/* =====================================================
   6NN6C · SEO/GEO Theme · main.css
   Palette: Option E — Midnight Indigo + Gold Amber
   Typography: DM Sans / DM Mono, 500 weight, -0.3px tracking
   ===================================================== */

:root {
    /* 主色 */
    --color-primary:      #1e1b4b;
    --color-primary-600:  #312e81;
    --color-primary-400:  #4338ca;

    /* 强调色（金琥珀） */
    --color-accent:       #ca8a04;
    --color-accent-500:   #eab308;
    --color-accent-100:   #fef3c7;

    /* 文本 */
    --color-ink:          #0f172a;
    --color-ink-muted:    #475569;
    --color-ink-soft:     #64748b;

    /* 背景 */
    --color-bg:           #ffffff;
    --color-bg-soft:      #f8fafc;
    --color-bg-panel:     #f1f5f9;
    --color-bg-dark:      #0f172a;

    /* 边框 */
    --color-border:       #e2e8f0;
    --color-border-strong:#cbd5e1;

    /* 语义 */
    --color-success:      #059669;
    --color-warning:      #d97706;
    --color-danger:       #dc2626;

    /* 字体 */
    --font-sans: "DM Sans", -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
    --font-mono: "DM Mono", ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;

    /* 尺度 */
    --fs-xs:  0.8125rem;
    --fs-sm:  0.9375rem;
    --fs-base:1rem;
    --fs-lg:  1.125rem;
    --fs-xl:  1.375rem;
    --fs-2xl: 1.75rem;
    --fs-3xl: 2.25rem;
    --fs-4xl: 3rem;

    --lh-tight: 1.25;
    --lh-base:  1.65;
    --lh-loose: 1.8;

    /* 间距 */
    --space-1:  4px;
    --space-2:  8px;
    --space-3:  12px;
    --space-4:  16px;
    --space-5:  20px;
    --space-6:  24px;
    --space-8:  32px;
    --space-10: 40px;
    --space-12: 48px;
    --space-16: 64px;
    --space-20: 80px;
    --space-24: 96px;

    /* 圆角 / 阴影 */
    --radius-sm:   6px;
    --radius-md:   10px;
    --radius-lg:   16px;
    --radius-xl:   24px;
    --shadow-sm:   0 1px 2px rgba(15,23,42,.04);
    --shadow-md:   0 4px 16px rgba(15,23,42,.06);
    --shadow-lg:   0 12px 40px rgba(30,27,75,.12);

    /* 版面 */
    --container:    1160px;
    --container-sm: 760px;
    --letter-spacing: -0.3px;

    --header-h:   64px;
}

/* ===== Reset ===== */
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }
body {
    margin: 0;
    font-family: var(--font-sans);
    font-weight: 500;
    font-size: var(--fs-base);
    line-height: var(--lh-base);
    color: var(--color-ink);
    background: var(--color-bg);
    letter-spacing: var(--letter-spacing);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}
img, svg, video { max-width: 100%; height: auto; display: block; }
a { color: var(--color-primary-600); text-decoration: none; transition: color .16s ease; }
a:hover { color: var(--color-accent); text-decoration: underline; text-underline-offset: 3px; }
button { font: inherit; letter-spacing: inherit; cursor: pointer; }
input, textarea, select { font: inherit; letter-spacing: inherit; }
code, pre, kbd, samp { font-family: var(--font-mono); font-weight: 400; }

h1,h2,h3,h4,h5,h6 {
    font-weight: 700;
    line-height: var(--lh-tight);
    margin: 0 0 var(--space-4);
    color: var(--color-ink);
    letter-spacing: -0.5px;
}
h1 { font-size: var(--fs-4xl); }
h2 { font-size: var(--fs-3xl); }
h3 { font-size: var(--fs-2xl); }
h4 { font-size: var(--fs-xl); }
p { margin: 0 0 var(--space-4); }

/* ===== A11y ===== */
.screen-reader-text {
    position: absolute !important;
    width: 1px; height: 1px;
    padding: 0; margin: -1px; overflow: hidden;
    clip: rect(0,0,0,0);
    border: 0;
}
.skip-link:focus {
    position: absolute; left: 8px; top: 8px;
    padding: 8px 16px; background: var(--color-primary); color: #fff;
    z-index: 999; border-radius: var(--radius-sm);
    clip: auto; width: auto; height: auto;
}
:focus-visible {
    outline: 2px solid var(--color-accent);
    outline-offset: 2px;
    border-radius: 3px;
}

/* ===== Layout ===== */
.container {
    max-width: var(--container);
    margin: 0 auto;
    padding: 0 var(--space-5);
}
.container--content { max-width: var(--container-sm); }

/* ===== Header ===== */
.site-header {
    position: sticky;
    top: 0;
    z-index: 50;
    background: rgba(255,255,255,.92);
    backdrop-filter: saturate(180%) blur(14px);
    -webkit-backdrop-filter: saturate(180%) blur(14px);
    border-bottom: 1px solid var(--color-border);
}
.site-header__inner {
    max-width: var(--container);
    margin: 0 auto;
    padding: 0 var(--space-5);
    min-height: var(--header-h);
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: var(--space-6);
}
.site-brand { display: flex; flex-direction: column; gap: 2px; text-decoration: none; color: var(--color-ink); }
.site-brand:hover { text-decoration: none; color: var(--color-primary); }
.site-brand__mark {
    font-family: var(--font-mono);
    font-weight: 500;
    font-size: 1.125rem;
    letter-spacing: -0.3px;
    color: var(--color-ink);
}
.site-brand__accent {
    font-style: normal;
    color: var(--color-accent);
}
.site-brand__tag {
    font-size: var(--fs-xs);
    color: var(--color-ink-soft);
}

.menu-toggle {
    background: none; border: 0; padding: 8px;
    display: none; flex-direction: column; gap: 4px;
}
.menu-toggle__bar { width: 22px; height: 2px; background: var(--color-ink); border-radius: 2px; display: block; }

.site-nav .menu {
    list-style: none; padding: 0; margin: 0;
    display: flex; align-items: center; gap: var(--space-6);
    font-size: var(--fs-sm);
}
.site-nav .menu li { position: relative; }
.site-nav .menu a {
    display: inline-block;
    padding: 8px 0;
    color: var(--color-ink);
    text-decoration: none;
    border-bottom: 2px solid transparent;
}
.site-nav .menu a:hover,
.site-nav .menu .current-menu-item > a {
    color: var(--color-primary);
    border-bottom-color: var(--color-accent);
}
.site-nav .sub-menu {
    position: absolute;
    top: 100%; left: 0;
    min-width: 180px;
    list-style: none; padding: 8px 0; margin: 0;
    background: #fff;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-lg);
    display: none;
}
.site-nav .menu li:hover > .sub-menu,
.site-nav .menu li:focus-within > .sub-menu { display: block; }
.site-nav .sub-menu a { padding: 6px 16px; display: block; border-bottom: 0; }
.site-nav .sub-menu a:hover { background: var(--color-bg-soft); }

@media (max-width: 860px) {
    .menu-toggle { display: inline-flex; }
    .site-nav { display: none; position: absolute; top: var(--header-h); left: 0; right: 0; background: #fff; border-bottom: 1px solid var(--color-border); padding: var(--space-4); }
    .site-nav.is-open { display: block; }
    .site-nav .menu { flex-direction: column; align-items: flex-start; gap: var(--space-3); }
    .site-nav .sub-menu { position: static; box-shadow: none; border: 0; padding-left: var(--space-4); display: block; }
}

/* ===== Buttons ===== */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 10px 20px;
    font-weight: 600;
    font-size: var(--fs-sm);
    border-radius: var(--radius-md);
    border: 1px solid transparent;
    transition: background .16s ease, color .16s ease, border-color .16s ease, transform .06s ease;
    text-decoration: none;
    cursor: pointer;
}
.btn:hover { text-decoration: none; transform: translateY(-1px); }
.btn:active { transform: translateY(0); }
.btn--primary { background: var(--color-primary); color: #fff; }
.btn--primary:hover { background: var(--color-primary-600); color: #fff; }
.btn--ghost { background: transparent; color: var(--color-primary); border-color: var(--color-border-strong); }
.btn--ghost:hover { background: var(--color-bg-soft); color: var(--color-primary); }
.btn--accent { background: var(--color-accent); color: #fff; }
.btn--accent:hover { background: var(--color-accent-500); color: #fff; }

/* ===== Tags ===== */
.tag {
    display: inline-block;
    padding: 3px 10px;
    font-size: var(--fs-xs);
    border-radius: 999px;
    background: var(--color-bg-panel);
    color: var(--color-ink-muted);
    border: 1px solid var(--color-border);
    text-decoration: none;
    margin-right: 6px;
    margin-bottom: 6px;
}
.tag:hover { background: var(--color-primary); color: #fff; border-color: var(--color-primary); text-decoration: none; }
.tag--stage { background: var(--color-accent-100); color: #78350f; border-color: transparent; }
.tag--stage:hover { background: var(--color-accent); color: #fff; }
.tag--engine { background: rgba(67,56,202,.08); color: var(--color-primary-600); border-color: transparent; }

.tag-row { list-style: none; padding: 0; margin: var(--space-6) 0 0; display: flex; flex-wrap: wrap; gap: 0; }
.tag-row li { margin: 0; }

/* ===== Cards ===== */
.card {
    background: #fff;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    transition: border-color .16s ease, box-shadow .16s ease, transform .08s ease;
    overflow: hidden;
}
.card:hover { border-color: var(--color-primary-400); box-shadow: var(--shadow-md); transform: translateY(-2px); }
.card__link {
    display: block;
    padding: var(--space-6);
    color: inherit;
    text-decoration: none;
}
.card__link:hover { text-decoration: none; color: inherit; }
.card__eyebrow {
    font-family: var(--font-mono);
    font-size: var(--fs-xs);
    color: var(--color-accent);
    margin: 0 0 var(--space-2);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}
.card__title {
    font-size: var(--fs-xl);
    margin: 0 0 var(--space-3);
    color: var(--color-ink);
}
.card__excerpt {
    font-size: var(--fs-sm);
    color: var(--color-ink-muted);
    margin: 0 0 var(--space-3);
    line-height: var(--lh-base);
}
.card__meta {
    font-size: var(--fs-xs);
    color: var(--color-ink-soft);
    margin: 0;
}
.card__date {
    display: block;
    font-family: var(--font-mono);
    font-size: var(--fs-xs);
    color: var(--color-ink-soft);
    margin-bottom: var(--space-2);
}
.card__metric {
    font-family: var(--font-mono);
    font-size: 1.375rem;
    font-weight: 500;
    color: var(--color-primary);
    margin: 0 0 var(--space-3);
    letter-spacing: -0.3px;
}
.card__facts {
    display: flex;
    gap: var(--space-6);
    margin: 0;
    font-size: var(--fs-xs);
}
.card__facts div { margin: 0; }
.card__facts dt { color: var(--color-ink-soft); margin: 0 0 2px; }
.card__facts dd { margin: 0; color: var(--color-ink); font-family: var(--font-mono); }

.card-grid {
    list-style: none;
    padding: 0;
    margin: var(--space-8) 0 0;
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: var(--space-6);
}

/* ===== Breadcrumb ===== */
.breadcrumb {
    font-size: var(--fs-xs);
    color: var(--color-ink-soft);
    margin: var(--space-6) 0;
}
.breadcrumb ol {
    list-style: none; padding: 0; margin: 0;
    display: flex; flex-wrap: wrap; gap: 6px;
}
.breadcrumb li + li::before {
    content: "/";
    margin-right: 6px;
    color: var(--color-border-strong);
}
.breadcrumb a { color: var(--color-ink-muted); }
.breadcrumb [aria-current="page"] { color: var(--color-ink); }

/* ===== Page head ===== */
.page-head {
    margin: var(--space-8) 0 var(--space-10);
    padding-bottom: var(--space-6);
    border-bottom: 1px solid var(--color-border);
}
.page-head__title { margin: 0; }
.page-head__desc { margin: var(--space-3) 0 0; color: var(--color-ink-muted); }

/* ===== 404 ===== */
.error-404 { padding: var(--space-16) 0 var(--space-20); }
.error-404 .page-head { text-align: left; }
.error-404 .page-head__title {
    font-family: var(--font-mono);
    font-size: clamp(3.5rem, 10vw, 6rem);
    color: var(--color-primary);
    letter-spacing: -0.02em;
}
.error-404 .search-form { margin: var(--space-8) 0 var(--space-10); max-width: 540px; }
.error-404__links { margin-top: var(--space-10); }
.error-404__links h2 {
    font-family: var(--font-mono);
    font-size: var(--fs-sm);
    color: var(--color-accent);
    text-transform: uppercase;
    letter-spacing: 1px;
    margin: 0 0 var(--space-4);
}
.error-404__links ul {
    list-style: none;
    padding: 0;
    margin: 0;
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-3) var(--space-6);
}
.error-404__links a {
    color: var(--color-primary);
    text-decoration: none;
    border-bottom: 1px solid var(--color-border);
    padding-bottom: 2px;
    transition: color .16s ease, border-color .16s ease;
}
.error-404__links a:hover { color: var(--color-accent); border-bottom-color: var(--color-accent); }

/* ===== Archive ===== */
.archive-wrap { padding: var(--space-10) 0 var(--space-16); }
.archive-head { margin-bottom: var(--space-8); }
.archive-head h1 { margin: 0 0 var(--space-2); }
.archive-head p { color: var(--color-ink-muted); margin: 0; }

.pagination {
    margin: var(--space-10) 0;
    display: flex; justify-content: center; gap: var(--space-2);
}
.pagination .page-numbers {
    padding: 8px 14px;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-sm);
    color: var(--color-ink);
    text-decoration: none;
    font-size: var(--fs-sm);
}
.pagination .page-numbers.current { background: var(--color-primary); color: #fff; border-color: var(--color-primary); }
.pagination a.page-numbers:hover { border-color: var(--color-accent); color: var(--color-accent); text-decoration: none; }

/* ===== Footer ===== */
.site-footer {
    margin-top: var(--space-24);
    background: var(--color-primary);
    color: #e2e8f0;
}
.site-footer__inner {
    max-width: var(--container);
    margin: 0 auto;
    padding: var(--space-16) var(--space-5) var(--space-10);
    display: grid;
    grid-template-columns: 1.2fr 1fr 1fr 1fr;
    gap: var(--space-8);
}
.site-footer__col h3 {
    font-size: var(--fs-xs);
    color: rgba(255,255,255,.65);
    margin: 0 0 var(--space-4);
    text-transform: uppercase;
    letter-spacing: 1px;
    font-weight: 600;
}
.site-footer__col ul { list-style: none; padding: 0; margin: 0; }
.site-footer__col li { margin-bottom: var(--space-2); font-size: var(--fs-sm); }
.site-footer__col a { color: #e2e8f0; text-decoration: none; }
.site-footer__col a:hover { color: var(--color-accent-500); }
.site-footer__brand { font-family: var(--font-mono); font-size: 1.25rem; color: #fff; margin: 0 0 var(--space-3); }
.site-footer__desc { font-size: var(--fs-sm); color: rgba(255,255,255,.7); margin: 0; }
.site-footer__base {
    border-top: 1px solid rgba(255,255,255,.1);
    padding: var(--space-4) var(--space-5);
    max-width: var(--container);
    margin: 0 auto;
    font-size: var(--fs-xs);
    color: rgba(255,255,255,.55);
    text-align: center;
}

@media (max-width: 860px) {
    .site-footer__inner { grid-template-columns: 1fr 1fr; gap: var(--space-6); padding: var(--space-12) var(--space-5) var(--space-8); }
}
@media (max-width: 480px) {
    .site-footer__inner { grid-template-columns: 1fr; }
}

/* ===== Prose ===== */
/* .prose 用于首页段落；.post-body 用于单篇文章/页面的正文；.page-head__desc 用于聚合页面的简短引导段。 */
.prose,
.post-body,
.page-head__desc {
    font-size: var(--fs-lg);
    line-height: var(--lh-loose);
    color: var(--color-ink);
}
.prose,
.post-body { max-width: 68ch; }

.prose p, .post-body p, .page-head__desc p { margin: 0 0 var(--space-5); }
.prose h2, .post-body h2 { margin-top: var(--space-10); font-size: var(--fs-2xl); }
.prose h3, .post-body h3 { margin-top: var(--space-8); font-size: var(--fs-xl); }
.prose h4, .post-body h4 { margin-top: var(--space-6); font-size: var(--fs-lg); }
.prose ul, .prose ol,
.post-body ul, .post-body ol { margin: 0 0 var(--space-5); padding-left: 1.5em; }
.prose li, .post-body li { margin-bottom: var(--space-2); }
.prose a, .post-body a, .page-head__desc a {
    color: var(--color-primary-600);
    text-decoration: underline;
    text-underline-offset: 3px;
    text-decoration-color: rgba(67,56,202,.4);
}
.prose a:hover, .post-body a:hover, .page-head__desc a:hover {
    color: var(--color-accent);
    text-decoration-color: var(--color-accent);
}
.prose blockquote, .post-body blockquote {
    margin: var(--space-6) 0;
    padding: var(--space-4) var(--space-6);
    border-left: 3px solid var(--color-accent);
    background: var(--color-bg-soft);
    color: var(--color-ink-muted);
    font-style: normal;
    border-radius: 0 var(--radius-md) var(--radius-md) 0;
}
.prose blockquote p:last-child, .post-body blockquote p:last-child { margin-bottom: 0; }
.prose code, .post-body code {
    background: var(--color-bg-panel);
    padding: 2px 6px;
    border-radius: 4px;
    font-size: 0.875em;
    color: var(--color-primary);
    font-family: var(--font-mono);
}
.prose pre, .post-body pre {
    background: #0f172a;
    color: #e2e8f0;
    padding: var(--space-5);
    border-radius: var(--radius-md);
    overflow-x: auto;
    font-size: var(--fs-sm);
    line-height: 1.6;
    position: relative;
    margin: var(--space-6) 0;
    font-family: var(--font-mono);
}
.prose pre code, .post-body pre code { background: none; padding: 0; color: inherit; }
.prose img, .prose figure,
.post-body img, .post-body figure { margin: var(--space-6) 0; border-radius: var(--radius-md); }
.prose table, .post-body table {
    width: 100%;
    border-collapse: collapse;
    margin: var(--space-6) 0;
    font-size: var(--fs-sm);
}
.prose th, .prose td,
.post-body th, .post-body td {
    padding: 10px 14px;
    text-align: left;
    border-bottom: 1px solid var(--color-border);
    vertical-align: top;
}
.prose th, .post-body th { background: var(--color-bg-soft); font-weight: 600; }
.prose hr, .post-body hr { border: 0; height: 1px; background: var(--color-border); margin: var(--space-8) 0; }
.prose strong, .post-body strong { font-weight: 600; color: var(--color-primary); }