:root {
    --paper: #f8f6f1;
    --paper-strong: #fffefa;
    --ink: #0a1424;
    --ink-soft: #42516a;
    --line: #d9dde5;
    --line-strong: #b8c1d0;
    --blue: #0868f7;
    --blue-dark: #064ec4;
    --cyan: #24c9ef;
    --coral: #ff6f47;
    --green: #18785b;
    --max: 1400px;
    --radius-s: 12px;
    --radius-m: 22px;
    --radius-l: 36px;
    --shadow: 0 24px 80px rgba(15, 32, 62, .10);
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
    margin: 0;
    color: var(--ink);
    background: var(--paper);
    font-family: "Microsoft YaHei UI", "PingFang SC", "Noto Sans CJK SC", system-ui, sans-serif;
    font-size: 16px;
    line-height: 1.72;
    text-rendering: optimizeLegibility;
    -webkit-font-smoothing: antialiased;
}

body::before {
    content: "";
    position: fixed;
    inset: 0;
    pointer-events: none;
    opacity: .16;
    background-image: url("images/qidian-hero-devices.webp");
    background-size: 1px 1px;
    z-index: -1;
}

img { display: block; max-width: 100%; }
a { color: inherit; text-decoration: none; }
button, input, textarea, select { font: inherit; }
button, a { -webkit-tap-highlight-color: transparent; }

:focus-visible {
    outline: 3px solid rgba(8, 104, 247, .38);
    outline-offset: 4px;
}

.skip-link {
    position: fixed;
    left: 16px;
    top: -80px;
    z-index: 1000;
    padding: 10px 16px;
    border-radius: 999px;
    color: white;
    background: var(--blue);
}

.skip-link:focus { top: 16px; }

.site-shell {
    width: min(calc(100% - 48px), var(--max));
    margin-inline: auto;
}

.narrow-shell { max-width: 920px; }

.site-header {
    position: sticky;
    top: 0;
    z-index: 100;
    border-bottom: 1px solid transparent;
    background: rgba(248, 246, 241, .92);
    backdrop-filter: blur(18px);
    transition: border-color .2s ease, box-shadow .2s ease;
}

.site-header.is-scrolled {
    border-color: rgba(10, 20, 36, .08);
    box-shadow: 0 8px 30px rgba(10, 20, 36, .05);
}

.nav-shell {
    min-height: 82px;
    display: grid;
    grid-template-columns: auto 1fr auto;
    align-items: center;
    gap: 34px;
}

.brand {
    display: inline-flex;
    align-items: center;
    gap: 12px;
    white-space: nowrap;
}

.brand img {
    width: 46px;
    height: 46px;
    border-radius: 13px;
    object-fit: cover;
}

.brand span {
    display: flex;
    align-items: baseline;
    gap: 8px;
    letter-spacing: -.02em;
}

.brand strong { font-size: 24px; line-height: 1; }
.brand b { font-size: 17px; font-weight: 700; }

.site-nav {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 34px;
}

.site-nav a {
    position: relative;
    color: #263349;
    font-size: 15px;
    font-weight: 650;
}

.site-nav a::after {
    content: "";
    position: absolute;
    left: 0;
    right: 0;
    bottom: -12px;
    height: 2px;
    background: var(--blue);
    transform: scaleX(0);
    transform-origin: center;
    transition: transform .2s ease;
}

.site-nav a:hover::after,
.site-nav a[aria-current="page"]::after { transform: scaleX(1); }

.nav-cta,
.button {
    min-height: 50px;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    border: 1px solid var(--blue);
    border-radius: 999px;
    padding: 0 26px;
    color: white;
    background: var(--blue);
    font-weight: 750;
    line-height: 1.2;
    cursor: pointer;
    transition: transform .2s ease, background .2s ease, box-shadow .2s ease;
}

.nav-cta:hover,
.button:hover {
    background: var(--blue-dark);
    box-shadow: 0 12px 30px rgba(8, 104, 247, .22);
    transform: translateY(-2px);
}

.button.secondary {
    color: var(--ink);
    border-color: var(--ink);
    background: transparent;
}

.button.secondary:hover {
    color: white;
    background: var(--ink);
    box-shadow: none;
}

.button.disabled,
.button[aria-disabled="true"] {
    color: #68748a;
    border-color: #cfd4dc;
    background: #e8e8e6;
    box-shadow: none;
    pointer-events: none;
}

.menu-button { display: none; }

.hero {
    overflow: hidden;
    padding: 48px 0 26px;
}

.hero-grid {
    display: grid;
    grid-template-columns: minmax(430px, .9fr) minmax(560px, 1.1fr);
    align-items: start;
    gap: 24px;
}

.eyebrow {
    margin: 0 0 18px;
    color: var(--blue);
    font-size: 14px;
    font-weight: 800;
    letter-spacing: .14em;
    text-transform: uppercase;
}

.hero h1,
.page-hero h1 {
    margin: 0;
    letter-spacing: -.055em;
    line-height: 1.04;
}

.hero h1 { font-size: clamp(54px, 6.5vw, 104px); }

.hero h1 .brand-line {
    display: flex;
    align-items: baseline;
    gap: 20px;
    margin-bottom: 22px;
}

.hero h1 .brand-line small {
    font-size: .43em;
    letter-spacing: -.04em;
}

.hero h1 .headline-line {
    display: block;
    font-size: .46em;
    letter-spacing: -.045em;
    line-height: 1.18;
    white-space: nowrap;
}

.platform-line {
    margin: 22px 0 0;
    color: var(--blue);
    font-size: clamp(19px, 2vw, 27px);
    font-weight: 750;
    letter-spacing: -.02em;
}

.hero-summary {
    max-width: 620px;
    margin: 22px 0 0;
    color: var(--ink-soft);
    font-size: 18px;
}

.hero-actions,
.section-actions {
    display: flex;
    flex-wrap: wrap;
    gap: 14px;
    margin-top: 30px;
}

.hero-visual {
    position: relative;
    margin-top: -44px;
    margin-right: -5vw;
}

.hero-visual img {
    width: 100%;
    height: 520px;
    max-height: 680px;
    object-fit: contain;
    mix-blend-mode: multiply;
}

.process-rail {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    margin-top: 20px;
    border: 1px solid var(--line);
    border-radius: var(--radius-m);
    background: rgba(255, 254, 250, .7);
}

.process-step {
    display: grid;
    grid-template-columns: auto 1fr;
    gap: 16px;
    padding: 24px 28px;
}

.process-step + .process-step { border-left: 1px solid var(--line); }
.process-step span { color: var(--blue); font-size: 27px; font-weight: 500; }
.process-step h2 { margin: 1px 0 4px; font-size: 18px; }
.process-step p { margin: 0; color: var(--ink-soft); font-size: 14px; }

.section {
    padding: 108px 0;
}

.section.compact { padding: 72px 0; }
.section.white { background: var(--paper-strong); }
.section.dark { color: white; background: var(--ink); }

.section-heading {
    display: grid;
    grid-template-columns: minmax(0, 1.1fr) minmax(320px, .7fr);
    align-items: end;
    gap: 48px;
    margin-bottom: 48px;
}

.section-heading h2,
.download-intro h2,
.cta-panel h2 {
    max-width: 900px;
    margin: 0;
    font-size: clamp(38px, 5vw, 72px);
    line-height: 1.12;
    letter-spacing: -.045em;
}

.section-heading p,
.download-intro p {
    margin: 0;
    color: var(--ink-soft);
    font-size: 17px;
}

.section.dark .section-heading p { color: #bfc9d8; }

.feature-list {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    border-top: 1px solid var(--line);
}

.feature-row {
    min-height: 190px;
    padding: 32px 36px 34px 0;
    border-bottom: 1px solid var(--line);
}

.feature-row:nth-child(even) {
    padding-left: 36px;
    border-left: 1px solid var(--line);
}

.feature-row .index {
    display: block;
    margin-bottom: 30px;
    color: var(--blue);
    font-size: 14px;
    font-weight: 800;
}

.feature-row h3 { margin: 0 0 10px; font-size: 25px; }
.feature-row p { max-width: 550px; margin: 0; color: var(--ink-soft); }

.image-frame {
    overflow: hidden;
    border-radius: var(--radius-l);
    background: #f2eee7;
    box-shadow: var(--shadow);
}

.image-frame img { width: 100%; height: 100%; object-fit: cover; }

.case-preview {
    display: grid;
    grid-template-columns: 1.25fr .75fr;
    gap: 28px;
    align-items: stretch;
}

.case-preview .image-frame { min-height: 520px; }

.case-copy {
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    padding: 26px 0 10px;
}

.case-tags { display: grid; gap: 0; }

.case-tags a {
    display: grid;
    grid-template-columns: 56px 1fr;
    gap: 18px;
    align-items: center;
    padding: 21px 0;
    border-bottom: 1px solid var(--line);
}

.case-tags b { color: var(--blue); font-size: 14px; }
.case-tags strong { font-size: 20px; }
.case-copy > p { color: var(--ink-soft); }

.download-intro {
    display: grid;
    grid-template-columns: 1fr auto;
    align-items: end;
    gap: 40px;
    margin-bottom: 36px;
}

.platform-downloads {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    border-top: 1px solid var(--line);
    border-bottom: 1px solid var(--line);
}

.platform-item {
    display: flex;
    min-height: 170px;
    flex-direction: column;
    justify-content: space-between;
    gap: 26px;
    padding: 28px 30px;
}

.platform-item + .platform-item { border-left: 1px solid var(--line); }

.platform-item h3 { margin: 0; font-size: 27px; }
.platform-item p { margin: 7px 0 0; color: var(--ink-soft); font-size: 14px; }
.platform-item a,
.platform-item .status { color: var(--blue); font-weight: 800; }
.platform-item .status { color: #657087; }

.page-hero {
    padding: 100px 0 72px;
    border-bottom: 1px solid var(--line);
}

.page-hero h1 { max-width: 900px; font-size: clamp(46px, 7vw, 92px); }
.page-lead { max-width: 760px; margin: 26px 0 0; color: var(--ink-soft); font-size: 20px; }

.split {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 70px;
    align-items: center;
}

.split.reverse .split-copy { order: 2; }
.split.reverse .image-frame { order: 1; }

.split-copy h2 { margin: 0 0 20px; font-size: clamp(34px, 4vw, 58px); line-height: 1.14; letter-spacing: -.04em; }
.split-copy > p { color: var(--ink-soft); font-size: 17px; }
.split-copy ul { padding: 0; margin: 28px 0 0; list-style: none; }
.split-copy li { padding: 16px 0; border-top: 1px solid var(--line); }
.split-copy li:last-child { border-bottom: 1px solid var(--line); }
.split-copy li strong { display: block; margin-bottom: 4px; }
.split-copy li span { color: var(--ink-soft); font-size: 14px; }

.principle-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 1px;
    background: var(--line);
    border: 1px solid var(--line);
}

.principle-card { min-height: 310px; padding: 36px; background: var(--paper); }
.principle-card b { color: var(--blue); font-size: 13px; letter-spacing: .12em; }
.principle-card h2,
.principle-card h3 { margin: 58px 0 14px; font-size: 27px; line-height: 1.25; }
.principle-card p { margin: 0; color: var(--ink-soft); }

.timeline { max-width: 980px; margin: 0 auto; }

.timeline-step {
    display: grid;
    grid-template-columns: 130px 1fr;
    gap: 30px;
    padding: 42px 0;
    border-top: 1px solid var(--line);
}

.timeline-step:last-child { border-bottom: 1px solid var(--line); }
.timeline-step .time { color: var(--blue); font-size: 14px; font-weight: 800; }
.timeline-step h2 { margin: 0 0 12px; font-size: 30px; }
.timeline-step p { margin: 0; color: var(--ink-soft); }

.use-case-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 1px;
    border: 1px solid var(--line);
    background: var(--line);
}

.use-case-card { min-height: 330px; padding: 42px; background: var(--paper-strong); }
.use-case-card b { color: var(--coral); font-size: 14px; }
.use-case-card h2 { margin: 72px 0 14px; font-size: 32px; }
.use-case-card p { margin: 0; color: var(--ink-soft); }

.notice {
    padding: 22px 24px;
    border-left: 4px solid var(--blue);
    color: var(--ink-soft);
    background: #edf4ff;
}

.notice strong { color: var(--ink); }

.download-visual {
    max-width: 1180px;
    margin: 0 auto 60px;
}

.download-visual img { width: 100%; mix-blend-mode: multiply; }

.platform-tabs {
    display: flex;
    gap: 8px;
    margin-bottom: 28px;
    border-bottom: 1px solid var(--line);
}

.platform-tab {
    min-width: 150px;
    padding: 15px 20px;
    border: 0;
    border-bottom: 3px solid transparent;
    color: var(--ink-soft);
    background: transparent;
    font-weight: 750;
    cursor: pointer;
}

.platform-tab.is-active { color: var(--blue); border-bottom-color: var(--blue); }

.download-panel {
    display: grid;
    grid-template-columns: 1fr minmax(300px, .65fr);
    gap: 60px;
    align-items: start;
    padding: 38px 0 0;
}

.download-panel[hidden] { display: none; }
.download-panel h2 { margin: 0 0 12px; font-size: 38px; }
.download-panel p { color: var(--ink-soft); }

.release-data { margin: 30px 0; border-top: 1px solid var(--line); }
.release-data div { display: grid; grid-template-columns: 120px 1fr; gap: 18px; padding: 13px 0; border-bottom: 1px solid var(--line); }
.release-data dt { color: var(--ink-soft); }
.release-data dd { margin: 0; font-weight: 650; overflow-wrap: anywhere; }

.checksum {
    padding: 22px;
    border-radius: var(--radius-s);
    background: #edf1f5;
}

.checksum.spaced { margin-top: 18px; }
.legal-link { color: var(--blue); font-weight: 750; }

.checksum code { display: block; overflow-wrap: anywhere; color: #1e3558; font-size: 13px; }
.text-button { padding: 0; border: 0; color: var(--blue); background: transparent; font-weight: 800; cursor: pointer; }

.requirements { padding: 28px; border: 1px solid var(--line); border-radius: var(--radius-m); }
.requirements h3 { margin-top: 0; }
.requirements ul { padding-left: 20px; margin-bottom: 0; color: var(--ink-soft); }

.help-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 20px;
}

.help-link {
    min-height: 220px;
    padding: 30px;
    border: 1px solid var(--line);
    border-radius: var(--radius-m);
    background: var(--paper-strong);
    transition: transform .2s ease, border-color .2s ease;
}

.help-link:hover { border-color: var(--blue); transform: translateY(-4px); }
.help-link b { color: var(--blue); font-size: 13px; }
.help-link h2 { margin: 56px 0 8px; font-size: 24px; }
.help-link p { margin: 0; color: var(--ink-soft); font-size: 14px; }

.article-shell {
    display: grid;
    grid-template-columns: 220px minmax(0, 760px);
    justify-content: center;
    gap: 70px;
}

.article-nav { position: sticky; top: 110px; align-self: start; display: grid; gap: 8px; }
.article-nav a { padding: 8px 0; color: var(--ink-soft); font-size: 14px; }
.article-nav a:hover { color: var(--blue); }
.article h2 { scroll-margin-top: 120px; margin: 62px 0 18px; font-size: 32px; }
.article h2:first-child { margin-top: 0; }
.article h3 { margin: 34px 0 12px; font-size: 21px; }
.article p,
.article li { color: var(--ink-soft); }
.article ol,
.article ul { padding-left: 24px; }
.article li + li { margin-top: 10px; }

.faq-list { max-width: 920px; margin: 0 auto; border-top: 1px solid var(--line); }
.faq-item { border-bottom: 1px solid var(--line); }
.faq-item button { width: 100%; display: flex; justify-content: space-between; gap: 30px; padding: 26px 0; border: 0; color: var(--ink); background: transparent; text-align: left; font-size: 19px; font-weight: 750; cursor: pointer; }
.faq-item button::after { content: "+"; color: var(--blue); font-size: 26px; font-weight: 400; }
.faq-item.is-open button::after { content: "−"; }
.faq-answer { display: none; max-width: 760px; padding: 0 0 26px; color: var(--ink-soft); }
.faq-item.is-open .faq-answer { display: block; }

.cta-panel {
    display: flex;
    align-items: flex-end;
    justify-content: space-between;
    gap: 50px;
    padding: 56px;
    border-radius: var(--radius-l);
    color: white;
    background: var(--ink);
}

.cta-panel h2 { max-width: 740px; font-size: clamp(36px, 5vw, 64px); }
.cta-panel p { max-width: 640px; margin: 18px 0 0; color: #bac5d5; }
.cta-panel .button { flex: none; }

.site-footer { padding: 76px 0 24px; border-top: 1px solid var(--line); background: #efede8; }
.footer-main { display: grid; grid-template-columns: 1fr 1.4fr; gap: 80px; }
.footer-brand p { max-width: 360px; margin: 20px 0 0; color: var(--ink-soft); }
.footer-links { display: grid; grid-template-columns: repeat(3, 1fr); gap: 36px; }
.footer-links section { display: grid; align-content: start; gap: 10px; }
.footer-links h2 { margin: 0 0 8px; font-size: 14px; }
.footer-links a { color: var(--ink-soft); font-size: 14px; }
.footer-links a:hover { color: var(--blue); }
.footer-bottom { display: flex; justify-content: space-between; gap: 30px; margin-top: 62px; padding-top: 22px; border-top: 1px solid var(--line); color: #69758a; font-size: 12px; }

@media (max-width: 1080px) {
    .nav-shell { grid-template-columns: auto auto 1fr; }
    .menu-button {
        display: inline-flex;
        justify-self: end;
        padding: 9px 14px;
        border: 1px solid var(--line-strong);
        border-radius: 999px;
        color: var(--ink);
        background: transparent;
        cursor: pointer;
    }
    .site-nav {
        position: absolute;
        left: 24px;
        right: 24px;
        top: 72px;
        display: none;
        align-items: stretch;
        flex-direction: column;
        gap: 0;
        padding: 14px;
        border: 1px solid var(--line);
        border-radius: var(--radius-m);
        background: var(--paper-strong);
        box-shadow: var(--shadow);
    }
    .site-nav.is-open { display: flex; }
    .site-nav a { padding: 12px 10px; }
    .site-nav a::after { display: none; }
    .nav-cta { justify-self: end; }
    .hero-grid { grid-template-columns: 1fr; }
    .hero-copy { max-width: 780px; }
    .hero-visual { width: min(900px, 100%); margin: 0 auto; }
    .hero-visual img { height: auto; }
    .section-heading { grid-template-columns: 1fr; }
    .case-preview { grid-template-columns: 1fr; }
    .case-preview .image-frame { min-height: 420px; }
    .case-tags { grid-template-columns: repeat(2, 1fr); }
    .case-tags a:nth-child(odd) { padding-right: 20px; }
    .split { gap: 40px; }
    .principle-grid { grid-template-columns: repeat(2, 1fr); }
    .help-grid { grid-template-columns: repeat(2, 1fr); }
}

@media (max-width: 760px) {
    .site-shell { width: min(calc(100% - 32px), var(--max)); }
    .nav-shell { min-height: 70px; grid-template-columns: 1fr auto; gap: 12px; }
    .brand img { width: 40px; height: 40px; border-radius: 11px; }
    .brand strong { font-size: 21px; }
    .brand b { display: none; }
    .nav-cta { display: none; }
    .hero { padding-top: 54px; }
    .hero h1 { font-size: clamp(52px, 19vw, 76px); }
    .hero h1 .brand-line { gap: 12px; margin-bottom: 18px; }
    .hero h1 .brand-line small { font-size: .35em; }
    .hero h1 .headline-line { font-size: .43em; line-height: 1.26; letter-spacing: -.03em; }
    .hero-summary { font-size: 16px; }
    .hero-actions .button { width: 100%; }
    .hero h1 .headline-line { white-space: normal; }
    .hero-visual { margin-top: 12px; }
    .process-rail { grid-template-columns: 1fr; }
    .process-step + .process-step { border-left: 0; border-top: 1px solid var(--line); }
    .section { padding: 76px 0; }
    .section.compact { padding: 54px 0; }
    .section-heading { gap: 18px; margin-bottom: 34px; }
    .section-heading h2,
    .download-intro h2,
    .cta-panel h2 { font-size: 38px; }
    .feature-list { grid-template-columns: 1fr; }
    .feature-row,
    .feature-row:nth-child(even) { min-height: auto; padding: 28px 0; border-left: 0; }
    .feature-row .index { margin-bottom: 18px; }
    .case-preview .image-frame { min-height: 280px; }
    .case-tags { grid-template-columns: 1fr; }
    .download-intro { grid-template-columns: 1fr; align-items: start; }
    .platform-downloads { grid-template-columns: 1fr; }
    .platform-item + .platform-item { border-left: 0; border-top: 1px solid var(--line); }
    .page-hero { padding: 72px 0 54px; }
    .page-hero h1 { font-size: 49px; }
    .page-lead { font-size: 17px; }
    .split,
    .download-panel { grid-template-columns: 1fr; }
    .split.reverse .split-copy,
    .split.reverse .image-frame { order: initial; }
    .principle-grid,
    .use-case-grid { grid-template-columns: 1fr; }
    .principle-card,
    .use-case-card { min-height: 260px; padding: 30px; }
    .principle-card h2,
    .principle-card h3,
    .use-case-card h2 { margin-top: 44px; }
    .timeline-step { grid-template-columns: 1fr; gap: 8px; padding: 32px 0; }
    .platform-tabs { overflow-x: auto; }
    .platform-tab { min-width: 120px; }
    .help-grid { grid-template-columns: 1fr; }
    .article-shell { grid-template-columns: 1fr; gap: 28px; }
    .article-nav { position: static; display: flex; overflow-x: auto; padding-bottom: 10px; }
    .article-nav a { flex: none; padding-right: 20px; }
    .cta-panel { align-items: stretch; flex-direction: column; padding: 34px 28px; }
    .footer-main { grid-template-columns: 1fr; gap: 44px; }
    .footer-links { gap: 20px; }
    .footer-bottom { flex-direction: column; }
}

@media (prefers-reduced-motion: reduce) {
    *, *::before, *::after { scroll-behavior: auto !important; transition: none !important; }
}