/* =========================================================
   135GEO Landing Page · Stylesheet
   颜色/字体/排版设计令牌（CSS Variables）
   ========================================================= */
/* 色系对齐 135 贴牌 GEO 页（dev5.135read.com/geo.html）：深灰底 + 橙红主色 */
:root {
    --bg-dark: #111111;
    --bg-darker: #050505;
    --bg-chat: #2a2a2a;
    --bg-user-msg: #2d2e3d;

    --card-bg: rgba(45, 46, 61, 0.55);
    --border-light: rgba(255, 255, 255, 0.08);

    --text-main: #ffffff;
    --text-muted: #afb3b6;
    --text-dim: #777777;
    --text-chat: #d1d1d1;

    /* 主色：橙红（与贴牌页 #fd5622 / #ff7010 / #ff7a00 系一致） */
    --accent-blue: #fd5622;
    --accent-purple: #ff7c2c;
    --accent-red: #ef4444;

    --gradient-primary: linear-gradient(135deg, #ff5e00 0%, #fd5622 42%, #ff7a00 100%);

    /* 左侧浮窗导航占位（与 .floating-nav 宽度协调） */
    --floating-nav-width: 188px;
    --floating-nav-offset: 28px;
    --site-header-height: 60px;
}

/* =========================================================
   Reset & Base
   ========================================================= */
* { box-sizing: border-box; margin: 0; padding: 0; }

html {
    scroll-behavior: smooth;
    scroll-padding-top: calc(var(--site-header-height) + 12px);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
                 "Hiragino Sans GB", "Microsoft YaHei", Roboto, "Helvetica Neue",
                 Arial, sans-serif;
    background-image: url(https://bcn.135editor.com/files/202604/images/geobeijing.gif);
    background-size: 100% 100%;
    color: var(--text-main);
    line-height: 1.6;
    overflow-x: hidden;
}

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

/* Screen-reader only (caption / a11y) */
.visually-hidden {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

/* =========================================================
   Layout
   ========================================================= */
.container { max-width: 1200px; margin: 0 auto; padding: 0 20px; }

section { padding: 100px 0; position: relative; }

.text-center { text-align: center; }

.grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 30px; }
.grid-2 { display: grid; grid-template-columns: repeat(2, 1fr); gap: 40px; }

/* =========================================================
   Typography
   ========================================================= */
.gradient-text {
    background: var(--gradient-primary);
    -webkit-background-clip: text;
            background-clip: text;
    -webkit-text-fill-color: transparent;
    font-weight: bold;
}

h2.section-title {
    font-size: 36px;
    margin-bottom: 16px;
    letter-spacing: 1px;
}

p.section-subtitle {
    color: var(--text-muted);
    font-size: 18px;
    margin-bottom: 60px;
}

/* =========================================================
   Buttons
   ========================================================= */
.btn {
    display: inline-block;
    background: var(--gradient-primary);
    color: #fff;
    padding: 14px 36px;
    border-radius: 8px;
    text-decoration: none;
    font-weight: 600;
    transition: transform 0.3s, box-shadow 0.3s, background 0.3s;
    border: none;
    cursor: pointer;
    font-family: inherit;
}
.btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 10px 28px rgba(253, 86, 34, 0.42);
}

.btn-outline {
    background: transparent;
    border: 1px solid var(--accent-blue);
    color: var(--accent-blue);
}
.btn-outline:hover { background: rgba(253, 86, 34, 0.12); }

.btn-sm { padding: 8px 24px; font-size: 14px; }
.btn-lg { font-size: 18px; padding: 16px 48px; }

/* =========================================================
   顶部导航（Logo + 立即体验）
   ========================================================= */
.site-header {
    position: sticky;
    top: 0;
    z-index: 210;
    min-height: var(--site-header-height);
    box-sizing: border-box;
    padding: 16px 0;
    border-bottom: 1px solid var(--border-light);
    background: rgba(17, 17, 17, 0.92);
    -webkit-backdrop-filter: blur(12px);
            backdrop-filter: blur(12px);
}
.nav-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
}
.logo {
    display: inline-flex;
    align-items: center;
    text-decoration: none;
    line-height: 0;
}
.logo__img {
    display: block;
    height: 28px;
    width: auto;
    max-width: 148px;
    object-fit: contain;
}
@media (max-width: 768px) {
    .logo__img {
        height: 24px;
        max-width: 128px;
    }
}

/* =========================================================
   左侧浮窗导航（仅章节锚点；桌面 fixed / 小屏底部条）
   ========================================================= */
.floating-nav {
    position: fixed;
    left: var(--floating-nav-offset);
    top: calc(var(--site-header-height) + 24px);
    bottom: 28px;
    transform: none;
    z-index: 200;
    width: var(--floating-nav-width);
    padding: 16px 14px;
    display: flex;
    flex-direction: column;
    align-items: stretch;
    justify-content: center;
    gap: 0;
    background: transparent;
    border: none;
    border-radius: 16px;
    box-shadow: none;
    max-height: calc(100vh - var(--site-header-height) - 52px);
    overflow-y: auto;
    -webkit-overflow-scrolling: touch;
}

.floating-nav__links {
    display: flex;
    flex-direction: column;
    gap: 2px;
}
.floating-nav__link {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 10px 12px;
    border-radius: 10px;
    font-size: 14px;
    color: var(--text-muted);
    text-decoration: none;
    transition: background 0.2s, color 0.2s;
}
.floating-nav__link:hover {
    color: var(--text-main);
    background: rgba(253, 86, 34, 0.14);
}
.floating-nav__link:focus-visible {
    outline: 2px solid var(--accent-blue);
    outline-offset: 2px;
}
.floating-nav__icon {
    flex-shrink: 0;
    width: 18px;
    height: 18px;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--accent-blue);
    opacity: 0.9;
}
.floating-nav__icon svg {
    width: 100%;
    height: 100%;
}
.floating-nav__link:hover .floating-nav__icon {
    opacity: 1;
}
.floating-nav__text {
    flex: 1;
    min-width: 0;
}

@media (max-width: 1023px) {
    html { scroll-padding-top: calc(var(--site-header-height) + 8px); }

    body {
        padding-bottom: 100px;
    }

    .floating-nav {
        left: 12px;
        right: 12px;
        top: auto;
        bottom: 12px;
        transform: none;
        width: auto;
        max-width: none;
        flex-direction: column;
        justify-content: flex-start;
        padding: 12px 12px;
        max-height: min(42vh, 320px);
        overflow-y: auto;
    }

    .floating-nav__links {
        flex-direction: row;
        flex-wrap: wrap;
        justify-content: center;
        gap: 6px;
    }
    .floating-nav__link {
        padding: 8px 12px;
        font-size: 13px;
    }
}

@media (max-width: 480px) {
    .floating-nav__link {
        padding: 7px 10px;
        font-size: 12px;
    }
    .floating-nav__icon {
        width: 16px;
        height: 16px;
    }
}

/* =========================================================
   Hero
   ========================================================= */
.hero {
    padding: 120px 0 80px;
    background: radial-gradient(circle at 50% -20%, rgba(253, 86, 34, 0.15), transparent 60%);
}
.hero h1 { font-size: 56px; line-height: 1.2; margin-bottom: 24px; font-weight: 800; }
.hero .hero-desc { font-size: 20px; color: var(--text-muted); max-width: 760px; margin: 0 auto 40px; }
.hero-btns { display: flex; gap: 20px; justify-content: center; flex-wrap: wrap; }

.hero-tag {
    color: var(--accent-blue);
    font-weight: 600;
    margin-bottom: 16px;
    display: inline-block;
    letter-spacing: 2px;
    padding: 6px 16px;
    border: 1px solid rgba(253, 86, 34, 0.3);
    border-radius: 100px;
    background: rgba(253, 86, 34, 0.05);
    font-size: 13px;
}

/* =========================================================
   Cards
   ========================================================= */
.card {
    background: var(--card-bg);
    border: 1px solid var(--border-light);
    border-radius: 16px;
    padding: 40px 30px;
    transition: all 0.3s ease;
}
.card:hover { border-color: var(--accent-blue); transform: translateY(-5px); }
.card h3 { font-size: 22px; margin-bottom: 16px; color: #fff; }
.card p { color: var(--text-muted); }
.card-icon { margin-bottom: 15px; }

.card-accent { border-color: rgba(253, 86, 34, 0.3); }

.step-num {
    font-size: 48px;
    font-weight: 900;
    color: rgba(255, 255, 255, 0.05);
    line-height: 1;
    margin-bottom: -20px;
    text-align: left;
}

/* =========================================================
   Section Backgrounds & Sizing
   ========================================================= */
.section-alt { background: rgba(255, 255, 255, 0.01); }
.section-comparison { background: radial-gradient(circle at 50% 50%, rgba(255, 124, 44, 0.08), transparent 70%); }
.section-compact { padding: 70px 0; }

/* =========================================================
   Definition Block & Comparison Table (What is GEO)
   ========================================================= */
.definition-card {
    background: var(--card-bg);
    border: 1px solid var(--border-light);
    border-radius: 16px;
    padding: 40px;
    margin-bottom: 40px;
    border-left: 4px solid var(--accent-blue);
}
.definition-card .term {
    color: var(--accent-blue);
    font-weight: 700;
    font-size: 18px;
    letter-spacing: 1px;
    margin-bottom: 12px;
    display: block;
}
.definition-card p {
    font-size: 17px;
    color: var(--text-chat);
    line-height: 1.8;
}

.comparison-table-wrapper {
    overflow-x: auto;
    border-radius: 16px;
    border: 1px solid var(--border-light);
    background: var(--card-bg);
}
.comparison-table {
    width: 100%;
    border-collapse: collapse;
    min-width: 640px;
}
.comparison-table th,
.comparison-table td {
    padding: 18px 24px;
    text-align: left;
    border-bottom: 1px solid var(--border-light);
    font-size: 15px;
}
.comparison-table thead th {
    background: rgba(253, 86, 34, 0.08);
    color: var(--text-main);
    font-weight: 700;
    font-size: 16px;
    letter-spacing: 0.5px;
}
.comparison-table thead th.col-geo {
    color: var(--accent-blue);
    background: rgba(253, 86, 34, 0.15);
}
.comparison-table tbody tr:last-child td { border-bottom: none; }
.comparison-table tbody tr:hover { background: rgba(255, 255, 255, 0.02); }
.comparison-table td:first-child {
    color: var(--text-muted);
    font-weight: 600;
    width: 15%;
    white-space: nowrap;
}
.comparison-table td.col-geo {
    color: var(--text-main);
    font-weight: 500;
    background: rgba(253, 86, 34, 0.04);
}

/* =========================================================
   Market Stats Band
   ========================================================= */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 24px;
    margin-bottom: 60px;
}
.stat-card {
    background: var(--card-bg);
    border: 1px solid var(--border-light);
    border-radius: 14px;
    padding: 28px 20px;
    text-align: center;
    transition: all 0.3s;
}
.stat-card:hover {
    border-color: var(--accent-blue);
    transform: translateY(-4px);
}
.stat-num {
    font-size: 36px;
    font-weight: 800;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
            background-clip: text;
    -webkit-text-fill-color: transparent;
    line-height: 1.1;
    margin-bottom: 8px;
}
.stat-num.stat-down {
    background: linear-gradient(135deg, #f59e0b 0%, #ef4444 100%);
    -webkit-background-clip: text;
            background-clip: text;
    -webkit-text-fill-color: transparent;
}
.stat-label { color: var(--text-main); font-size: 14px; font-weight: 600; margin-bottom: 4px; }
.stat-sub { color: var(--text-muted); font-size: 12px; }

/* =========================================================
   AI Processing Flow
   ========================================================= */
.ai-flow {
    display: flex;
    justify-content: space-between;
    align-items: stretch;
    gap: 12px;
    list-style: none;
}
.flow-node {
    flex: 1;
    background: var(--card-bg);
    border: 1px solid var(--border-light);
    border-radius: 14px;
    padding: 24px 16px;
    text-align: center;
    position: relative;
    transition: all 0.3s;
}
.flow-node:hover {
    border-color: var(--accent-blue);
    transform: translateY(-3px);
}
.flow-node .flow-index {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 36px;
    height: 36px;
    border-radius: 50%;
    background: var(--gradient-primary);
    color: #fff;
    font-weight: 700;
    font-size: 14px;
    margin-bottom: 14px;
}
.flow-node h4 { font-size: 16px; color: var(--text-main); margin-bottom: 6px; font-weight: 600; }
.flow-node p { color: var(--text-muted); font-size: 13px; line-height: 1.6; }
.flow-arrow {
    display: flex;
    align-items: center;
    color: var(--accent-blue);
    font-size: 22px;
    font-weight: 700;
    opacity: 0.7;
}

/* =========================================================
   4-Step Methodology Timeline
   ========================================================= */
.methodology-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 24px;
}
.methodology-card {
    background: var(--card-bg);
    border: 1px solid var(--border-light);
    border-radius: 16px;
    padding: 32px 24px;
    position: relative;
    transition: all 0.3s;
}
.methodology-card:hover {
    border-color: var(--accent-blue);
    transform: translateY(-5px);
}
.methodology-card .phase {
    font-size: 13px;
    font-weight: 700;
    color: var(--accent-blue);
    letter-spacing: 2px;
    margin-bottom: 8px;
}
.methodology-card h3 { font-size: 20px; margin-bottom: 14px; color: #fff; }
.methodology-card ul {
    list-style: none;
    color: var(--text-muted);
    font-size: 14px;
    line-height: 1.9;
}
.methodology-card ul li {
    padding-left: 18px;
    position: relative;
}
.methodology-card ul li::before {
    content: '';
    position: absolute;
    left: 0;
    top: 12px;
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background: var(--accent-blue);
}
.duration-tag {
    display: inline-block;
    font-size: 12px;
    padding: 3px 10px;
    border-radius: 20px;
    background: rgba(255, 124, 44, 0.15);
    color: var(--accent-purple);
    border: 1px solid rgba(255, 124, 44, 0.3);
    margin-bottom: 12px;
}

/* Subsection titles inside long sections */
.subsection-title {
    font-size: 24px;
    font-weight: 700;
    color: var(--text-main);
    margin: 56px 0 28px;
    text-align: center;
    letter-spacing: 0.5px;
}
/* :first-of-type 会把「区块内第一个 h3」的 margin-top 清零；「关键环节」前有 ai-flow 时也需要顶距。
   仅在与 section-subtitle 相邻时收紧顶距（导语已有 margin-bottom）。 */
p.section-subtitle + .subsection-title {
    margin-top: 0;
}
.subsection-lead {
    text-align: center;
    color: var(--text-muted);
    font-size: 16px;
    margin: -12px 0 36px;
    max-width: 720px;
    margin-left: auto;
    margin-right: auto;
}

/* Commercial value (why GEO matters) */
.benefit-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 20px;
    margin-top: 48px;
}
.benefit-item {
    background: var(--card-bg);
    border: 1px solid var(--border-light);
    border-radius: 14px;
    padding: 22px 18px;
    text-align: center;
    transition: all 0.3s;
}
.benefit-item:hover {
    border-color: var(--accent-purple);
    transform: translateY(-3px);
}
.benefit-item strong {
    display: block;
    color: var(--text-main);
    font-size: 15px;
    margin-bottom: 8px;
}
.benefit-item p {
    color: var(--text-muted);
    font-size: 13px;
    line-height: 1.65;
}

/* Four evaluation keys (AI content selection) */
.eval-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 20px;
    margin-top: 36px;
}
.eval-card {
    background: rgba(253, 86, 34, 0.06);
    border: 1px solid rgba(253, 86, 34, 0.2);
    border-radius: 14px;
    padding: 22px 18px;
    text-align: center;
}
.eval-card h4 {
    font-size: 15px;
    color: var(--accent-blue);
    font-weight: 700;
    margin-bottom: 10px;
}
.eval-card p {
    font-size: 13px;
    color: var(--text-muted);
    line-height: 1.65;
}

/* =========================================================
   FAQ (Accordion via <details>)
   ========================================================= */
.faq-list { max-width: 860px; margin: 0 auto; }
.faq-item {
    background: var(--card-bg);
    border: 1px solid var(--border-light);
    border-radius: 12px;
    margin-bottom: 14px;
    overflow: hidden;
    transition: border-color 0.3s;
}
.faq-item[open] { border-color: rgba(253, 86, 34, 0.4); }
.faq-item summary {
    cursor: pointer;
    list-style: none;
    padding: 20px 24px;
    font-weight: 600;
    font-size: 16px;
    color: var(--text-main);
    display: flex;
    justify-content: space-between;
    align-items: center;
    transition: background 0.2s;
}
.faq-item summary::-webkit-details-marker { display: none; }
.faq-item summary:hover { background: rgba(255, 255, 255, 0.02); }
.faq-item summary::after {
    content: '+';
    font-size: 22px;
    color: var(--accent-blue);
    font-weight: 300;
    margin-left: 16px;
    transition: transform 0.3s;
}
.faq-item[open] summary::after { content: '−'; }
.faq-answer {
    padding: 0 24px 22px;
    color: var(--text-muted);
    line-height: 1.8;
    font-size: 15px;
}
/* =========================================================
   Comparison (Chat Boxes)
   ========================================================= */
.comparison-wrapper {
    display: flex;
    gap: 30px;
    align-items: stretch;
}
.chat-box {
    flex: 1;
    background: var(--bg-chat);
    border: 1px solid var(--border-light);
    border-radius: 16px;
    overflow: hidden;
    display: flex;
    flex-direction: column;
}
.chat-box.optimized {
    border-color: rgba(253, 86, 34, 0.5);
    box-shadow: 0 0 40px rgba(253, 86, 34, 0.12);
}
.chat-header {
    padding: 16px 20px;
    background: rgba(0, 0, 0, 0.3);
    border-bottom: 1px solid var(--border-light);
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 14px;
}
.chat-header-brand { color: var(--accent-blue); font-weight: bold; }

.chat-body { padding: 30px 20px; display: flex; flex-direction: column; gap: 20px; flex: 1; }

.badge { font-size: 12px; padding: 4px 12px; border-radius: 20px; }
.badge-fail { background: rgba(255, 255, 255, 0.08); color: #ccc; }
.badge-success {
    background: rgba(253, 86, 34, 0.2);
    color: var(--accent-blue);
    border: 1px solid rgba(253, 86, 34, 0.4);
}

.msg { padding: 14px 18px; border-radius: 12px; max-width: 88%; font-size: 14px; line-height: 1.7; }
.msg-user {
    background: var(--bg-user-msg);
    color: #fff;
    align-self: flex-end;
    border-bottom-right-radius: 2px;
}
.msg-ai {
    background: rgba(255, 255, 255, 0.03);
    color: var(--text-chat);
    align-self: flex-start;
    border-bottom-left-radius: 2px;
    border: 1px solid var(--border-light);
}
.msg-ai.msg-ai-dim { opacity: 1; }

.msg-note { font-size: 12px; }
.msg-note-fail { color: var(--accent-blue); }
.msg-note-success { color: var(--accent-blue); }

.highlight-word { color: var(--accent-blue); font-weight: bold; }

/* =========================================================
   Coverage List
   ========================================================= */
.coverage-list {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 20px;
    list-style: none;
}
.coverage-list li {
    padding: 20px 40px;
    background: var(--card-bg);
    border: 1px solid var(--border-light);
    border-radius: 16px;
    color: var(--text-main);
    font-weight: 500;
    transition: all 0.3s;
}
.coverage-list li:hover {
    border-color: var(--accent-blue);
    transform: translateY(-3px);
    color: var(--accent-blue);
}

/* =========================================================
   Footer
   ========================================================= */
.site-footer {
    border-top: 1px solid var(--border-light);
    padding: 80px 0 40px;
    background: var(--bg-darker);
    text-align: center;
}
.footer-desc { color: var(--text-muted); margin-bottom: 30px; }
.footer-copy { margin-top: 40px; font-size: 14px; color: var(--text-dim); }

/* 仅版权信息的精简页脚 */
.site-footer--legal {
    padding: 32px 0 40px;
}
.site-footer--legal .footer-copy {
    margin-top: 0;
}

/* 返回顶部（固定在视口右下，滚动后出现） */
.back-to-top {
    position: fixed;
    right: 22px;
    bottom: 26px;
    z-index: 250;
    width: 46px;
    height: 46px;
    padding: 0;
    border: 1px solid var(--border-light);
    border-radius: 50%;
    background: rgba(17, 17, 17, 0.92);
    color: var(--accent-blue);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.35);
    -webkit-backdrop-filter: blur(8px);
            backdrop-filter: blur(8px);
    opacity: 0;
    visibility: hidden;
    transform: translateY(10px);
    transition: opacity 0.25s ease, visibility 0.25s ease, transform 0.25s ease,
                background 0.2s, color 0.2s, border-color 0.2s;
}
.back-to-top.is-visible {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}
.back-to-top:hover {
    background: rgba(45, 46, 61, 0.95);
    border-color: rgba(253, 86, 34, 0.35);
    color: #fff;
}
.back-to-top:focus-visible {
    outline: 2px solid var(--accent-blue);
    outline-offset: 3px;
}
.back-to-top svg {
    width: 22px;
    height: 22px;
    display: block;
}

@media (max-width: 1023px) {
    .back-to-top {
        right: 14px;
        bottom: calc(100px + env(safe-area-inset-bottom, 0px));
    }
}

/* =========================================================
   咨询二维码弹层
   ========================================================= */
.modal {
    position: fixed;
    inset: 0;
    z-index: 320;
    display: none;
    align-items: center;
    justify-content: center;
    padding: 24px;
}
.modal.is-open {
    display: flex;
}
.modal__backdrop {
    position: absolute;
    inset: 0;
    background: rgba(0, 0, 0, 0.65);
    cursor: pointer;
}
.modal__panel {
    position: relative;
    z-index: 1;
    max-width: min(92vw, 320px);
    padding: 28px 24px 22px;
    background: var(--bg-darker);
    border: 1px solid var(--border-light);
    border-radius: 16px;
    box-shadow: 0 24px 64px rgba(0, 0, 0, 0.55);
    text-align: center;
}
.modal__qr-wrap {
    position: relative;
    display: inline-block;
    margin: 0 auto;
    padding: 8px;
    background: #fff;
    border-radius: 12px;
}
.modal__qr {
    display: block;
    width: 240px;
    height: auto;
    max-width: 72vw;
    vertical-align: middle;
    border-radius: 8px;
}
.modal__close {
    position: absolute;
    top: -10px;
    right: -10px;
    width: 36px;
    height: 36px;
    padding: 0;
    border: none;
    border-radius: 50%;
    background: var(--bg-darker);
    color: var(--text-main);
    font-size: 22px;
    line-height: 1;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 4px 14px rgba(0, 0, 0, 0.35);
    border: 1px solid var(--border-light);
    transition: background 0.2s, color 0.2s;
}
.modal__close:hover {
    background: #2a2a2a;
    color: #fff;
}
.modal__close:focus-visible {
    outline: 2px solid var(--accent-blue);
    outline-offset: 2px;
}
.modal__title {
    margin-top: 16px;
    font-size: 15px;
    font-weight: 600;
    color: var(--text-muted);
}

/* =========================================================
   Animations
   ========================================================= */
.fade-in {
    opacity: 0;
    transform: translateY(20px);
    transition: opacity 0.8s, transform 0.8s;
}
.fade-in.visible {
    opacity: 1;
    transform: translateY(0);
}

/* =========================================================
   Responsive
   ========================================================= */
@media (max-width: 900px) {
    .grid-3 { grid-template-columns: 1fr; }
    .grid-2 { grid-template-columns: 1fr; }
    .comparison-wrapper { flex-direction: column; }
    .stats-grid { grid-template-columns: repeat(2, 1fr); }
    .methodology-grid { grid-template-columns: repeat(2, 1fr); }
    .benefit-grid { grid-template-columns: repeat(2, 1fr); }
    .eval-grid { grid-template-columns: repeat(2, 1fr); }
    .ai-flow { flex-direction: column; }
    .flow-arrow { transform: rotate(90deg); justify-content: center; padding: 4px 0; }
}

@media (max-width: 768px) {
    section { padding: 70px 0; }
    .hero { padding: 80px 0 60px; }
    .hero h1 { font-size: 36px; }
    .hero .hero-desc { font-size: 16px; }
    h2.section-title { font-size: 28px; }
    p.section-subtitle { font-size: 16px; margin-bottom: 40px; }

    .definition-card { padding: 28px 22px; }
    .definition-card p { font-size: 15px; }
    .stat-num { font-size: 30px; }
    .comparison-table th,
    .comparison-table td { padding: 14px 16px; font-size: 14px; }
    .faq-item summary { padding: 18px 20px; font-size: 15px; }
}

@media (max-width: 560px) {
    .stats-grid { grid-template-columns: 1fr; }
    .methodology-grid { grid-template-columns: 1fr; }
    .benefit-grid { grid-template-columns: 1fr; }
    .eval-grid { grid-template-columns: 1fr; }
}