/* ============================================================
   Zemtrion.org — Documentation Style CSS
   Mobile-first, semantic, readable
   ============================================================ */

/* ----- CSS Custom Properties ----- */
:root {
    --color-bg:          #f8f9fb;
    --color-surface:     #ffffff;
    --color-border:      #e2e6ea;
    --color-text:        #1a1d23;
    --color-text-muted:  #6b7280;
    --color-primary:     #1e40af;
    --color-primary-h:   #1d3a99;
    --color-accent:      #3b82f6;
    --color-accent-light:#eff6ff;
    --color-header-bg:   #0f172a;
    --color-header-text: #f1f5f9;
    --color-footer-bg:   #0f172a;
    --color-footer-text: #94a3b8;
    --color-tag-bg:      #e0f2fe;
    --color-tag-text:    #0369a1;

    --font-sans:   system-ui, -apple-system, 'Segoe UI', Roboto, Arial, sans-serif;
    --font-mono:   'Fira Code', 'Cascadia Code', Consolas, monospace;
    --font-size-base: 1rem;
    --line-height: 1.75;

    --radius-sm:  4px;
    --radius-md:  8px;
    --radius-lg:  12px;

    --shadow-sm:  0 1px 3px rgba(0,0,0,.08);
    --shadow-md:  0 4px 16px rgba(0,0,0,.10);

    --max-width: 1100px;
    --sidebar-w: 240px;
    --spacing-xs: .375rem;
    --spacing-sm: .75rem;
    --spacing-md: 1.25rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3.5rem;
}

/* ----- Reset ----- */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html { font-size: 16px; scroll-behavior: smooth; }

body {
    font-family: var(--font-sans);
    font-size: var(--font-size-base);
    line-height: var(--line-height);
    color: var(--color-text);
    background: var(--color-bg);
    -webkit-font-smoothing: antialiased;
}

a {
    color: var(--color-primary);
    text-decoration: none;
}
a:hover, a:focus { color: var(--color-primary-h); text-decoration: underline; }
a:focus-visible { outline: 2px solid var(--color-accent); outline-offset: 2px; border-radius: var(--radius-sm); }

img { max-width: 100%; height: auto; display: block; border-radius: var(--radius-md); }

ul, ol { padding-left: 1.5rem; }

/* ----- Header ----- */
.site-header {
    background: var(--color-header-bg);
    color: var(--color-header-text);
    position: sticky;
    top: 0;
    z-index: 100;
    box-shadow: 0 2px 8px rgba(0,0,0,.3);
}
.header-inner {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 var(--spacing-md);
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 56px;
}

.site-logo {
    display: flex;
    align-items: center;
    gap: .5rem;
    color: var(--color-header-text);
    text-decoration: none;
    font-weight: 700;
    font-size: 1.125rem;
    letter-spacing: -.02em;
}
.site-logo:hover { color: var(--color-accent); text-decoration: none; }
.logo-icon { color: var(--color-accent); font-size: 1rem; }
.logo-dot { color: var(--color-accent); }

/* Mobile nav toggle */
.nav-toggle {
    display: flex;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: var(--spacing-xs);
    border-radius: var(--radius-sm);
}
.nav-toggle span {
    display: block;
    width: 22px;
    height: 2px;
    background: var(--color-header-text);
    border-radius: 2px;
    transition: transform .2s, opacity .2s;
}
.nav-toggle[aria-expanded="true"] span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.nav-toggle[aria-expanded="true"] span:nth-child(2) { opacity: 0; }
.nav-toggle[aria-expanded="true"] span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

/* Nav — mobile first */
.site-nav {
    position: absolute;
    top: 56px;
    left: 0;
    right: 0;
    background: var(--color-header-bg);
    padding: var(--spacing-sm) 0;
    display: none;
    box-shadow: 0 4px 12px rgba(0,0,0,.3);
}
.site-nav.open { display: block; }

.nav-list { list-style: none; padding: 0; margin: 0; }
.nav-item { border-bottom: 1px solid rgba(255,255,255,.06); }
.nav-link {
    display: block;
    padding: .625rem var(--spacing-md);
    color: var(--color-header-text);
    font-size: .9375rem;
    opacity: .85;
    transition: background .15s, opacity .15s;
}
.nav-link:hover, .nav-link:focus { background: rgba(255,255,255,.07); opacity: 1; text-decoration: none; color: white; }
.nav-link.active { opacity: 1; color: var(--color-accent); border-left: 3px solid var(--color-accent); }

/* Desktop nav */
@media (min-width: 768px) {
    .nav-toggle { display: none; }
    .site-nav { position: static; display: block; background: none; padding: 0; box-shadow: none; }
    .nav-list { display: flex; gap: .25rem; }
    .nav-item { border: none; }
    .nav-link { padding: .375rem .625rem; border-radius: var(--radius-sm); font-size: .875rem; }
    .nav-link.active { border-left: none; border-bottom: 2px solid var(--color-accent); }
}

/* ----- Layout: page wrapper ----- */
.page-wrapper {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: var(--spacing-lg) var(--spacing-md);
}

/* ----- Hero Section (index) ----- */
.hero {
    background: var(--color-header-bg);
    color: white;
    padding: var(--spacing-xl) var(--spacing-md);
    text-align: center;
}
.hero-inner { max-width: 760px; margin: 0 auto; }
.hero h1 {
    font-size: clamp(1.75rem, 4vw, 2.75rem);
    font-weight: 700;
    line-height: 1.2;
    margin-bottom: var(--spacing-md);
}
.hero-lead {
    font-size: clamp(1rem, 2vw, 1.2rem);
    color: #94a3b8;
    max-width: 600px;
    margin: 0 auto var(--spacing-lg);
}
.hero-img {
    border-radius: var(--radius-lg);
    max-height: 380px;
    object-fit: cover;
    width: 100%;
    margin: 0 auto;
    box-shadow: var(--shadow-md);
}

/* ----- Topics Grid (index) ----- */
.section-title {
    font-size: 1.5rem;
    font-weight: 700;
    margin-bottom: var(--spacing-md);
    color: var(--color-text);
}
.section-title::after {
    content: '';
    display: block;
    width: 40px;
    height: 3px;
    background: var(--color-accent);
    margin-top: .35rem;
}

.topics-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: var(--spacing-md);
    margin: var(--spacing-lg) 0;
}
@media (min-width: 480px) { .topics-grid { grid-template-columns: repeat(2, 1fr); } }
@media (min-width: 900px) { .topics-grid { grid-template-columns: repeat(3, 1fr); } }

.topic-card {
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    padding: var(--spacing-md);
    transition: box-shadow .2s, border-color .2s;
    display: flex;
    flex-direction: column;
}
.topic-card:hover {
    box-shadow: var(--shadow-md);
    border-color: var(--color-accent);
    text-decoration: none;
}
.topic-icon {
    font-size: 2rem;
    margin-bottom: var(--spacing-sm);
    display: block;
}
.topic-card h2 {
    font-size: 1.0625rem;
    font-weight: 600;
    color: var(--color-primary);
    margin-bottom: .375rem;
}
.topic-card p {
    font-size: .9rem;
    color: var(--color-text-muted);
    line-height: 1.55;
    flex: 1;
}

/* ----- Doc Layout (inner pages) ----- */
.doc-layout {
    display: grid;
    grid-template-columns: 1fr;
    gap: var(--spacing-lg);
    max-width: var(--max-width);
    margin: 0 auto;
    padding: var(--spacing-lg) var(--spacing-md);
}
@media (min-width: 900px) {
    .doc-layout {
        grid-template-columns: var(--sidebar-w) 1fr;
        align-items: start;
    }
}

/* ----- Sidebar ----- */
.doc-sidebar {
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    padding: var(--spacing-md);
}
@media (min-width: 900px) {
    .doc-sidebar {
        position: sticky;
        top: 72px;
    }
}
.sidebar-title {
    font-size: .8125rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: .07em;
    color: var(--color-text-muted);
    margin-bottom: var(--spacing-sm);
}
.sidebar-nav { list-style: none; padding: 0; }
.sidebar-nav li { margin-bottom: .125rem; }
.sidebar-nav a {
    display: block;
    padding: .3125rem .5rem;
    border-radius: var(--radius-sm);
    font-size: .875rem;
    color: var(--color-text);
    transition: background .15s, color .15s;
}
.sidebar-nav a:hover, .sidebar-nav a:focus {
    background: var(--color-accent-light);
    color: var(--color-primary);
    text-decoration: none;
}
.sidebar-nav a.active-link {
    background: var(--color-accent-light);
    color: var(--color-primary);
    font-weight: 600;
}
.sidebar-separator { margin: var(--spacing-sm) 0; border: none; border-top: 1px solid var(--color-border); }

/* ----- Main Article ----- */
.doc-main {}
.article-header { margin-bottom: var(--spacing-lg); }
.article-header h1 {
    font-size: clamp(1.5rem, 3.5vw, 2.25rem);
    font-weight: 700;
    line-height: 1.25;
    margin-bottom: var(--spacing-sm);
}
.article-meta {
    font-size: .875rem;
    color: var(--color-text-muted);
    display: flex;
    flex-wrap: wrap;
    gap: .5rem var(--spacing-sm);
    align-items: center;
}
.tag {
    background: var(--color-tag-bg);
    color: var(--color-tag-text);
    padding: .125rem .5rem;
    border-radius: 99px;
    font-size: .8125rem;
    font-weight: 500;
}

.article-hero-img {
    width: 100%;
    max-height: 360px;
    object-fit: cover;
    border-radius: var(--radius-lg);
    margin-bottom: var(--spacing-lg);
}

/* ----- Article content ----- */
.article-content h2 {
    font-size: 1.375rem;
    font-weight: 700;
    margin: var(--spacing-lg) 0 var(--spacing-sm);
    color: var(--color-text);
    padding-bottom: .375rem;
    border-bottom: 2px solid var(--color-border);
}
.article-content h3 {
    font-size: 1.125rem;
    font-weight: 600;
    margin: var(--spacing-md) 0 .5rem;
    color: var(--color-text);
}
.article-content p {
    margin-bottom: var(--spacing-md);
    max-width: 68ch;
}
.article-content ul, .article-content ol {
    margin-bottom: var(--spacing-md);
    max-width: 68ch;
}
.article-content li { margin-bottom: .375rem; }

/* Info box */
.info-box {
    background: var(--color-accent-light);
    border-left: 4px solid var(--color-accent);
    border-radius: 0 var(--radius-md) var(--radius-md) 0;
    padding: var(--spacing-sm) var(--spacing-md);
    margin: var(--spacing-md) 0;
    font-size: .9375rem;
}
.info-box strong { color: var(--color-primary); }

/* Checklist */
.checklist { list-style: none; padding-left: 0; }
.checklist li { padding-left: 1.75rem; position: relative; margin-bottom: .5rem; }
.checklist li::before {
    content: '✓';
    position: absolute;
    left: 0;
    color: var(--color-accent);
    font-weight: 700;
}

/* Data table */
.data-table {
    width: 100%;
    border-collapse: collapse;
    margin: var(--spacing-md) 0;
    font-size: .9rem;
    overflow-x: auto;
    display: block;
}
.data-table th {
    background: #1e293b;
    color: white;
    text-align: left;
    padding: .625rem .875rem;
    font-weight: 600;
    font-size: .8125rem;
    text-transform: uppercase;
    letter-spacing: .04em;
}
.data-table td {
    padding: .5625rem .875rem;
    border-bottom: 1px solid var(--color-border);
    vertical-align: top;
}
.data-table tr:hover td { background: var(--color-accent-light); }

/* Table of contents */
.toc-box {
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    padding: var(--spacing-md);
    margin-bottom: var(--spacing-lg);
    max-width: 480px;
}
.toc-box summary {
    font-weight: 700;
    cursor: pointer;
    font-size: .9375rem;
    color: var(--color-text);
    list-style: none;
    display: flex;
    align-items: center;
    gap: .5rem;
}
.toc-box summary::-webkit-details-marker { display: none; }
.toc-box summary::before { content: '▸'; transition: transform .2s; }
details[open] .toc-box summary::before { transform: rotate(90deg); }
details[open] .toc-box { max-width: 100%; }
.toc-list { list-style: decimal; padding-left: 1.375rem; margin-top: var(--spacing-sm); }
.toc-list li { margin-bottom: .25rem; }
.toc-list a { font-size: .875rem; color: var(--color-primary); }

/* ----- Breadcrumb ----- */
.breadcrumb {
    margin-bottom: var(--spacing-md);
}
.breadcrumb-list {
    list-style: none;
    padding: 0;
    display: flex;
    flex-wrap: wrap;
    gap: .25rem;
    font-size: .8125rem;
    color: var(--color-text-muted);
}
.breadcrumb-item + .breadcrumb-item::before {
    content: '/';
    margin-right: .25rem;
    color: var(--color-border);
}
.breadcrumb-item a { color: var(--color-text-muted); }
.breadcrumb-item a:hover { color: var(--color-primary); }
.breadcrumb-item.active { color: var(--color-text); }

/* ----- Related ----- */
.related-section {
    margin-top: var(--spacing-xl);
    padding-top: var(--spacing-lg);
    border-top: 2px solid var(--color-border);
}
.related-title {
    font-size: 1.125rem;
    font-weight: 700;
    margin-bottom: var(--spacing-sm);
}
.related-list { list-style: none; padding: 0; display: flex; flex-direction: column; gap: .5rem; }
.related-item { font-size: .9375rem; }
.related-link { font-weight: 600; }
.related-desc { color: var(--color-text-muted); font-size: .875rem; }

/* ----- FAQ ----- */
.faq-list { list-style: none; padding: 0; }
.faq-item {
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    margin-bottom: .625rem;
    overflow: hidden;
}
.faq-item summary {
    padding: var(--spacing-sm) var(--spacing-md);
    font-weight: 600;
    cursor: pointer;
    list-style: none;
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: .9375rem;
    gap: .5rem;
    color: var(--color-text);
    user-select: none;
}
.faq-item summary::-webkit-details-marker { display: none; }
.faq-arrow {
    font-size: .75rem;
    color: var(--color-accent);
    transition: transform .2s;
    flex-shrink: 0;
}
.faq-item[open] .faq-arrow { transform: rotate(180deg); }
.faq-body {
    padding: 0 var(--spacing-md) var(--spacing-sm);
    font-size: .9375rem;
    color: var(--color-text);
    border-top: 1px solid var(--color-border);
    padding-top: var(--spacing-sm);
}
.faq-body p, .faq-body ul { margin-bottom: .5rem; }

/* ----- Index intro strip ----- */
.intro-strip {
    display: grid;
    grid-template-columns: 1fr;
    gap: var(--spacing-lg);
    margin: var(--spacing-lg) 0;
    align-items: start;
}
@media (min-width: 700px) {
    .intro-strip { grid-template-columns: 1fr 1fr; }
}
.intro-strip img { border-radius: var(--radius-lg); }
.intro-text h2 { font-size: 1.375rem; font-weight: 700; margin-bottom: var(--spacing-sm); }
.intro-text p { color: var(--color-text-muted); font-size: .9375rem; }

/* ----- Content card (used on index secondary) ----- */
.content-cards {
    display: grid;
    grid-template-columns: 1fr;
    gap: var(--spacing-md);
    margin: var(--spacing-lg) 0;
}
@media (min-width: 600px) { .content-cards { grid-template-columns: repeat(2, 1fr); } }

.content-card {
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    padding: var(--spacing-md);
}
.content-card h3 { font-size: 1rem; font-weight: 700; margin-bottom: .375rem; }
.content-card p { font-size: .875rem; color: var(--color-text-muted); margin-bottom: var(--spacing-sm); }
.content-card a { font-size: .875rem; font-weight: 600; }

/* ----- Footer ----- */
.site-footer {
    background: var(--color-footer-bg);
    color: var(--color-footer-text);
    margin-top: var(--spacing-xl);
}
.footer-inner {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: var(--spacing-xl) var(--spacing-md) var(--spacing-lg);
    display: grid;
    grid-template-columns: 1fr;
    gap: var(--spacing-lg);
}
@media (min-width: 600px) {
    .footer-inner { grid-template-columns: repeat(3, 1fr); }
}
.footer-brand { font-size: 1.125rem; font-weight: 700; color: white; margin-bottom: .375rem; }
.footer-tagline { font-size: .875rem; }
.footer-heading { font-size: .8125rem; font-weight: 700; text-transform: uppercase; letter-spacing: .06em; color: #64748b; margin-bottom: var(--spacing-sm); }
.footer-nav { list-style: none; padding: 0; }
.footer-nav li { margin-bottom: .375rem; }
.footer-nav a { color: var(--color-footer-text); font-size: .875rem; }
.footer-nav a:hover { color: white; text-decoration: none; }
.footer-about { font-size: .875rem; line-height: 1.65; }
.footer-bottom {
    border-top: 1px solid rgba(255,255,255,.08);
    padding: var(--spacing-sm) var(--spacing-md);
    text-align: center;
    font-size: .8125rem;
    color: #475569;
}

/* ----- Utility ----- */
.visually-hidden { position: absolute; width: 1px; height: 1px; clip: rect(0,0,0,0); overflow: hidden; }
.text-muted { color: var(--color-text-muted); }
.mt-lg { margin-top: var(--spacing-lg); }
.mb-md { margin-bottom: var(--spacing-md); }