/* ============================================================
   platform-portal · 1XBET22-C20 深灰门户设计系统
   配色：#10151d 深灰蓝 / #0ea5e9 亮蓝 / 白
   Tailwind 负责基础工具类，本文件负责本站版式与组件。
   断点：375（移动基准） / 768 / 1024 / 1440
   ============================================================ */

:root {
    --ink: #10151d;
    --panel: #151d2b;
    --panel-2: #1b2537;
    --line: #26334b;
    --accent: #0ea5e9;
    --accent-deep: #0369a1;
    --text: #e9eef7;
    --muted: #9eafc6;
    --chip: #0c2438;
    --radius: 12px;
    --radius-lg: 16px;
    --shadow: 0 10px 30px rgba(4, 10, 20, .45);
}

* {
    box-sizing: border-box;
}

html,
body {
    margin: 0;
    padding: 0;
    overflow-x: hidden;
}

body {
    background: var(--ink);
    color: var(--text);
    font-family: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", system-ui, sans-serif;
    line-height: 1.75;
}

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

a {
    color: inherit;
    text-decoration: none;
}

figure {
    margin: 0;
}

.container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding-left: 16px;
    padding-right: 16px;
}

.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

/* ---------- 顶栏：分组导航 + 搜索视觉 ---------- */

.site-header {
    position: sticky;
    top: 0;
    z-index: 50;
    background: rgba(16, 21, 29, .96);
    border-bottom: 1px solid var(--line);
}

.site-header.scrolled {
    box-shadow: var(--shadow);
}

.header-row {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 14px;
    min-height: 64px;
}

.brand {
    display: flex;
    align-items: center;
    gap: 10px;
    flex: 0 0 auto;
}

.brand-badge {
    width: 38px;
    height: 38px;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    border-radius: 10px;
    background: linear-gradient(135deg, var(--accent), #38bdf8);
    color: #fff;
    font-size: 18px;
}

.brand-txt {
    display: flex;
    flex-direction: column;
    line-height: 1.2;
}

.brand-txt strong {
    font-size: 18px;
    letter-spacing: .5px;
    color: #fff;
}

.brand-txt small {
    font-size: 12px;
    color: var(--muted);
    letter-spacing: 1px;
}

.main-nav {
    display: flex;
    gap: 4px;
}

.main-nav a {
    padding: 8px 14px;
    border-radius: 8px;
    font-size: 15px;
    color: var(--muted);
    white-space: nowrap;
}

.main-nav a:hover {
    color: #fff;
    background: var(--panel-2);
}

.main-nav a[aria-current="page"] {
    color: #fff;
    background: var(--chip);
    box-shadow: inset 0 -2px 0 var(--accent);
}

.header-side {
    display: flex;
    align-items: center;
    gap: 10px;
    flex: 0 0 auto;
}

.search-visual {
    display: flex;
    align-items: center;
    gap: 8px;
    min-width: 190px;
    padding: 8px 14px;
    border: 1px solid var(--line);
    border-radius: 999px;
    color: var(--muted);
    font-size: 13px;
    background: var(--panel);
}

.search-visual i {
    color: var(--accent);
}

.nav-toggle {
    display: none;
    width: 44px;
    height: 44px;
    align-items: center;
    justify-content: center;
    border: 1px solid var(--line);
    border-radius: 10px;
    background: var(--panel);
    color: #fff;
    font-size: 18px;
    cursor: pointer;
}

/* ---------- 按钮 ---------- */

.btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 11px 22px;
    border-radius: 10px;
    font-size: 15px;
    font-weight: 600;
    line-height: 1.4;
    transition: transform .15s ease, box-shadow .15s ease;
    white-space: nowrap;
}

.btn-primary {
    background: linear-gradient(135deg, #0ea5e9, #38bdf8);
    color: #071018;
}

.btn-primary:hover {
    box-shadow: 0 8px 22px rgba(14, 165, 233, .35);
    transform: translateY(-1px);
}

.btn-ghost {
    border: 1px solid #38bdf8;
    color: #7dd3fc;
    background: transparent;
}

.btn-ghost:hover {
    background: rgba(14, 165, 233, .12);
}

/* ---------- 通用区块头与 overline ---------- */

.overline {
    margin: 0 0 10px;
    font-size: 12px;
    font-weight: 700;
    letter-spacing: 3px;
    color: var(--accent);
    text-transform: uppercase;
}

.section-head {
    margin-bottom: 26px;
}

.section-head h3,
.plain-faq h3,
.about-faq h3,
.catalog-faq h3,
.app-faq h3,
.device-zone h3 {
    margin: 0;
    font-size: 26px;
    line-height: 1.35;
    color: #fff;
}

/* ---------- Hero：小标签 + 标题 + 三张入口卡 ---------- */

.hero {
    padding: 46px 0 18px;
    background:
        radial-gradient(700px 320px at 85% -10%, rgba(14, 165, 233, .18), transparent 60%),
        var(--ink);
}

.hero-top {
    display: grid;
    grid-template-columns: 1fr;
    gap: 26px;
    align-items: center;
}

.hero-copy h2 {
    margin: 0 0 14px;
    font-size: clamp(1.7rem, 4vw, 2.6rem);
    line-height: 1.3;
    color: #fff;
}

.hero-sub {
    margin: 0 0 20px;
    max-width: 560px;
    color: var(--muted);
}

.hero-actions {
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
    margin-bottom: 18px;
}

.hero-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.hero-tags span {
    display: inline-block;
    padding: 4px 12px;
    border: 1px solid rgba(56, 189, 248, .45);
    border-radius: 999px;
    font-size: 13px;
    color: #7dd3fc;
    background: var(--chip);
}

.hero-figure img,
.split-figure img,
.dl-figure img,
.head-figure img,
.strip-figure img {
    width: 100%;
    aspect-ratio: 16 / 10;
    object-fit: cover;
    border-radius: var(--radius-lg);
    border: 1px solid var(--line);
    box-shadow: var(--shadow);
}

/* 三张大型入口卡 */

.entry-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 16px;
    margin-top: 34px;
    padding-bottom: 40px;
}

.entry-card {
    position: relative;
    padding: 24px;
    border: 1px solid var(--line);
    border-top: 3px solid var(--accent);
    border-radius: var(--radius);
    background: linear-gradient(180deg, var(--panel), var(--ink));
}

.entry-card::before {
    content: "";
    position: absolute;
    top: 14px;
    right: 14px;
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background: var(--accent);
    box-shadow: 0 0 10px rgba(14, 165, 233, .8);
}

.entry-icon {
    display: inline-flex;
    width: 46px;
    height: 46px;
    align-items: center;
    justify-content: center;
    border-radius: 12px;
    background: var(--chip);
    color: #38bdf8;
    font-size: 20px;
}

.entry-card h3 {
    margin: 14px 0 8px;
    font-size: 20px;
    color: #fff;
}

.entry-card p {
    margin: 6px 0;
    color: var(--muted);
    font-size: 14.5px;
}

.card-cta {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    margin-top: 10px;
    font-weight: 600;
    color: #7dd3fc;
}

.card-cta:hover {
    color: #fff;
}

/* ---------- 快速通道（6 图标列表，2 列） ---------- */

.quick-zone {
    padding: 34px 0;
    border-top: 1px solid var(--line);
}

.quick-grid {
    list-style: none;
    margin: 0;
    padding: 0;
    display: grid;
    grid-template-columns: 1fr;
    gap: 12px;
}

.quick-card {
    display: flex;
    gap: 14px;
    padding: 16px 18px;
    border: 1px solid var(--line);
    border-radius: var(--radius);
    background: var(--panel);
}

.quick-icon {
    flex: 0 0 auto;
    display: inline-flex;
    width: 40px;
    height: 40px;
    align-items: center;
    justify-content: center;
    border-radius: 10px;
    background: var(--chip);
    color: var(--accent);
    font-size: 17px;
}

.quick-card h4 {
    margin: 0 0 4px;
    font-size: 16px;
    color: #fff;
}

.quick-card p {
    margin: 0;
    font-size: 14px;
    color: var(--muted);
}

/* ---------- 体育 / 游戏模块：图文分栏 ---------- */

.module-split {
    padding: 40px 0;
    border-top: 1px solid var(--line);
}

.module-reverse {
    background: var(--panel);
}

.split-row {
    display: grid;
    grid-template-columns: 1fr;
    gap: 26px;
    align-items: center;
}

.module-copy h3 {
    margin: 0 0 12px;
    font-size: 25px;
    color: #fff;
}

.module-copy > p {
    color: var(--muted);
}

.spot-list {
    list-style: none;
    margin: 18px 0 0;
    padding: 0;
    display: grid;
    gap: 10px;
}

.spot-list li {
    display: flex;
    gap: 10px;
    align-items: flex-start;
    font-size: 15px;
    color: #c9d5e6;
}

.spot-list i {
    margin-top: 5px;
    color: var(--accent);
}

/* ---------- 下载与访问：说明 + 3 步骤卡 ---------- */

.dl-zone {
    padding: 40px 0;
    border-top: 1px solid var(--line);
}

.dl-intro {
    display: grid;
    grid-template-columns: 1fr;
    gap: 22px;
    align-items: center;
    margin-bottom: 26px;
}

.dl-intro h3 {
    margin: 0 0 10px;
    font-size: 25px;
    color: #fff;
}

.dl-intro p {
    margin: 0;
    color: var(--muted);
}

.steps-row {
    list-style: none;
    margin: 0;
    padding: 0;
    counter-reset: step;
    display: grid;
    grid-template-columns: 1fr;
    gap: 14px;
}

.step-card {
    position: relative;
    padding: 20px;
    border: 1px solid var(--line);
    border-radius: var(--radius);
    background: var(--panel);
}

.step-no {
    display: inline-flex;
    width: 30px;
    height: 30px;
    align-items: center;
    justify-content: center;
    margin-bottom: 10px;
    border-radius: 8px;
    background: linear-gradient(135deg, var(--accent), #38bdf8);
    color: #071018;
    font-weight: 700;
    font-size: 14px;
}

.step-card h4 {
    margin: 0 0 6px;
    font-size: 17px;
    color: #fff;
}

.step-card p {
    margin: 0;
    font-size: 14px;
    color: var(--muted);
}

/* ---------- 帮助速览（4 条迷你 FAQ） ---------- */

.assist-hub {
    padding: 40px 0 34px;
    border-top: 1px solid var(--line);
}

.mini-faq {
    display: grid;
    grid-template-columns: 1fr;
    gap: 10px;
}

/* ---------- details / summary 通用 ---------- */

details {
    border: 1px solid var(--line);
    border-radius: 10px;
    background: var(--panel);
    overflow: hidden;
}

details[open] {
    border-color: rgba(14, 165, 233, .5);
}

summary {
    padding: 14px 44px 14px 16px;
    position: relative;
    cursor: pointer;
    font-weight: 600;
    color: #dbe6f4;
    list-style: none;
}

summary::-webkit-details-marker {
    display: none;
}

summary::after {
    content: "+";
    position: absolute;
    right: 16px;
    top: 50%;
    transform: translateY(-50%);
    font-size: 18px;
    font-weight: 400;
    color: var(--accent);
}

details[open] summary::after {
    transform: translateY(-50%) rotate(45deg);
}

details p {
    margin: 0;
    padding: 0 16px 16px;
    color: var(--muted);
    font-size: 14.5px;
}

/* ---------- 用户声音 ---------- */

.voices {
    padding: 40px 0;
    border-top: 1px solid var(--line);
    background: var(--panel);
}

.voices-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 14px;
}

.voice-card {
    margin: 0;
    padding: 20px;
    border: 1px solid var(--line);
    border-left: 3px solid var(--accent);
    border-radius: var(--radius);
    background: var(--ink);
}

.voice-card p {
    margin: 0 0 10px;
    color: #c9d5e6;
    font-size: 15px;
}

.voice-card cite {
    color: var(--muted);
    font-size: 13px;
    font-style: normal;
}

/* ---------- FAQ：左右两列、主题小标题分组 ---------- */

.faq-zone {
    padding: 40px 0;
}

.faq-cols {
    display: grid;
    grid-template-columns: 1fr;
    gap: 26px;
}

.faq-col h4 {
    margin: 0 0 12px;
    display: inline-block;
    padding: 4px 14px;
    border-radius: 999px;
    background: var(--chip);
    border: 1px solid rgba(14, 165, 233, .35);
    color: #7dd3fc;
    font-size: 14px;
}

.faq-col details {
    margin-bottom: 10px;
}

/* ---------- 底部蓝色 CTA 卡 ---------- */

.final-cta {
    padding: 10px 0 46px;
}

.cta-card {
    padding: 34px 22px;
    text-align: center;
    border: 1px solid rgba(56, 189, 248, .4);
    border-radius: var(--radius-lg);
    background:
        radial-gradient(480px 200px at 50% -40px, rgba(14, 165, 233, .3), transparent 70%),
        var(--panel-2);
}

.cta-card h3 {
    margin: 0 0 8px;
    font-size: 24px;
    color: #fff;
}

.cta-card p {
    margin: 0 auto 18px;
    max-width: 560px;
    color: var(--muted);
}

.cta-actions {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 12px;
}

/* ---------- 页脚：深灰底、顶蓝细条、四列 ---------- */

.site-footer {
    border-top: 4px solid var(--accent);
    background: #0c111a;
}

.foot-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 24px;
    padding-top: 34px;
    padding-bottom: 26px;
}

.foot-h {
    margin: 0 0 12px;
    font-size: 14px;
    font-weight: 700;
    letter-spacing: 2px;
    color: #fff;
}

.foot-brand {
    display: inline-block;
    margin-bottom: 10px;
    font-weight: 700;
    color: #7dd3fc;
}

.foot-note {
    margin: 0;
    font-size: 13px;
    color: var(--muted);
}

.foot-links {
    list-style: none;
    margin: 0;
    padding: 0;
    display: grid;
    gap: 8px;
}

.foot-links a,
.friend-links a {
    font-size: 14px;
    color: var(--muted);
}

.foot-links a:hover,
.friend-links a:hover {
    color: #7dd3fc;
}

.friend-links {
    display: grid;
    gap: 8px;
}

.foot-legal {
    border-top: 1px solid var(--line);
    padding: 16px 0 22px;
}

.foot-legal p {
    margin: 0;
    font-size: 12.5px;
    color: #73839c;
}

/* ---------- 内页页头（图文分栏） ---------- */

.page-head {
    padding: 40px 0 24px;
    background:
        radial-gradient(600px 240px at 90% -20px, rgba(14, 165, 233, .14), transparent 60%),
        var(--ink);
}

.head-row {
    display: grid;
    grid-template-columns: 1fr;
    gap: 22px;
    align-items: center;
}

.head-copy h2 {
    margin: 0 0 12px;
    font-size: clamp(1.55rem, 3.4vw, 2.3rem);
    line-height: 1.35;
    color: #fff;
}

.head-copy > p {
    margin: 0;
    color: var(--muted);
}

.head-figure img {
    aspect-ratio: 4 / 3;
    max-height: 320px;
}

/* ---------- 内页通用：说明段、FAQ、内联 CTA ---------- */

.explain-block,
.about-faq,
.catalog-faq,
.app-faq {
    padding: 34px 0;
    border-top: 1px solid var(--line);
}

.explain-item {
    margin-bottom: 28px;
}

.explain-item h3,
.plain-faq h3 {
    margin: 0 0 10px;
    font-size: 21px;
    color: #fff;
}

.explain-item p {
    margin: 8px 0;
    color: var(--muted);
}

.tree-panel {
    margin-top: 14px;
    padding: 18px 20px;
    border: 1px solid var(--line);
    border-radius: var(--radius);
    background: var(--panel);
}

.tree-panel h4 {
    margin: 0 0 10px;
    font-size: 15px;
    color: #7dd3fc;
}

.tree,
.tree ul {
    list-style: none;
    margin: 0;
    padding-left: 18px;
}

.tree {
    padding-left: 0;
}

.tree li {
    position: relative;
    padding: 3px 0 3px 16px;
    font-size: 14.5px;
    color: #c9d5e6;
}

.tree li::before {
    content: "";
    position: absolute;
    left: 0;
    top: 16px;
    width: 10px;
    height: 1px;
    background: var(--accent);
}

.tree .t-node {
    color: #fff;
    font-weight: 600;
}

.tree .t-node i {
    margin-right: 6px;
    color: var(--accent);
    font-size: 13px;
}

.plain-faq details {
    margin-bottom: 10px;
}

.inline-cta {
    display: flex;
    flex-direction: column;
    gap: 14px;
    align-items: flex-start;
    margin-top: 26px;
    padding: 22px;
    border-radius: var(--radius);
    background: var(--panel-2);
    border: 1px solid var(--line);
}

.inline-cta p {
    margin: 0;
    color: #c9d5e6;
}

/* ---------- 模块目录页 ---------- */

.catalog-anchors {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-top: 16px;
}

.catalog-anchors a {
    padding: 7px 14px;
    border-radius: 999px;
    border: 1px solid var(--line);
    font-size: 13.5px;
    color: var(--muted);
    background: var(--panel);
}

.catalog-anchors a:hover {
    color: #fff;
    border-color: rgba(56, 189, 248, .6);
}

.catalog-zone {
    padding: 30px 0 6px;
}

.catalog-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 14px;
}

.catalog-card {
    display: flex;
    gap: 16px;
    padding: 20px;
    border: 1px solid var(--line);
    border-radius: var(--radius);
    background: var(--panel);
}

.cat-icon {
    flex: 0 0 auto;
    display: inline-flex;
    width: 48px;
    height: 48px;
    align-items: center;
    justify-content: center;
    border-radius: 12px;
    background: var(--chip);
    color: #38bdf8;
    font-size: 20px;
}

.cat-body h3 {
    margin: 0 0 6px;
    font-size: 18px;
    color: #fff;
}

.cat-status {
    display: inline-block;
    margin-left: 6px;
    padding: 1px 10px;
    vertical-align: 2px;
    border-radius: 999px;
    font-size: 12px;
    font-weight: 400;
    color: #7dd3fc;
    background: var(--chip);
    border: 1px solid rgba(14, 165, 233, .3);
}

.cat-body p {
    margin: 0;
    font-size: 14px;
    color: var(--muted);
}

.strip-zone {
    padding: 20px 0 10px;
}

.strip-figure img {
    aspect-ratio: 21 / 9;
    max-height: 280px;
}

.catalog-faq {
    padding-top: 10px;
}

/* ---------- 公告页 ---------- */

.news-zone {
    padding: 26px 0 20px;
}

.news-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 14px;
}

.news-card {
    display: flex;
    flex-direction: column;
    padding: 20px;
    border: 1px solid var(--line);
    border-radius: var(--radius);
    background: var(--panel);
}

.news-badge {
    align-self: flex-start;
    padding: 2px 12px;
    border-radius: 999px;
    font-size: 12px;
    font-weight: 600;
}

.badge-update {
    background: var(--chip);
    color: #7dd3fc;
}

.badge-note {
    background: rgba(34, 197, 94, .12);
    color: #86efac;
}

.badge-maint {
    background: rgba(250, 204, 21, .12);
    color: #fde047;
}

.badge-event {
    background: rgba(168, 85, 247, .16);
    color: #d8b4fe;
}

.badge-content {
    background: rgba(56, 189, 248, .12);
    color: #7dd3fc;
}

.badge-remind {
    background: rgba(248, 113, 113, .14);
    color: #fca5a5;
}

.news-card h3 {
    margin: 12px 0 8px;
    font-size: 18px;
    color: #fff;
}

.news-card p {
    margin: 0 0 12px;
    flex: 1 1 auto;
    font-size: 14px;
    color: var(--muted);
}

.news-time {
    font-size: 12.5px;
    color: #73839c;
}

/* ---------- 支持页：通道卡 + 分组 deck ---------- */

.channel-zone {
    padding: 30px 0 10px;
}

.channel-row {
    display: grid;
    grid-template-columns: 1fr;
    gap: 14px;
}

.channel-card {
    display: block;
    padding: 22px;
    border: 1px solid var(--line);
    border-top: 3px solid var(--accent);
    border-radius: var(--radius);
    background: var(--panel);
    transition: transform .15s ease;
}

.channel-card:hover {
    transform: translateY(-2px);
    border-color: rgba(56, 189, 248, .55);
}

.ch-icon {
    display: inline-flex;
    width: 44px;
    height: 44px;
    align-items: center;
    justify-content: center;
    border-radius: 12px;
    background: var(--chip);
    color: var(--accent);
    font-size: 19px;
}

.channel-card h3 {
    margin: 12px 0 6px;
    font-size: 18px;
    color: #fff;
}

.channel-card p {
    margin: 0;
    font-size: 14px;
    color: var(--muted);
}

.deck-zone {
    padding: 20px 0 44px;
}

.deck {
    display: grid;
    grid-template-columns: 1fr;
    gap: 16px;
}

.deck-group {
    padding: 18px;
    border: 1px solid var(--line);
    border-radius: var(--radius);
    background: var(--panel);
}

.deck-group h3 {
    margin: 0 0 12px;
    font-size: 18px;
    color: #7dd3fc;
}

.deck-group details {
    margin-bottom: 8px;
    background: var(--ink);
}

/* ---------- 访问入口页：4 步 + 两端说明 ---------- */

.guide-zone,
.device-zone,
.app-faq {
    padding: 30px 0;
}

.guide-steps {
    list-style: none;
    margin: 0;
    padding: 0;
    counter-reset: guide;
    display: grid;
    grid-template-columns: 1fr;
    gap: 14px;
}

.guide-step {
    position: relative;
    padding: 24px 20px 20px;
    border: 1px solid var(--line);
    border-radius: var(--radius);
    background: var(--panel);
}

.guide-no {
    position: absolute;
    top: -14px;
    left: 20px;
    display: inline-flex;
    width: 28px;
    height: 28px;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--accent), #38bdf8);
    color: #071018;
    font-weight: 700;
    font-size: 14px;
}

.guide-step > i {
    display: block;
    margin: 4px 0 10px;
    font-size: 24px;
    color: #38bdf8;
}

.guide-step h3 {
    margin: 0 0 8px;
    font-size: 18px;
    color: #fff;
}

.guide-step p {
    margin: 0;
    font-size: 14.5px;
    color: var(--muted);
}

.device-zone {
    border-top: 1px solid var(--line);
}

.device-row {
    display: grid;
    grid-template-columns: 1fr;
    gap: 14px;
}

.device-card {
    padding: 22px;
    border: 1px solid var(--line);
    border-radius: var(--radius);
    background: var(--panel);
}

.dev-icon {
    display: inline-flex;
    width: 44px;
    height: 44px;
    align-items: center;
    justify-content: center;
    border-radius: 12px;
    background: var(--chip);
    color: var(--accent);
    font-size: 19px;
}

.device-card h4 {
    margin: 12px 0 6px;
    font-size: 17px;
    color: #fff;
}

.device-card p {
    margin: 0;
    font-size: 14px;
    color: var(--muted);
}

/* ---------- 返回顶部 ---------- */

.to-top {
    position: fixed;
    right: 18px;
    bottom: 18px;
    z-index: 60;
    width: 44px;
    height: 44px;
    display: flex;
    align-items: center;
    justify-content: center;
    border: 1px solid rgba(56, 189, 248, .5);
    border-radius: 12px;
    background: var(--panel-2);
    color: #7dd3fc;
    font-size: 16px;
    cursor: pointer;
    opacity: 0;
    visibility: hidden;
    transition: opacity .2s ease, visibility .2s ease;
}

.to-top.visible {
    opacity: 1;
    visibility: visible;
}

/* ============================================================
   响应式：768 平板 / 1024 桌面 / 1440 宽屏
   ============================================================ */

@media (min-width: 768px) {
    .container {
        padding-left: 24px;
        padding-right: 24px;
    }

    .quick-grid {
        grid-template-columns: 1fr 1fr;
    }

    .mini-faq,
    .faq-cols {
        grid-template-columns: 1fr 1fr;
    }

    .news-grid,
    .catalog-grid {
        grid-template-columns: 1fr 1fr;
    }

    .deck {
        grid-template-columns: 1fr 1fr;
    }

    .foot-grid {
        grid-template-columns: 1fr 1fr;
    }
}

@media (min-width: 1024px) {
    .nav-toggle {
        display: none;
    }

    .main-nav {
        display: flex !important;
    }

    .hero-top,
    .split-row,
    .dl-intro,
    .head-row {
        grid-template-columns: 1.15fr 1fr;
    }

    .module-reverse .split-row {
        grid-template-columns: 1fr 1.15fr;
    }

    .module-reverse .split-figure {
        order: 1;
    }

    .module-reverse .module-copy {
        order: 2;
    }

    .entry-grid,
    .voices-grid,
    .channel-row,
    .device-row,
    .steps-row {
        grid-template-columns: repeat(3, 1fr);
    }

    .foot-grid {
        grid-template-columns: 1fr 1fr 1fr 1.2fr;
    }

    .news-grid {
        grid-template-columns: repeat(3, 1fr);
    }

    .guide-steps {
        grid-template-columns: repeat(4, 1fr);
    }
}

@media (min-width: 1440px) {
    .container {
        max-width: 1280px;
        padding-left: 32px;
        padding-right: 32px;
    }

    .hero-copy h2 {
        font-size: 2.6rem;
    }
}

/* 窄屏导航折叠面板（1023px 以下生效） */

@media (max-width: 1023px) {
    .main-nav {
        display: none;
        position: absolute;
        top: 64px;
        left: 0;
        right: 0;
        flex-direction: column;
        gap: 2px;
        padding: 10px 16px 16px;
        background: rgba(16, 21, 29, .99);
        border-bottom: 1px solid var(--line);
    }

    .main-nav.open {
        display: flex;
    }

    .main-nav a {
        padding: 12px 14px;
        border-radius: 8px;
    }

    .nav-toggle {
        display: inline-flex;
    }

    .search-visual {
        display: none;
    }
}