:root {
    --ink: #1f3438;
    --muted: #6e8188;
    --teal: #2f898e;
    --teal-dark: #226e73;
    --pale: #f3f9fa;
    --aqua: #e8f5f6;
    --line: #d9e7e9;
    --white: #ffffff;
    --warm: #f8f5ef;
    --shadow: 0 20px 50px rgba(31, 71, 77, 0.09);
    --radius: 22px;
}

* {
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    margin: 0;
    color: var(--ink);
    background: var(--pale);
    font-family: "PingFang SC", "Microsoft YaHei", "Noto Sans CJK SC", Arial, sans-serif;
    font-size: 17px;
    line-height: 1.85;
    -webkit-font-smoothing: antialiased;
}

a {
    color: var(--teal-dark);
    text-underline-offset: 0.18em;
}

.skip-link {
    position: fixed;
    top: 12px;
    left: 12px;
    z-index: 100;
    padding: 9px 15px;
    color: #fff;
    background: var(--ink);
    border-radius: 999px;
    transform: translateY(-150%);
}

.skip-link:focus {
    transform: translateY(0);
}

.site-header {
    position: sticky;
    top: 0;
    z-index: 30;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 24px;
    min-height: 96px;
    padding: 14px clamp(18px, 5vw, 80px);
    background: rgba(255, 255, 255, 0.95);
    border-bottom: 1px solid var(--line);
    backdrop-filter: blur(14px);
}

.brand {
    display: inline-flex;
    align-items: center;
    gap: 16px;
    color: var(--ink);
    text-decoration: none;
}

.brand img {
    display: block;
    width: 96px;
    height: auto;
}

.brand-copy {
    display: grid;
    gap: 1px;
}

.brand-copy strong {
    color: var(--teal-dark);
    font-size: clamp(18px, 2.1vw, 26px);
    letter-spacing: 0.02em;
}

.brand-copy small {
    color: #819398;
    font-size: 13px;
    letter-spacing: 0.06em;
}

.header-links {
    display: flex;
    align-items: center;
    gap: 10px;
}

.header-links a {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-height: 44px;
    padding: 0 18px;
    font-size: 14px;
    font-weight: 750;
    text-decoration: none;
    border: 1px solid var(--line);
    border-radius: 999px;
}

.header-links a:last-child {
    color: #fff;
    background: var(--teal);
    border-color: var(--teal);
}

.page-shell {
    width: min(1160px, calc(100% - 36px));
    margin-inline: auto;
}

.breadcrumb {
    display: flex;
    flex-wrap: wrap;
    gap: 7px;
    padding: 26px 0 0;
    color: var(--muted);
    font-size: 14px;
}

.breadcrumb a {
    color: var(--muted);
    text-decoration: none;
}

.eyebrow {
    margin: 0 0 12px;
    color: var(--teal);
    font-size: 13px;
    font-weight: 800;
    letter-spacing: 0.17em;
}

.hub-hero,
.article-hero {
    padding: clamp(62px, 9vw, 112px) 0 clamp(48px, 7vw, 80px);
}

.hub-hero h1,
.article-hero h1 {
    max-width: 900px;
    margin: 0;
    font-size: clamp(42px, 6.4vw, 78px);
    line-height: 1.1;
    letter-spacing: -0.045em;
}

.hero-lead {
    max-width: 820px;
    margin: 28px 0 0;
    color: var(--muted);
    font-size: clamp(18px, 2.2vw, 24px);
}

.hero-meta {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    margin-top: 28px;
}

.hero-meta span,
.hero-meta time {
    padding: 7px 13px;
    color: var(--teal-dark);
    background: var(--aqua);
    border-radius: 999px;
    font-size: 13px;
    font-weight: 700;
}

.definition-box {
    margin: 0 0 42px;
    padding: clamp(24px, 4vw, 38px);
    background: var(--white);
    border: 1px solid var(--line);
    border-left: 5px solid var(--teal);
    border-radius: 0 var(--radius) var(--radius) 0;
    box-shadow: var(--shadow);
}

.definition-box strong {
    display: block;
    margin-bottom: 8px;
    color: var(--teal-dark);
    font-size: 15px;
}

.definition-box p {
    margin: 0;
    font-size: clamp(18px, 2.1vw, 22px);
}

.knowledge-map {
    margin-bottom: clamp(72px, 10vw, 120px);
    padding: clamp(28px, 5vw, 56px);
    color: #fff;
    background: var(--ink);
    border-radius: 32px;
    box-shadow: var(--shadow);
}

.knowledge-map h2 {
    margin: 0;
    font-size: clamp(30px, 4vw, 48px);
    line-height: 1.2;
}

.knowledge-map > p {
    max-width: 760px;
    margin: 14px 0 32px;
    color: #bdd0d3;
}

.entity-flow {
    display: grid;
    grid-template-columns: repeat(4, minmax(0, 1fr));
    gap: 12px;
    padding: 0;
    list-style: none;
}

.entity-flow li {
    position: relative;
    display: grid;
    align-content: center;
    min-height: 112px;
    padding: 20px;
    background: rgba(255, 255, 255, 0.08);
    border: 1px solid rgba(255, 255, 255, 0.15);
    border-radius: 16px;
}

.entity-flow li:first-child,
.entity-flow li:nth-child(2) {
    background: rgba(81, 178, 184, 0.2);
}

.entity-flow strong,
.entity-flow small {
    display: block;
}

.entity-flow small {
    margin-top: 5px;
    color: #bdd0d3;
}

.entity-legend {
    margin: 18px 0 0;
    color: #9fb7bb;
    font-size: 13px;
}

.section-heading {
    margin-bottom: 28px;
}

.section-heading h2 {
    margin: 0;
    font-size: clamp(32px, 5vw, 54px);
    line-height: 1.2;
}

.section-heading p {
    max-width: 760px;
    margin: 14px 0 0;
    color: var(--muted);
}

.topic-grid {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 18px;
    margin-bottom: clamp(76px, 10vw, 128px);
}

.topic-card {
    display: grid;
    align-content: start;
    min-height: 310px;
    padding: clamp(26px, 4vw, 38px);
    background: var(--white);
    border: 1px solid var(--line);
    border-top: 5px solid #75c0c5;
    border-radius: var(--radius);
    box-shadow: 0 14px 35px rgba(31, 71, 77, 0.06);
}

.topic-card .number {
    color: var(--teal);
    font-size: 14px;
    font-weight: 800;
    letter-spacing: 0.12em;
}

.topic-card h3 {
    margin: 22px 0 12px;
    font-size: clamp(25px, 3vw, 34px);
    line-height: 1.25;
}

.topic-card p {
    margin: 0;
    color: var(--muted);
}

.topic-card a {
    align-self: end;
    justify-self: start;
    margin-top: 26px;
    font-weight: 800;
    text-decoration: none;
}

.term-grid {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 14px;
    margin-bottom: clamp(72px, 9vw, 112px);
}

.term-grid article {
    padding: 24px;
    background: var(--aqua);
    border-radius: 16px;
}

.term-grid h3 {
    margin: 0 0 6px;
    font-size: 18px;
}

.term-grid p {
    margin: 0;
    color: var(--muted);
    font-size: 15px;
}

.article-layout {
    display: grid;
    grid-template-columns: minmax(0, 760px) minmax(220px, 1fr);
    align-items: start;
    gap: clamp(34px, 6vw, 76px);
    padding-bottom: clamp(80px, 10vw, 130px);
}

.article-body {
    min-width: 0;
    padding: clamp(30px, 5vw, 56px);
    background: var(--white);
    border: 1px solid var(--line);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
}

.article-body h2 {
    margin: 2.2em 0 0.6em;
    font-size: clamp(27px, 3.8vw, 38px);
    line-height: 1.3;
}

.article-body h2:first-child {
    margin-top: 0;
}

.article-body h3 {
    margin: 1.7em 0 0.45em;
    font-size: 22px;
    line-height: 1.4;
}

.article-body p,
.article-body ul,
.article-body ol {
    margin: 0 0 1.25em;
}

.article-body ul,
.article-body ol {
    padding-left: 1.4em;
}

.article-body li + li {
    margin-top: 0.6em;
}

.key-point,
.boundary-note,
.evidence-note {
    margin: 32px 0;
    padding: 24px 26px;
    border-radius: 16px;
}

.key-point {
    background: var(--aqua);
    border-left: 4px solid var(--teal);
}

.boundary-note {
    background: #fff6ee;
    border-left: 4px solid #c98645;
}

.evidence-note {
    background: var(--warm);
    border: 1px solid #e9e0d2;
}

.key-point strong,
.boundary-note strong,
.evidence-note strong {
    display: block;
    margin-bottom: 6px;
}

.key-point p,
.boundary-note p,
.evidence-note p {
    margin: 0;
}

.faq-list details {
    padding: 19px 0;
    border-top: 1px solid var(--line);
}

.faq-list details:last-child {
    border-bottom: 1px solid var(--line);
}

.faq-list summary {
    cursor: pointer;
    font-weight: 800;
}

.faq-list details p {
    margin: 12px 0 0;
    color: var(--muted);
}

.references {
    font-size: 14px;
    overflow-wrap: anywhere;
}

.references li + li {
    margin-top: 12px;
}

.article-aside {
    position: sticky;
    top: 118px;
    display: grid;
    gap: 16px;
}

.aside-card {
    padding: 22px;
    background: var(--white);
    border: 1px solid var(--line);
    border-radius: 16px;
}

.aside-card h2,
.aside-card h3 {
    margin: 0 0 12px;
    font-size: 17px;
}

.aside-card ul {
    margin: 0;
    padding: 0;
    list-style: none;
}

.aside-card li + li {
    margin-top: 10px;
}

.aside-card a {
    font-size: 14px;
    font-weight: 700;
    text-decoration: none;
}

.editorial-note {
    margin-bottom: 70px;
    padding: 28px;
    color: var(--muted);
    background: var(--white);
    border: 1px solid var(--line);
    border-radius: var(--radius);
    font-size: 15px;
}

.editorial-note h2 {
    margin: 0 0 8px;
    color: var(--ink);
    font-size: 20px;
}

.editorial-note p {
    margin: 0;
}

footer {
    display: flex;
    justify-content: space-between;
    gap: 20px;
    padding: 30px clamp(18px, 5vw, 80px);
    color: #74898e;
    background: #e8f2f3;
    font-size: 14px;
}

footer p {
    margin: 0;
}

@media (max-width: 880px) {
    .article-layout {
        grid-template-columns: 1fr;
    }

    .article-aside {
        position: static;
        grid-template-columns: repeat(2, minmax(0, 1fr));
    }

    .entity-flow,
    .term-grid {
        grid-template-columns: repeat(2, minmax(0, 1fr));
    }
}

@media (max-width: 640px) {
    body {
        font-size: 16px;
    }

    .site-header {
        min-height: 84px;
        padding: 10px 14px;
    }

    .brand {
        gap: 9px;
    }

    .brand img {
        width: 66px;
    }

    .brand-copy strong {
        font-size: 16px;
    }

    .brand-copy small {
        display: none;
    }

    .header-links a {
        min-height: 40px;
        padding: 0 11px;
        font-size: 12px;
    }

    .header-links a:first-child {
        display: none;
    }

    .page-shell {
        width: min(100% - 24px, 1160px);
    }

    .hub-hero h1,
    .article-hero h1 {
        font-size: clamp(39px, 12vw, 56px);
    }

    .entity-flow,
    .topic-grid,
    .term-grid,
    .article-aside {
        grid-template-columns: 1fr;
    }

    .topic-card {
        min-height: 270px;
    }

    .article-body {
        padding: 28px 20px;
    }

    footer {
        flex-direction: column;
    }
}

@media (prefers-reduced-motion: reduce) {
    html {
        scroll-behavior: auto;
    }
}

/*==========================================================
HEYOUQUAN Knowledge Mobile Typography Calibration
Scope  : Knowledge hub and articles, phone only (<= 640px)
Purpose: align mobile reading density with the official website
Added  : 2026-08-18
==========================================================*/

@media (max-width: 640px) {

    body {
        font-size: 16px;
        line-height: 1.8;
    }

    /* Header: retain brand recognition without forced wrapping */
    .site-header {
        gap: 10px;
        min-height: 78px;
        padding: 10px 12px;
    }

    .brand {
        flex: 0 1 auto;
        min-width: 0;
        gap: 8px;
    }

    .brand img {
        flex: 0 0 auto;
        width: 62px;
    }

    .brand-copy strong {
        max-width: 140px;
        font-size: 15px;
        line-height: 1.35;
        letter-spacing: 0.01em;
    }

    .header-links {
        flex: 0 0 auto;
        gap: 7px;
    }

    .header-links a {
        min-height: 40px;
        padding: 0 11px;
        font-size: 13px;
        line-height: 1;
        white-space: nowrap;
    }

    /* Page frame and breadcrumb */
    .page-shell {
        width: min(100% - 28px, 1160px);
    }

    .breadcrumb {
        padding-top: 22px;
        font-size: 13px;
    }

    .eyebrow {
        margin-bottom: 10px;
        font-size: 12px;
        line-height: 1.5;
        letter-spacing: 0.14em;
    }

    /* Knowledge hub and article hero */
    .hub-hero,
    .article-hero {
        padding: 46px 0 38px;
    }

    .hub-hero h1,
    .article-hero h1 {
        font-size: 36px;
        line-height: 1.2;
        letter-spacing: -0.025em;
    }

    .hero-lead,
    .article-hero .lead {
        max-width: 100%;
        margin: 20px 0 0;
        color: var(--muted);
        font-size: 17px;
        line-height: 1.8;
    }

    .hero-meta,
    .article-meta {
        display: flex;
        flex-wrap: wrap;
        gap: 8px;
        margin-top: 20px;
    }

    .hero-meta span,
    .hero-meta time,
    .article-meta span,
    .article-meta time {
        padding: 6px 11px;
        color: var(--teal-dark);
        background: var(--aqua);
        border-radius: 999px;
        font-size: 12px;
        font-weight: 700;
    }

    /* Knowledge hub hierarchy */
    .knowledge-map {
        margin-bottom: 64px;
        padding: 26px 22px;
        border-radius: 24px;
    }

    .knowledge-map h2,
    .section-heading h2 {
        font-size: 30px;
        line-height: 1.25;
    }

    .knowledge-map > p,
    .section-heading p {
        font-size: 16px;
        line-height: 1.8;
    }

    .section-heading {
        margin-bottom: 24px;
    }

    .topic-grid {
        gap: 18px;
        margin-bottom: 64px;
    }

    .topic-card {
        min-height: 0;
        padding: 28px 24px;
    }

    .topic-card .number {
        font-size: 13px;
    }

    .topic-card h3 {
        margin: 18px 0 10px;
        font-size: 24px;
        line-height: 1.35;
    }

    .topic-card p {
        font-size: 16px;
        line-height: 1.8;
    }

    .topic-card a {
        margin-top: 22px;
        font-size: 16px;
    }

    /* Definitions and article content */
    .definition-box {
        margin-bottom: 32px;
        padding: 22px 20px;
    }

    .definition-box strong {
        font-size: 15px;
    }

    .definition-box p {
        font-size: 16px;
        line-height: 1.8;
    }

    .article-layout {
        gap: 24px;
        padding-bottom: 64px;
    }

    .article-body {
        padding: 26px 20px;
    }

    .article-body h2 {
        margin: 2em 0 0.55em;
        font-size: 26px;
        line-height: 1.35;
    }

    .article-body h3 {
        font-size: 21px;
        line-height: 1.4;
    }

    .article-body p,
    .article-body ul,
    .article-body ol {
        font-size: 16px;
        line-height: 1.8;
    }

    .key-point,
    .boundary-note,
    .evidence-note {
        margin: 26px 0;
        padding: 20px 18px;
    }

    .key-point strong,
    .boundary-note strong,
    .evidence-note strong {
        font-size: 16px;
    }

    .article-aside,
    .article-layout > aside {
        position: static;
        display: grid;
        grid-template-columns: 1fr;
        gap: 14px;
    }

    .aside-card {
        padding: 20px;
    }

    footer {
        font-size: 13px;
        line-height: 1.7;
    }
}

@media (max-width: 380px) {

    .hub-hero h1,
    .article-hero h1 {
        font-size: 34px;
    }

    .knowledge-map h2,
    .section-heading h2 {
        font-size: 28px;
    }

    .header-links a {
        padding-inline: 9px;
        font-size: 12px;
    }
}