/* DiagHub Design System */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&family=JetBrains+Mono:wght@500;600&display=swap');

:root {
    --dh-bg: #f6f8fa;
    --dh-bg-subtle: #eef2f6;
    --dh-surface: #ffffff;
    --dh-surface-raised: #ffffff;
    --dh-text: #0f172a;
    --dh-text-secondary: #334155;
    --dh-muted: #64748b;
    --dh-border: #e2e8f0;
    --dh-border-strong: #cbd5e1;

    --dh-teal-50: #f0fdfa;
    --dh-teal-100: #ccfbf1;
    --dh-teal-500: #14b8a6;
    --dh-teal-600: #0d9488;
    --dh-teal-700: #0f766e;

    --dh-blue-50: #eff6ff;
    --dh-blue-500: #3b82f6;
    --dh-blue-600: #2563eb;

    --dh-amber-50: #fffbeb;
    --dh-amber-500: #f59e0b;
    --dh-amber-600: #d97706;

    --dh-red-50: #fef2f2;
    --dh-red-500: #ef4444;
    --dh-red-600: #dc2626;

    --dh-accent: var(--dh-teal-600);
    --dh-accent-hover: var(--dh-teal-700);
    --dh-accent-muted: var(--dh-teal-50);

    --dh-radius-sm: 6px;
    --dh-radius: 10px;
    --dh-radius-lg: 14px;
    --dh-radius-xl: 20px;

    --dh-shadow-xs: 0 1px 2px rgba(15, 23, 42, 0.04);
    --dh-shadow-sm: 0 1px 3px rgba(15, 23, 42, 0.06), 0 1px 2px rgba(15, 23, 42, 0.04);
    --dh-shadow-md: 0 4px 12px rgba(15, 23, 42, 0.06), 0 2px 4px rgba(15, 23, 42, 0.04);
    --dh-shadow-lg: 0 12px 32px rgba(15, 23, 42, 0.08);

    --dh-font: 'Inter', system-ui, -apple-system, sans-serif;
    --dh-mono: 'JetBrains Mono', ui-monospace, monospace;

    --dh-space-xs: 0.25rem;
    --dh-space-sm: 0.5rem;
    --dh-space-md: 1rem;
    --dh-space-lg: 1.5rem;
    --dh-space-xl: 2rem;
    --dh-space-2xl: 3rem;
    --dh-space-3xl: 4rem;

    --dh-content-width: 68ch;
    --dh-page-width: 1200px;
    --dh-header-height: 64px;

    --dh-transition: 0.18s ease;
}

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

html {
    scroll-behavior: smooth;
    -webkit-font-smoothing: antialiased;
}

body {
    margin: 0;
    font-family: var(--dh-font);
    font-size: 1rem;
    line-height: 1.65;
    color: var(--dh-text-secondary);
    background: var(--dh-bg);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

h1, h2, h3, h4, h5, h6 {
    color: var(--dh-text);
    font-weight: 600;
    line-height: 1.3;
    letter-spacing: -0.02em;
    margin: 0 0 var(--dh-space-md);
}

h1 { font-size: clamp(1.75rem, 4vw, 2.25rem); }
h2 { font-size: 1.25rem; }
h3 { font-size: 1.0625rem; }

p { margin: 0 0 var(--dh-space-md); max-width: var(--dh-content-width); }

a {
    color: var(--dh-accent);
    text-decoration: none;
    transition: color var(--dh-transition);
}
a:hover { color: var(--dh-accent-hover); }

img, svg { display: block; max-width: 100%; }

/* Layout */
.dh-container {
    width: 100%;
    max-width: var(--dh-page-width);
    margin: 0 auto;
    padding: 0 var(--dh-space-lg);
}

.dh-grid {
    display: grid;
    gap: var(--dh-space-lg);
}

.dh-grid--brands { grid-template-columns: repeat(auto-fill, minmax(140px, 1fr)); }
.dh-grid--cards { grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); }
.dh-grid--2 { grid-template-columns: repeat(2, 1fr); }

@media (max-width: 768px) {
    .dh-grid--2 { grid-template-columns: 1fr; }
}

/* Header */
.dh-header {
    position: sticky;
    top: 0;
    z-index: 100;
    height: var(--dh-header-height);
    background: rgba(255, 255, 255, 0.85);
    backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--dh-border);
}

.dh-header__inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 100%;
    gap: var(--dh-space-lg);
}

.dh-logo {
    display: flex;
    align-items: center;
    gap: var(--dh-space-sm);
    font-weight: 700;
    font-size: 1.125rem;
    color: var(--dh-text);
    letter-spacing: -0.03em;
}
.dh-logo:hover { color: var(--dh-text); }
.dh-logo__mark {
    width: 32px;
    height: 32px;
    background: var(--dh-accent);
    border-radius: var(--dh-radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    color: #fff;
    font-size: 0.875rem;
}

.dh-nav-toggle {
    display: none;
    background: none;
    border: 1px solid var(--dh-border);
    border-radius: var(--dh-radius-sm);
    padding: 0.5rem 0.75rem;
    cursor: pointer;
    color: var(--dh-text);
}

.dh-header__nav {
    display: flex;
    align-items: center;
    gap: var(--dh-space-md);
}

@media (max-width: 768px) {
    .dh-nav-toggle { display: block; }
    .dh-header__nav {
        display: none;
        position: absolute;
        top: var(--dh-header-height);
        left: 0;
        right: 0;
        background: var(--dh-surface);
        border-bottom: 1px solid var(--dh-border);
        padding: var(--dh-space-lg);
        flex-direction: column;
        box-shadow: var(--dh-shadow-md);
    }
    .dh-header__nav.is-open { display: flex; }
}

/* Search */
.dh-search {
    position: relative;
    width: 100%;
    max-width: 320px;
}

.dh-search--hero { max-width: 520px; }

.dh-search__wrap {
    display: flex;
    align-items: center;
    background: var(--dh-surface);
    border: 1px solid var(--dh-border);
    border-radius: var(--dh-radius-lg);
    padding: 0 var(--dh-space-md);
    transition: border-color var(--dh-transition), box-shadow var(--dh-transition);
}
.dh-search__wrap:focus-within {
    border-color: var(--dh-teal-500);
    box-shadow: 0 0 0 3px rgba(20, 184, 166, 0.15);
}

.dh-search__icon { color: var(--dh-muted); flex-shrink: 0; }

.dh-search__input {
    flex: 1;
    border: none;
    background: transparent;
    padding: 0.75rem var(--dh-space-sm);
    font-family: inherit;
    font-size: 0.9375rem;
    color: var(--dh-text);
    outline: none;
    min-width: 0;
}
.dh-search--hero .dh-search__input { padding: 1rem var(--dh-space-sm); font-size: 1rem; }

.dh-search__btn {
    background: var(--dh-accent);
    color: #fff;
    border: none;
    border-radius: var(--dh-radius);
    padding: 0.5rem 1rem;
    font-family: inherit;
    font-size: 0.875rem;
    font-weight: 500;
    cursor: pointer;
    transition: background var(--dh-transition);
    white-space: nowrap;
}
.dh-search__btn:hover { background: var(--dh-accent-hover); }
.dh-search--hero .dh-search__btn { padding: 0.625rem 1.25rem; }

.dh-search__dropdown {
    display: none;
    position: absolute;
    top: calc(100% + 6px);
    left: 0;
    right: 0;
    background: var(--dh-surface);
    border: 1px solid var(--dh-border);
    border-radius: var(--dh-radius-lg);
    box-shadow: var(--dh-shadow-lg);
    max-height: 360px;
    overflow-y: auto;
    z-index: 200;
}
.dh-search__dropdown.is-visible { display: block; }

.dh-search__result {
    display: block;
    padding: 0.75rem var(--dh-space-md);
    border-bottom: 1px solid var(--dh-border);
    color: var(--dh-text);
    transition: background var(--dh-transition);
}
.dh-search__result:hover { background: var(--dh-bg-subtle); color: var(--dh-text); }
.dh-search__result:last-child { border-bottom: none; }
.dh-search__result-type {
    font-size: 0.6875rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--dh-muted);
}
.dh-search__result-title { font-weight: 500; font-size: 0.9375rem; }
.dh-search__result-meta { font-size: 0.8125rem; color: var(--dh-muted); }

/* Breadcrumbs */
.dh-breadcrumbs {
    padding: var(--dh-space-lg) 0 var(--dh-space-sm);
    font-size: 0.8125rem;
}
.dh-breadcrumbs__list {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: 0.35rem;
    list-style: none;
    margin: 0;
    padding: 0;
}
.dh-breadcrumbs__item { display: flex; align-items: center; gap: 0.35rem; color: var(--dh-muted); }
.dh-breadcrumbs__item:not(:last-child)::after {
    content: '/';
    color: var(--dh-border-strong);
    margin-left: 0.15rem;
}
.dh-breadcrumbs__link { color: var(--dh-muted); }
.dh-breadcrumbs__link:hover { color: var(--dh-accent); }
.dh-breadcrumbs__current { color: var(--dh-text); font-weight: 500; }

/* Home */
.dh-home-hero {
    padding: var(--dh-space-3xl) 0 var(--dh-space-2xl);
    border-bottom: 1px solid var(--dh-border);
    background: linear-gradient(180deg, var(--dh-surface) 0%, var(--dh-bg) 100%);
}

.dh-home-hero__label {
    display: inline-flex;
    align-items: center;
    gap: 0.35rem;
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--dh-accent);
    background: var(--dh-accent-muted);
    padding: 0.35rem 0.75rem;
    border-radius: 999px;
    margin-bottom: var(--dh-space-lg);
}

.dh-home-hero__title {
    max-width: 16ch;
    margin-bottom: var(--dh-space-md);
}

.dh-home-hero__desc {
    font-size: 1.0625rem;
    color: var(--dh-muted);
    max-width: 42ch;
    margin-bottom: var(--dh-space-xl);
}

.dh-home-hero__stats {
    display: flex;
    gap: var(--dh-space-xl);
    margin-top: var(--dh-space-xl);
    font-size: 0.875rem;
    color: var(--dh-muted);
}
.dh-home-hero__stat strong { color: var(--dh-text); font-weight: 600; }

.dh-section {
    padding: var(--dh-space-2xl) 0;
}
.dh-section__head {
    display: flex;
    align-items: baseline;
    justify-content: space-between;
    margin-bottom: var(--dh-space-lg);
    gap: var(--dh-space-md);
}
.dh-section__title { margin: 0; font-size: 1.125rem; }

/* Brand card */
.dh-brand-card {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: var(--dh-space-xl) var(--dh-space-md);
    background: var(--dh-surface);
    border: 1px solid var(--dh-border);
    border-radius: var(--dh-radius-lg);
    text-align: center;
    color: var(--dh-text);
    transition: border-color var(--dh-transition), box-shadow var(--dh-transition), transform var(--dh-transition);
    min-height: 100px;
}
.dh-brand-card:hover {
    border-color: var(--dh-teal-500);
    box-shadow: var(--dh-shadow-md);
    transform: translateY(-2px);
    color: var(--dh-text);
}
.dh-brand-card__name { font-weight: 600; font-size: 0.9375rem; }

/* Code card */
.dh-code-card {
    display: block;
    padding: var(--dh-space-lg);
    background: var(--dh-surface);
    border: 1px solid var(--dh-border);
    border-radius: var(--dh-radius-lg);
    color: var(--dh-text);
    transition: border-color var(--dh-transition), box-shadow var(--dh-transition), transform var(--dh-transition);
}
.dh-code-card:hover {
    border-color: var(--dh-teal-500);
    box-shadow: var(--dh-shadow-md);
    transform: translateY(-1px);
    color: var(--dh-text);
}
.dh-code-card__top {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: var(--dh-space-sm);
}
.dh-code-card__title {
    font-weight: 500;
    font-size: 0.9375rem;
    margin: 0 0 0.35rem;
    line-height: 1.4;
}
.dh-code-card__meta { font-size: 0.8125rem; color: var(--dh-muted); margin: 0; }

/* Appliance card */
.dh-appliance-card {
    display: flex;
    align-items: center;
    gap: var(--dh-space-md);
    padding: var(--dh-space-lg);
    background: var(--dh-surface);
    border: 1px solid var(--dh-border);
    border-radius: var(--dh-radius-lg);
    color: var(--dh-text);
    transition: border-color var(--dh-transition), box-shadow var(--dh-transition);
}
.dh-appliance-card:hover {
    border-color: var(--dh-teal-500);
    box-shadow: var(--dh-shadow-sm);
    color: var(--dh-text);
}
.dh-appliance-card__icon {
    width: 44px;
    height: 44px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--dh-bg-subtle);
    border-radius: var(--dh-radius);
    font-size: 1.25rem;
}
.dh-appliance-card__name { font-weight: 600; font-size: 0.9375rem; margin: 0 0 0.15rem; }
.dh-appliance-card__count { font-size: 0.8125rem; color: var(--dh-muted); margin: 0; }

/* Badges */
.dh-code-badge {
    font-family: var(--dh-mono);
    font-weight: 600;
    font-size: 0.875rem;
    padding: 0.3rem 0.65rem;
    background: var(--dh-accent-muted);
    color: var(--dh-accent);
    border: 1px solid var(--dh-teal-100);
    border-radius: var(--dh-radius-sm);
}
.dh-code-badge--lg { font-size: 1.125rem; padding: 0.45rem 0.85rem; }

.dh-severity {
    font-size: 0.6875rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    padding: 0.25rem 0.55rem;
    border-radius: 999px;
}
.dh-severity--critical { background: var(--dh-red-50); color: var(--dh-red-600); }
.dh-severity--warning { background: var(--dh-amber-50); color: var(--dh-amber-600); }
.dh-severity--info { background: var(--dh-blue-50); color: var(--dh-blue-600); }

/* Document layout */
.dh-doc {
    display: grid;
    grid-template-columns: 1fr 220px;
    gap: var(--dh-space-2xl);
    padding: var(--dh-space-lg) 0 var(--dh-space-3xl);
    align-items: start;
}

@media (max-width: 1024px) {
    .dh-doc { grid-template-columns: 1fr; }
    .dh-doc__toc { display: none; }
}

.dh-doc__main { min-width: 0; max-width: 720px; }

.dh-doc__header {
    margin-bottom: var(--dh-space-xl);
    padding-bottom: var(--dh-space-xl);
    border-bottom: 1px solid var(--dh-border);
}

.dh-doc__badges {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: var(--dh-space-sm);
    margin-bottom: var(--dh-space-md);
}

.dh-doc__copy-btn {
    display: inline-flex;
    align-items: center;
    gap: 0.35rem;
    background: var(--dh-bg-subtle);
    border: 1px solid var(--dh-border);
    border-radius: var(--dh-radius-sm);
    padding: 0.35rem 0.65rem;
    font-family: inherit;
    font-size: 0.75rem;
    font-weight: 500;
    color: var(--dh-muted);
    cursor: pointer;
    transition: all var(--dh-transition);
    margin-left: auto;
}
.dh-doc__copy-btn:hover { border-color: var(--dh-teal-500); color: var(--dh-accent); }
.dh-doc__copy-btn.is-copied { background: var(--dh-accent-muted); color: var(--dh-accent); border-color: var(--dh-teal-100); }

.dh-lede {
    font-size: 1.0625rem;
    line-height: 1.7;
    color: var(--dh-text-secondary);
    max-width: var(--dh-content-width);
    margin-bottom: 0;
}

/* TOC */
.dh-doc__toc {
    position: sticky;
    top: calc(var(--dh-header-height) + var(--dh-space-lg));
}

.dh-toc__title {
    font-size: 0.6875rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--dh-muted);
    margin-bottom: var(--dh-space-md);
}

.dh-toc__list {
    list-style: none;
    margin: 0;
    padding: 0;
    border-left: 2px solid var(--dh-border);
}

.dh-toc__link {
    display: block;
    padding: 0.4rem 0 0.4rem var(--dh-space-md);
    font-size: 0.8125rem;
    color: var(--dh-muted);
    border-left: 2px solid transparent;
    margin-left: -2px;
    transition: color var(--dh-transition), border-color var(--dh-transition);
}
.dh-toc__link:hover { color: var(--dh-text); }
.dh-toc__link.is-active {
    color: var(--dh-accent);
    border-left-color: var(--dh-accent);
    font-weight: 500;
}

/* Doc sections */
.dh-doc-section {
    margin-bottom: var(--dh-space-2xl);
    scroll-margin-top: calc(var(--dh-header-height) + var(--dh-space-lg));
}

.dh-doc-section__title {
    display: flex;
    align-items: center;
    gap: var(--dh-space-sm);
    font-size: 1.0625rem;
    margin-bottom: var(--dh-space-lg);
    padding-bottom: var(--dh-space-sm);
    border-bottom: 1px solid var(--dh-border);
}

.dh-doc-section__icon {
    width: 28px;
    height: 28px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--dh-accent-muted);
    border-radius: var(--dh-radius-sm);
    color: var(--dh-accent);
    flex-shrink: 0;
}

/* Cause probability */
.dh-causes-table {
    display: flex;
    flex-direction: column;
    gap: var(--dh-space-md);
}

.dh-cause-row {
    padding: var(--dh-space-md) var(--dh-space-lg);
    background: var(--dh-surface);
    border: 1px solid var(--dh-border);
    border-radius: var(--dh-radius);
}

.dh-cause-row__head {
    display: flex;
    justify-content: space-between;
    align-items: baseline;
    gap: var(--dh-space-md);
    margin-bottom: var(--dh-space-sm);
}

.dh-cause-row__name { font-weight: 500; font-size: 0.9375rem; color: var(--dh-text); }
.dh-cause-row__pct {
    font-family: var(--dh-mono);
    font-size: 0.8125rem;
    font-weight: 600;
    color: var(--dh-accent);
    flex-shrink: 0;
}

.dh-progress {
    height: 4px;
    background: var(--dh-bg-subtle);
    border-radius: 999px;
    overflow: hidden;
}
.dh-progress__bar {
    height: 100%;
    background: linear-gradient(90deg, var(--dh-teal-500), var(--dh-teal-600));
    border-radius: 999px;
    transition: width 0.6s ease;
}

/* Solution steps */
.dh-steps {
    list-style: none;
    margin: 0;
    padding: 0;
    counter-reset: step;
}

.dh-step {
    display: flex;
    gap: var(--dh-space-md);
    padding: var(--dh-space-lg);
    background: var(--dh-surface);
    border: 1px solid var(--dh-border);
    border-radius: var(--dh-radius);
    margin-bottom: var(--dh-space-sm);
    counter-increment: step;
}

.dh-step__num {
    width: 28px;
    height: 28px;
    flex-shrink: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--dh-accent-muted);
    color: var(--dh-accent);
    font-size: 0.8125rem;
    font-weight: 600;
    border-radius: 999px;
}
.dh-step__num::before {
    content: counter(step);
}

.dh-step__text {
    font-size: 0.9375rem;
    color: var(--dh-text-secondary);
    padding-top: 0.15rem;
}

/* Info panel / warning */
.dh-panel {
    display: flex;
    gap: var(--dh-space-md);
    padding: var(--dh-space-lg);
    border-radius: var(--dh-radius);
    border: 1px solid;
    margin: var(--dh-space-xl) 0;
}

.dh-panel--info {
    background: var(--dh-blue-50);
    border-color: #bfdbfe;
    color: var(--dh-text-secondary);
}
.dh-panel--warning {
    background: var(--dh-amber-50);
    border-color: #fde68a;
}
.dh-panel--critical {
    background: var(--dh-red-50);
    border-color: #fecaca;
}

.dh-panel__icon { flex-shrink: 0; font-size: 1.125rem; }
.dh-panel__title { font-weight: 600; font-size: 0.875rem; color: var(--dh-text); margin: 0 0 0.25rem; }
.dh-panel__text { font-size: 0.875rem; margin: 0; line-height: 1.6; }

/* FAQ accordion */
.dh-faq { border: 1px solid var(--dh-border); border-radius: var(--dh-radius-lg); overflow: hidden; }

.dh-faq__item { border-bottom: 1px solid var(--dh-border); }
.dh-faq__item:last-child { border-bottom: none; }

.dh-faq__question {
    width: 100%;
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: var(--dh-space-md);
    padding: var(--dh-space-md) var(--dh-space-lg);
    background: var(--dh-surface);
    border: none;
    font-family: inherit;
    font-size: 0.9375rem;
    font-weight: 500;
    color: var(--dh-text);
    text-align: left;
    cursor: pointer;
    transition: background var(--dh-transition);
}
.dh-faq__question:hover { background: var(--dh-bg-subtle); }

.dh-faq__chevron {
    flex-shrink: 0;
    transition: transform var(--dh-transition);
    color: var(--dh-muted);
}
.dh-faq__item.is-open .dh-faq__chevron { transform: rotate(180deg); }

.dh-faq__answer {
    display: none;
    padding: 0 var(--dh-space-lg) var(--dh-space-lg);
    font-size: 0.9375rem;
    color: var(--dh-muted);
    line-height: 1.65;
}
.dh-faq__item.is-open .dh-faq__answer { display: block; }

/* Related */
.dh-related { margin-top: var(--dh-space-3xl); padding-top: var(--dh-space-2xl); border-top: 1px solid var(--dh-border); }
.dh-related__title { font-size: 1rem; margin-bottom: var(--dh-space-lg); }

/* Link card (symptom, part) */
.dh-link-card {
    display: block;
    padding: var(--dh-space-md) var(--dh-space-lg);
    background: var(--dh-surface);
    border: 1px solid var(--dh-border);
    border-radius: var(--dh-radius);
    color: var(--dh-text);
    transition: border-color var(--dh-transition), box-shadow var(--dh-transition);
}
.dh-link-card:hover {
    border-color: var(--dh-teal-500);
    box-shadow: var(--dh-shadow-sm);
    color: var(--dh-text);
}
.dh-link-card__type {
    font-size: 0.6875rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--dh-muted);
}
.dh-link-card__title { font-weight: 500; font-size: 0.9375rem; margin: 0.25rem 0 0; }

/* Search page */
.dh-search-page { padding: var(--dh-space-2xl) 0 var(--dh-space-3xl); }
.dh-search-page__title { margin-bottom: var(--dh-space-xl); }

.dh-search-group { margin-bottom: var(--dh-space-2xl); }
.dh-search-group__title {
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--dh-muted);
    margin-bottom: var(--dh-space-md);
}

/* Footer */
.dh-footer {
    margin-top: auto;
    padding: var(--dh-space-2xl) 0;
    background: var(--dh-surface);
    border-top: 1px solid var(--dh-border);
}
.dh-footer__inner {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
    gap: var(--dh-space-lg);
}
.dh-footer__brand { font-weight: 600; color: var(--dh-text); margin-bottom: 0.35rem; }
.dh-footer__desc { font-size: 0.8125rem; color: var(--dh-muted); max-width: 36ch; margin: 0; }
.dh-footer__links { display: flex; gap: var(--dh-space-lg); font-size: 0.8125rem; }
.dh-footer__links a { color: var(--dh-muted); }
.dh-footer__links a:hover { color: var(--dh-accent); }

/* Back to top */
.dh-back-top {
    position: fixed;
    bottom: var(--dh-space-lg);
    right: var(--dh-space-lg);
    width: 44px;
    height: 44px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--dh-surface);
    border: 1px solid var(--dh-border);
    border-radius: var(--dh-radius);
    box-shadow: var(--dh-shadow-md);
    color: var(--dh-muted);
    cursor: pointer;
    opacity: 0;
    visibility: hidden;
    transform: translateY(8px);
    transition: all var(--dh-transition);
    z-index: 90;
}
.dh-back-top.is-visible {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}
.dh-back-top:hover { border-color: var(--dh-teal-500); color: var(--dh-accent); }

/* 404 */
.dh-empty {
    text-align: center;
    padding: var(--dh-space-3xl) 0;
}
.dh-empty__title { margin-bottom: var(--dh-space-md); }
.dh-empty__desc { color: var(--dh-muted); margin-bottom: var(--dh-space-xl); }

/* Utility */
.dh-sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0,0,0,0);
    border: 0;
}

@media (prefers-reduced-motion: reduce) {
    html { scroll-behavior: auto; }
    *, *::before, *::after {
        animation-duration: 0.01ms !important;
        transition-duration: 0.01ms !important;
    }
}