;
		transition-duration: 0.01ms !important;
		animation-duration: 0.01ms !important;
	}
}