/* =========================================================
   2026 International Conference on Energy and Fuels
   style.css — 独立样式表（PC / 平板 / 手机自适应）
   内容严格来自会议 flyer 文档，样式参考 WCETC 官网风格
   ========================================================= */

/* ---------- 设计变量 ---------- */
:root {
    /* 品牌色取自会议 logo：深蓝 + 绿色 */
    --navy:        #0b3a75;
    --navy-dark:   #06264f;
    --blue:        #1565c0;
    --blue-light:  #4a90d9;
    --green:       #2f8f2a;

    --ink:         #1e2a3a;
    --ink-soft:    #3f566e;
    --muted:       #6b8299;

    --bg:          #f4f7fb;
    --surface:     #ffffff;
    --surface-alt: #f8fbff;
    --line:        #dfe7f1;
    --line-soft:   #eaf0f7;

    --radius-sm: 8px;
    --radius:    14px;
    --radius-lg: 20px;
    --radius-pill: 999px;

    --shadow-sm: 0 2px 6px rgba(6, 38, 79, .05);
    --shadow:    0 8px 22px rgba(6, 38, 79, .08);

    --header-h: 68px;
    --maxw: 1140px;

    --font: 'Segoe UI', -apple-system, BlinkMacSystemFont, Roboto,
            'Helvetica Neue', 'PingFang SC', 'Microsoft YaHei', sans-serif;
}

/* ---------- 全局重置 ---------- */
*,
*::before,
*::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
    -webkit-text-size-adjust: 100%;
}

body {
    font-family: var(--font);
    background-color: var(--bg);
    color: var(--ink);
    line-height: 1.7;
    font-size: 16px;
    overflow-x: hidden;
    -webkit-font-smoothing: antialiased;
}

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

a {
    color: var(--blue);
    text-decoration: none;
    transition: color .18s ease;
}

a:hover {
    color: var(--navy);
    text-decoration: underline;
}

/* 跳转链接 / 焦点样式 */
.skip-link {
    position: absolute;
    left: -9999px;
    top: 0;
    z-index: 200;
    background: var(--navy);
    color: #fff;
    padding: 10px 18px;
    border-radius: 0 0 var(--radius-sm) 0;
}

.skip-link:focus {
    left: 0;
    color: #fff;
}

:focus-visible {
    outline: 3px solid var(--blue-light);
    outline-offset: 2px;
}

/* =========================================================
   顶部导航
   ========================================================= */
.topbar {
    position: sticky;
    top: 0;
    z-index: 100;
    background: rgba(255, 255, 255, .94);
    backdrop-filter: saturate(160%) blur(10px);
    -webkit-backdrop-filter: saturate(160%) blur(10px);
    border-bottom: 1px solid var(--line);
    transition: box-shadow .2s ease;
}

.topbar.is-stuck {
    box-shadow: 0 4px 18px rgba(6, 38, 79, .10);
}

.topbar-inner {
    max-width: var(--maxw);
    margin: 0 auto;
    min-height: var(--header-h);
    padding: 8px 20px;
    display: flex;
    align-items: center;
    gap: 14px;
    flex-wrap: wrap;
}

/* 品牌 */
.brand {
    display: flex;
    align-items: center;
    gap: 10px;
    flex: 0 0 auto;
    margin-right: auto;
}

.brand:hover {
    text-decoration: none;
}

.brand img {
    height: 40px;
    width: auto;
}

.brand-text {
    display: flex;
    flex-direction: column;
    line-height: 1.25;
}

.brand-text strong {
    font-size: .98rem;
    font-weight: 700;
    color: var(--navy);
    letter-spacing: .2px;
}

.brand-text small {
    font-size: .75rem;
    color: var(--muted);
    font-weight: 500;
}

/* 菜单 */
.nav-menu {
    display: flex;
    align-items: center;
    flex-wrap: wrap;
    gap: 2px;
    list-style: none;
}

.nav-menu a {
    display: block;
    padding: 7px 10px;
    border-radius: var(--radius-pill);
    font-size: .88rem;
    font-weight: 500;
    color: #24435f;
    white-space: nowrap;
    transition: background .16s ease, color .16s ease;
}

.nav-menu a:hover {
    background: #e7f0fa;
    color: var(--navy);
    text-decoration: none;
}

.nav-menu a.is-active {
    background: var(--navy);
    color: #fff;
}

/* 汉堡按钮（窄屏） */
.nav-toggle {
    display: none;
    width: 42px;
    height: 38px;
    border: 1px solid var(--line);
    border-radius: var(--radius-sm);
    background: #fff;
    cursor: pointer;
    padding: 9px;
    flex-direction: column;
    justify-content: space-between;
}

.nav-toggle span {
    display: block;
    height: 2px;
    width: 100%;
    background: var(--navy);
    border-radius: 2px;
    transition: transform .22s ease, opacity .18s ease;
}

.nav-toggle.is-open span:nth-child(1) {
    transform: translateY(8px) rotate(45deg);
}

.nav-toggle.is-open span:nth-child(2) {
    opacity: 0;
}

.nav-toggle.is-open span:nth-child(3) {
    transform: translateY(-8px) rotate(-45deg);
}

/* =========================================================
   HERO
   ========================================================= */
.hero {
    position: relative;
    overflow: hidden;
    background: linear-gradient(160deg, #eaf3fd 0%, #f4f9f2 55%, #fdf6ec 100%);
    border-bottom: 1px solid var(--line);
}

.hero-bg {
    position: absolute;
    inset: 0;
    pointer-events: none;
    background:
        radial-gradient(60% 70% at 12% 18%, rgba(21, 101, 192, .16), transparent 62%),
        radial-gradient(55% 65% at 88% 24%, rgba(47, 143, 42, .16), transparent 60%),
        radial-gradient(45% 55% at 70% 92%, rgba(239, 139, 34, .12), transparent 62%);
}

.hero-bg::after {
    content: "";
    position: absolute;
    left: 0;
    right: 0;
    bottom: -1px;
    height: 90px;
    background:
        url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 1440 90' preserveAspectRatio='none'><path d='M0,52 C220,96 420,10 720,40 C1010,68 1220,96 1440,52 L1440,90 L0,90 Z' fill='%23f4f7fb'/></svg>")
        bottom center / 100% 100% no-repeat;
}

.hero-inner {
    position: relative;
    max-width: 880px;
    margin: 0 auto;
    padding: 54px 20px 46px;
    text-align: center;
}

.hero-logo {
    width: min(560px, 100%);
    margin: 0 auto 22px;
    mix-blend-mode: multiply;
}

.hero h1 {
    font-size: clamp(1.5rem, 3.6vw, 2.4rem);
    line-height: 1.28;
    font-weight: 700;
    color: var(--navy);
    letter-spacing: .2px;
    margin-bottom: 16px;
}

.hero-date {
    display: inline-block;
    font-size: clamp(1rem, 2vw, 1.22rem);
    font-weight: 700;
    color: #fff;
    background: linear-gradient(90deg, var(--navy) 0%, var(--blue) 55%, var(--green) 100%);
    padding: 7px 24px;
    border-radius: var(--radius-pill);
    margin-bottom: 14px;
    box-shadow: var(--shadow-sm);
}

.hero-venue {
    font-size: 1.02rem;
    color: var(--ink-soft);
    max-width: 640px;
    margin: 0 auto;
}

/* =========================================================
   主体布局
   ========================================================= */
.container {
    max-width: var(--maxw);
    margin: 0 auto;
    padding: 8px 20px 20px;
}

.section {
    background: var(--surface);
    border: 1px solid var(--line);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-sm);
    padding: 30px 34px 34px;
    margin: 26px 0;
    scroll-margin-top: calc(var(--header-h) + 16px);
}

.section-title {
    font-size: clamp(1.25rem, 2.4vw, 1.6rem);
    font-weight: 700;
    color: var(--navy);
    letter-spacing: .3px;
    padding-bottom: 12px;
    margin-bottom: 20px;
    position: relative;
}

.section-title::after {
    content: "";
    position: absolute;
    left: 0;
    bottom: 0;
    width: 68px;
    height: 4px;
    border-radius: 3px;
    background: linear-gradient(90deg, var(--navy), var(--green));
}

/* 正文段落 */
.body-text {
    font-size: 1.04rem;
    color: var(--ink-soft);
}

/* =========================================================
   人员列表（Co-Chairs / Organising Committee）
   要点列表（Travel / Accommodation）共用同一套视觉
   ========================================================= */
.people-list,
.fact-list {
    list-style: none;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: 0 28px;
}

.fact-list-single {
    grid-template-columns: 1fr;
}

.people-list li,
.fact-list li {
    position: relative;
    padding: 10px 0 10px 20px;
    border-bottom: 1px dashed #dde7f2;
}

.people-list li::before,
.fact-list li::before {
    content: "";
    position: absolute;
    left: 2px;
    top: 19px;
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background: var(--green);
}

.p-name,
.f-label {
    display: block;
    font-weight: 600;
    color: #16324f;
    font-size: 1rem;
}

.p-org,
.f-text {
    display: block;
    font-size: .89rem;
    color: var(--muted);
}

/* 单行要点（无副标题时正文用常规字号） */
.fact-list li > .f-text:only-child {
    font-size: .99rem;
    color: var(--ink-soft);
}

/* =========================================================
   Program
   ========================================================= */
.program-list {
    list-style: none;
    display: grid;
    gap: 12px;
}

.program-list li {
    display: grid;
    grid-template-columns: 300px 1fr;
    gap: 18px;
    align-items: center;
    background: var(--surface-alt);
    border: 1px solid var(--line);
    border-left: 5px solid var(--blue);
    border-radius: var(--radius);
    padding: 13px 20px;
}

.program-list li:nth-child(even) {
    border-left-color: var(--green);
}

.pg-time {
    font-weight: 700;
    color: var(--navy);
    font-size: .98rem;
}

.pg-desc {
    font-size: 1rem;
    color: var(--ink-soft);
}

/* =========================================================
   Key Dates
   ========================================================= */
.date-list {
    list-style: none;
    display: grid;
    gap: 12px;
}

.date-list-after {
    margin-top: 18px;
}

.date-list li {
    display: grid;
    grid-template-columns: 210px 1fr;
    gap: 18px;
    align-items: center;
    background: var(--surface-alt);
    border: 1px solid var(--line);
    border-left: 5px solid var(--blue);
    border-radius: var(--radius);
    padding: 14px 20px;
}

.date-list li.d-highlight {
    border-left-color: var(--green);
    background: #f2faf0;
}

.d-date {
    font-weight: 700;
    color: var(--navy);
    font-size: 1.02rem;
    white-space: nowrap;
}

.d-text {
    font-size: .99rem;
    color: var(--ink-soft);
}

.d-text a {
    font-weight: 600;
    word-break: break-word;
}

/* 费用表 */
.table-wrap {
    margin-top: 18px;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    border-radius: var(--radius);
}

.fee-table {
    width: 100%;
    border-collapse: separate;
    border-spacing: 0;
    min-width: 300px;
    background: #fff;
    border: 1px solid var(--line);
    border-radius: var(--radius);
    overflow: hidden;
}

.fee-table th {
    background: linear-gradient(135deg, var(--navy), #14508f);
    color: #fff;
    font-size: .98rem;
    font-weight: 700;
    padding: 13px 16px;
    text-align: center;
    border-right: 1px solid rgba(255, 255, 255, .18);
}

.fee-table th:last-child {
    border-right: none;
    background: linear-gradient(135deg, #1f7a2e, var(--green));
}

.fee-table td {
    padding: 20px 16px;
    text-align: center;
    border-right: 1px solid var(--line-soft);
}

.fee-table td:last-child {
    border-right: none;
}

.fee {
    font-size: clamp(1.3rem, 3vw, 1.65rem);
    font-weight: 700;
    color: var(--navy);
    letter-spacing: .5px;
}

.fee-table td:last-child .fee {
    color: #1f7a2e;
}

/* =========================================================
   Contact
   ========================================================= */
.info-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 22px;
}

.info-card {
    background: var(--surface-alt);
    padding: 20px 22px 22px;
    border-radius: var(--radius);
    border: 1px solid var(--line);
    box-shadow: var(--shadow-sm);
}

.info-card h3 {
    font-size: 1.08rem;
    font-weight: 700;
    color: var(--navy);
    border-bottom: 2px solid #cfdcec;
    padding-bottom: 9px;
    margin-bottom: 12px;
    letter-spacing: .2px;
}

.info-card p {
    font-size: .98rem;
    margin-bottom: 6px;
}

.info-card a {
    word-break: break-word;
}

/* =========================================================
   Abstract —— 模板下载
   ========================================================= */
.download-card {
    margin-top: 20px;
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    justify-content: space-between;
    gap: 16px;
    background: var(--surface-alt);
    border: 1px solid var(--line);
    border-left: 5px solid var(--green);
    border-radius: var(--radius);
    padding: 18px 22px;
}

.dl-info {
    display: flex;
    flex-direction: column;
    line-height: 1.5;
}

.dl-name {
    font-weight: 700;
    font-size: 1.02rem;
    color: var(--navy);
}

.dl-meta {
    font-size: .86rem;
    color: var(--muted);
}

.btn-download {
    flex: 0 0 auto;
    display: inline-flex;
    align-items: center;
    gap: 9px;
    padding: 11px 24px;
    border-radius: var(--radius-pill);
    background: linear-gradient(135deg, var(--navy), #14508f);
    color: #fff;
    font-size: .95rem;
    font-weight: 600;
    box-shadow: var(--shadow-sm);
    transition: background .18s ease, box-shadow .18s ease, transform .18s ease;
}

.btn-download:hover {
    background: linear-gradient(135deg, #1f7a2e, var(--green));
    color: #fff;
    text-decoration: none;
    transform: translateY(-1px);
    box-shadow: var(--shadow);
}

.dl-icon {
    font-size: 1.05rem;
    line-height: 1;
}

/* =========================================================
   Travel / Accommodation
   ========================================================= */
/* 分步骤条目（Transportation Options） */
.step-list {
    list-style: none;
    display: grid;
    gap: 12px;
}

.step-list li {
    background: var(--surface-alt);
    border: 1px solid var(--line);
    border-left: 5px solid var(--blue);
    border-radius: var(--radius);
    padding: 16px 20px 18px;
}

.step-list li:nth-child(even) {
    border-left-color: var(--green);
}

.st-title {
    display: block;
    font-weight: 700;
    color: var(--navy);
    font-size: 1rem;
    margin-bottom: 8px;
}

.st-num {
    display: inline-block;
    min-width: 24px;
    height: 24px;
    line-height: 24px;
    margin-right: 9px;
    border-radius: 50%;
    background: var(--navy);
    color: #fff;
    font-size: .82rem;
    text-align: center;
}

.step-list li:nth-child(even) .st-num {
    background: var(--green);
}

.st-text {
    display: block;
    font-size: .99rem;
    color: var(--ink-soft);
}

.st-text + .st-text {
    margin-top: 10px;
}

/* 小标题（章节内的二级标题） */
.sub-title {
    font-size: 1.06rem;
    font-weight: 700;
    color: var(--navy);
    margin: 26px 0 12px;
}

/* 章节内块级元素的衔接间距 */
.info-grid + .body-text,
.figure-grid + .sub-title {
    margin-top: 22px;
}

.body-text + .fact-list {
    margin-top: 12px;
}

/* 图片 + 图注 */
.figure-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    align-items: stretch;
    gap: 22px;
    margin-top: 22px;
}

.figure {
    display: flex;
    flex-direction: column;
    background: var(--surface-alt);
    border: 1px solid var(--line);
    border-radius: var(--radius);
    box-shadow: var(--shadow-sm);
    overflow: hidden;
}

.figure img {
    width: 100%;
    aspect-ratio: 3 / 2;
    object-fit: cover;
    object-position: center;
    border-bottom: 1px solid var(--line);
}

.figure figcaption {
    flex: 1 0 auto;
    font-size: .85rem;
    color: var(--muted);
    text-align: center;
    padding: 10px 14px 12px;
}

/* 提示条 */
.note {
    margin-top: 22px;
    background: #f2faf0;
    border: 1px solid #cfe6cb;
    border-left: 5px solid var(--green);
    border-radius: var(--radius);
    padding: 14px 20px 16px;
    font-size: .99rem;
    color: var(--ink-soft);
}

.note strong {
    color: #1f7a2e;
}

.note p {
    margin: 0;
}

.note p + p {
    margin-top: 10px;
}

/* =========================================================
   页脚
   ========================================================= */
.site-footer {
    margin-top: 30px;
    background: var(--navy-dark);
    color: #cfdcea;
}

.footer-inner {
    max-width: var(--maxw);
    margin: 0 auto;
    padding: 30px 20px;
    text-align: center;
}

.footer-inner p {
    font-size: .93rem;
    margin-bottom: 4px;
}

.footer-title {
    font-size: 1.05rem !important;
    font-weight: 700;
    color: #fff;
    margin-bottom: 10px !important;
}

/* 回到顶部 */
.to-top {
    position: fixed;
    right: 18px;
    bottom: 18px;
    z-index: 90;
    width: 44px;
    height: 44px;
    border-radius: 50%;
    background: var(--navy);
    color: #fff;
    font-size: 1.25rem;
    line-height: 44px;
    text-align: center;
    box-shadow: var(--shadow);
    opacity: 0;
    visibility: hidden;
    transform: translateY(10px);
    transition: opacity .2s ease, transform .2s ease, visibility .2s ease;
}

.to-top.is-visible {
    opacity: .92;
    visibility: visible;
    transform: translateY(0);
}

.to-top:hover {
    background: var(--blue);
    color: #fff;
    opacity: 1;
    text-decoration: none;
}

/* =========================================================
   响应式
   ========================================================= */

/* 窄屏：折叠菜单（导航项较多，1080px 起即折叠） */
@media (max-width: 1080px) {
    :root {
        --header-h: 60px;
    }

    .nav-toggle {
        display: flex;
    }

    .topbar-inner {
        padding: 8px 16px;
        row-gap: 0;
    }

    /* 让 .nav-menu 直接成为 .topbar-inner 的弹性子项，
       这样下面的 order / width 才会生效 */
    .topbar-inner nav {
        display: contents;
    }

    .nav-menu {
        display: none;
        flex-direction: column;
        align-items: stretch;
        gap: 2px;
        width: 100%;
        order: 3;
        padding: 8px 0 12px;
        border-top: 1px solid var(--line-soft);
        margin-top: 6px;
        max-height: calc(100vh - var(--header-h) - 20px);
        overflow-y: auto;
    }

    .nav-menu.is-open {
        display: flex;
    }

    .nav-menu a {
        padding: 11px 14px;
        font-size: 1rem;
        border-radius: var(--radius-sm);
    }
}

/* 平板及以下：内容布局收紧 */
@media (max-width: 880px) {
    .container {
        padding: 4px 14px 14px;
    }

    .section {
        padding: 24px 20px 26px;
        margin: 20px 0;
        border-radius: var(--radius);
    }

    .hero-inner {
        padding: 36px 18px 40px;
    }

    .hero-bg::after {
        height: 55px;
    }

    /* Program 上下堆叠 */
    .program-list li {
        grid-template-columns: 1fr;
        gap: 2px;
        padding: 13px 16px;
    }

    /* Key Dates 上下堆叠 */
    .date-list li {
        grid-template-columns: 1fr;
        gap: 4px;
        padding: 13px 16px;
    }
}

/* 手机 */
@media (max-width: 560px) {
    body {
        font-size: 15.5px;
    }

    .brand img {
        height: 34px;
    }

    .brand-text strong {
        font-size: .9rem;
    }

    .brand-text small {
        font-size: .7rem;
    }

    .hero-inner {
        padding: 28px 16px 34px;
    }

    .hero-logo {
        margin-bottom: 18px;
    }

    .hero-date {
        padding: 6px 16px;
    }

    .hero-venue {
        font-size: .95rem;
    }

    .section {
        padding: 20px 16px 22px;
    }

    .section-title {
        margin-bottom: 18px;
    }

    .people-list,
    .fact-list,
    .figure-grid,
    .info-grid {
        grid-template-columns: 1fr;
    }

    .info-card {
        padding: 16px 16px 18px;
    }

    .step-list li,
    .note {
        padding: 14px 16px 16px;
    }

    .download-card {
        flex-direction: column;
        align-items: stretch;
        padding: 16px;
    }

    .btn-download {
        justify-content: center;
    }

    .fee-table th {
        font-size: .88rem;
        padding: 12px 10px;
    }

    .fee-table td {
        padding: 16px 10px;
    }

    .to-top {
        right: 12px;
        bottom: 12px;
        width: 40px;
        height: 40px;
        line-height: 40px;
    }
}

/* 极窄屏 */
@media (max-width: 360px) {
    .brand-text {
        display: none;
    }
}

/* 大屏 */
@media (min-width: 1400px) {
    :root {
        --maxw: 1220px;
    }
}

/* 尊重"减少动效"偏好 */
@media (prefers-reduced-motion: reduce) {
    html {
        scroll-behavior: auto;
    }

    *,
    *::before,
    *::after {
        transition-duration: .01ms !important;
        animation-duration: .01ms !important;
    }
}

/* 打印 */
@media print {
    .topbar,
    .to-top,
    .nav-toggle {
        display: none !important;
    }

    body {
        background: #fff;
    }

    .section {
        box-shadow: none;
        border-color: #ccc;
        page-break-inside: avoid;
    }
}