/* ===== 习思·单词速记 子站样式（习思集团 AI英语 旗下项目） ===== */
:root {
    --primary: #1a5f7a;
    --primary-dark: #134b61;
    --accent: #e8903f;
    --accent-light: #f0a85c;
    --violet: #6c63ce;
    --ink: #22232e;
    --text-body: #4a4a5a;
    --text-light: #8a8a96;
    --paper: #f6f8fb;
    --paper-deep: #eaf1f7;
    --white: #ffffff;
    --shadow: 0 4px 18px rgba(19, 75, 97, 0.08);
    --shadow-hover: 0 14px 34px rgba(19, 75, 97, 0.16);
    --radius: 14px;
    --radius-lg: 22px;
    --c-teach: #2e7fa8;
    --c-learn: #55a868;
    --c-review: #dd8452;
    --c-parent: #8172b3;
}
* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
    font-family: 'Noto Sans SC', -apple-system, BlinkMacSystemFont, 'PingFang SC', 'Microsoft YaHei', sans-serif;
    color: var(--ink);
    background: var(--paper);
    line-height: 1.7;
    overflow-x: hidden;
    -webkit-text-size-adjust: 100%;
    text-size-adjust: 100%;
}
img { max-width: 100%; display: block; }
a { text-decoration: none; color: inherit; }
.container { max-width: 1120px; margin: 0 auto; padding: 0 24px; }

/* ---- 顶部导航 ---- */
.sj-nav {
    position: sticky; top: 0; z-index: 50;
    background: rgba(246, 248, 251, 0.92);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid rgba(34,35,46,0.08);
}
.sj-nav-inner { display: flex; align-items: center; justify-content: space-between; height: 62px; }
.sj-logo { display: flex; align-items: center; gap: 10px; font-size: 20px; font-weight: 800; color: var(--primary-dark); }
.sj-logo img { width: 38px; height: 38px; border-radius: 10px; object-fit: contain; background: #2E7FA8; }
.sj-logo small { font-size: 12px; color: var(--text-light); font-weight: 500; }
.sj-links { display: flex; align-items: center; gap: 6px; }
.sj-links a {
    padding: 8px 16px; border-radius: 999px; font-size: 15px; color: var(--text-body);
    transition: all .25s;
}
.sj-links a:hover { background: var(--paper-deep); color: var(--primary-dark); }
.sj-links a.active { background: var(--primary); color: #fff; }
.sj-links a.home-link { border: 1px solid rgba(26,95,122,.35); color: var(--primary); }
.sj-toggle { display: none; background: none; border: none; font-size: 24px; cursor: pointer; color: var(--primary-dark); }

/* ---- 面包屑 ---- */
.crumb { padding: 18px 0 0; font-size: 13.5px; color: var(--text-light); }
.crumb a { color: var(--primary); }
.crumb a:hover { text-decoration: underline; }

/* ---- 页面头 ---- */
.page-head { padding: 34px 0 10px; }
.page-head .eyebrow {
    display: inline-block; font-size: 13px; letter-spacing: 2px; color: var(--accent);
    font-weight: 700; margin-bottom: 8px;
}
.page-head h1 { font-size: 34px; color: var(--primary-dark); line-height: 1.3; }
.page-head p.sub { margin-top: 10px; color: var(--text-body); max-width: 780px; }

/* ---- 首页 Hero ---- */
.hero {
    position: relative; overflow: hidden;
    background: linear-gradient(160deg, #123a4e 0%, #1a5f7a 46%, #2d8fb0 100%);
    color: #fff;
    display: flex; flex-direction: column;
    min-height: calc(100vh - 62px);
}
.hero-inner { position: relative; z-index: 2; padding: 56px 0 6px; }
.hero .badge {
    display: inline-block; padding: 6px 16px; border-radius: 999px;
    background: rgba(232,144,63,.18); border: 1px solid rgba(240,168,92,.5);
    color: #ffd9ae; font-size: 14px; margin-bottom: 18px;
}
.hero h1 { font-size: 46px; line-height: 1.25; letter-spacing: 1px; }
.hero h1 .hl { color: var(--accent-light); }
.hero .slogan { margin-top: 14px; font-size: 16.5px; color: rgba(255,255,255,.88); max-width: 680px; }
.hero-feats { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 22px; }
.hero-feats span {
    padding: 7px 16px; border-radius: 999px; font-size: 13.5px;
    background: rgba(255,255,255,.1); border: 1px solid rgba(255,255,255,.22);
    color: rgba(255,255,255,.92);
}
.hero-center { position: relative; z-index: 2; flex: 1; display: flex; align-items: center; }
.hero-center .container { width: 100%; }
.hero-quote {
    position: relative; z-index: 2;
    border-top: 1px solid rgba(255,255,255,.16);
    padding: 20px 0 30px; text-align: center;
}
.hero-quote p { font-size: 19px; font-weight: 700; letter-spacing: 1px; color: #ffe9d2; }
.hero-quote small { display: block; margin-top: 4px; font-size: 13px; color: rgba(255,255,255,.6); font-weight: 400; letter-spacing: 0; }

/* ---- 数据条 ---- */
.stats-strip { display: flex; flex-wrap: wrap; gap: 14px; padding: 34px 0 8px; }
.stats-strip .stat {
    flex: 1; min-width: 140px;
    background: var(--white); border: 1px solid rgba(26,95,122,.14);
    border-radius: var(--radius); padding: 16px 22px;
    box-shadow: var(--shadow);
}
.stats-strip .stat b { display: block; font-size: 26px; color: var(--primary); }
.stats-strip .stat span { font-size: 13px; color: var(--text-body); }

/* ---- 入口大卡 ---- */
.entry-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px; padding: 26px 0 56px; }
.entry-card {
    position: relative; display: flex; flex-direction: column;
    border-radius: var(--radius-lg); overflow: hidden;
    background: var(--white); box-shadow: var(--shadow);
    transition: transform .3s, box-shadow .3s;
}
.entry-card:hover { transform: translateY(-6px); box-shadow: var(--shadow-hover); }
.ec-band { height: 8px; }
.ec-sys .ec-band { background: linear-gradient(90deg, var(--c-teach), #57b6dd); }
.ec-tech .ec-band { background: linear-gradient(90deg, var(--c-learn), #8fd0a0); }
.ec-method .ec-band { background: linear-gradient(90deg, var(--c-review), #f0b083); }
.ec-body { padding: 26px 24px 24px; display: flex; flex-direction: column; flex: 1; }
.ec-body .ec-icon { font-size: 34px; margin-bottom: 10px; }
.ec-body h2 { font-size: 22px; color: var(--primary-dark); }
.ec-body .ec-sub { margin-top: 8px; font-size: 14px; color: var(--text-body); flex: 1; }
.ec-tags { display: flex; flex-wrap: wrap; gap: 6px; margin-top: 14px; }
.ec-tags span {
    font-size: 12px; padding: 3px 10px; border-radius: 999px;
    background: var(--paper-deep); color: var(--primary-dark);
}
.ec-go { margin-top: 16px; font-size: 14px; font-weight: 700; color: var(--accent); }

/* ---- 四端系统 ---- */
.duan-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 26px; padding: 26px 0 20px; }
.duan-card {
    background: var(--white); border-radius: var(--radius-lg);
    box-shadow: var(--shadow); padding: 28px 26px; position: relative; overflow: hidden;
    transition: transform .3s, box-shadow .3s;
}
.duan-card:hover { transform: translateY(-4px); box-shadow: var(--shadow-hover); }
.duan-card::before {
    content: ''; position: absolute; left: 0; top: 0; bottom: 0; width: 6px;
    background: var(--dc, var(--primary));
}
.duan-card .dc-tag {
    display: inline-block; font-size: 12.5px; font-weight: 700; letter-spacing: 2px;
    color: var(--dc, var(--primary)); margin-bottom: 8px;
}
.duan-card h2 { font-size: 24px; color: var(--ink); }
.duan-card .dc-desc { margin-top: 6px; font-size: 14px; color: var(--text-light); }
.duan-card ul { list-style: none; margin-top: 16px; display: flex; flex-direction: column; gap: 10px; }
.duan-card li {
    position: relative; padding-left: 24px; font-size: 15px; color: var(--text-body);
}
.duan-card li::before {
    content: '✓'; position: absolute; left: 0; top: 0;
    color: var(--dc, var(--primary)); font-weight: 800;
}
.d-teach { --dc: var(--c-teach); }
.d-learn { --dc: var(--c-learn); }
.d-review { --dc: var(--c-review); }
.d-parent { --dc: var(--c-parent); }

/* ---- 学习闭环流程 ---- */
.flow-wrap { padding: 30px 0 56px; }
.flow-wrap h2.sec-title { font-size: 26px; color: var(--primary-dark); margin-bottom: 6px; }
.flow-wrap p.sec-sub { color: var(--text-body); font-size: 14.5px; margin-bottom: 22px; }
.flow-line { display: flex; align-items: stretch; gap: 0; flex-wrap: wrap; }
.flow-step {
    flex: 1; min-width: 160px; position: relative;
    background: var(--white); border-radius: var(--radius);
    box-shadow: var(--shadow); padding: 20px 18px 18px; margin: 8px 14px 8px 0;
    text-align: center;
}
.flow-step .fs-no {
    width: 38px; height: 38px; margin: 0 auto 10px; border-radius: 50%;
    background: linear-gradient(135deg, var(--primary), #2d8fb0);
    color: #fff; font-weight: 800; font-size: 17px;
    display: flex; align-items: center; justify-content: center;
}
.flow-step h3 { font-size: 17px; color: var(--primary-dark); }
.flow-step p { margin-top: 6px; font-size: 13px; color: var(--text-light); }
.flow-arrow { align-self: center; color: var(--accent); font-size: 22px; font-weight: 800; margin-right: 14px; }

/* ---- 五大核心技术 ---- */
.tech-list { display: flex; flex-direction: column; gap: 22px; padding: 26px 0 56px; }
.tech-item {
    display: flex; gap: 22px; align-items: flex-start;
    background: var(--white); border-radius: var(--radius-lg);
    box-shadow: var(--shadow); padding: 26px 28px;
    transition: transform .3s, box-shadow .3s;
}
.tech-item:hover { transform: translateY(-4px); box-shadow: var(--shadow-hover); }
.tech-no {
    flex: none; width: 58px; height: 58px; border-radius: 16px;
    background: linear-gradient(135deg, var(--primary) 0%, #2d8fb0 100%);
    color: #fff; font-size: 22px; font-weight: 800;
    display: flex; align-items: center; justify-content: center;
}
.tech-item:nth-child(even) .tech-no { background: linear-gradient(135deg, var(--accent) 0%, #f0b083 100%); }
.tech-body h2 { font-size: 21px; color: var(--primary-dark); }
.tech-body p { margin-top: 6px; font-size: 14.5px; color: var(--text-body); }

/* ---- 四大训练理念 ---- */
.idea-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 24px; padding: 26px 0 20px; }
.idea-card {
    background: var(--white); border-radius: var(--radius-lg);
    box-shadow: var(--shadow); padding: 28px 26px;
    border-top: 6px solid var(--ic, var(--primary));
    transition: transform .3s, box-shadow .3s;
}
.idea-card:hover { transform: translateY(-4px); box-shadow: var(--shadow-hover); }
.idea-card h2 { font-size: 22px; color: var(--ic, var(--primary-dark)); }
.idea-card p { margin-top: 10px; font-size: 14.5px; color: var(--text-body); }
.i1 { --ic: #2e7fa8; } .i2 { --ic: #55a868; } .i3 { --ic: #dd8452; } .i4 { --ic: #8172b3; }

/* ---- SAAS 云端管控 ---- */
.saas-band {
    margin: 30px 0 56px; border-radius: var(--radius-lg); overflow: hidden;
    background: linear-gradient(150deg, #123a4e 0%, #1a5f7a 55%, #2d8fb0 100%);
    color: #fff; padding: 40px 34px;
}
.saas-band .eyebrow { font-size: 13px; letter-spacing: 3px; color: #ffd9ae; font-weight: 700; }
.saas-band h2 { font-size: 26px; margin-top: 8px; }
.saas-band .saas-sub { margin-top: 8px; color: rgba(255,255,255,.82); font-size: 14.5px; max-width: 720px; }
.saas-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; margin-top: 26px; }
.saas-cell {
    background: rgba(255,255,255,.1); border: 1px solid rgba(255,255,255,.2);
    border-radius: var(--radius); padding: 20px 18px;
}
.saas-cell .sc-icon { font-size: 26px; }
.saas-cell h3 { margin-top: 8px; font-size: 17px; color: #ffe9d2; }
.saas-cell p { margin-top: 6px; font-size: 13.5px; color: rgba(255,255,255,.82); }

/* ---- FIR 引擎条 ---- */
.fir-band {
    margin: 26px 0 56px; background: var(--white); border-radius: var(--radius-lg);
    box-shadow: var(--shadow); padding: 32px 30px;
    display: flex; gap: 26px; align-items: center; flex-wrap: wrap;
}
.fir-band .fir-icon {
    flex: none; width: 72px; height: 72px; border-radius: 20px;
    background: linear-gradient(135deg, var(--accent), #f0b083);
    display: flex; align-items: center; justify-content: center; font-size: 34px;
}
.fir-band h2 { font-size: 22px; color: var(--primary-dark); }
.fir-band p { margin-top: 6px; font-size: 14.5px; color: var(--text-body); max-width: 780px; }

/* ---- 口号条 ---- */
.motto {
    margin: 10px 0 56px; text-align: center;
    background: linear-gradient(135deg, #fff6ec 0%, #fde8d2 100%);
    border: 1px solid rgba(232,144,63,.3);
    border-radius: var(--radius-lg); padding: 34px 26px;
}
.motto p { font-size: 21px; font-weight: 800; color: #a95f16; letter-spacing: 1px; }
.motto small { display: block; margin-top: 8px; font-size: 13.5px; color: var(--text-body); }

/* ---- 页脚 ---- */
.sj-footer {
    background: #123a4e; color: rgba(255,255,255,.75);
    padding: 30px 0; font-size: 14px;
}
.sj-footer .f-inner { display: flex; justify-content: space-between; align-items: center; gap: 18px; flex-wrap: wrap; }
.sj-footer .f-brand { font-size: 17px; font-weight: 800; color: #fff; margin-bottom: 4px; }
.sj-footer a { color: rgba(255,255,255,.85); }
.sj-footer a:hover { color: #ffd9ae; }

/* ---- 动效 ---- */
.reveal { opacity: 0; transform: translateY(26px); transition: opacity .7s ease, transform .7s ease; }
.reveal.in { opacity: 1; transform: none; }

/* ---- 响应式 ---- */
@media (max-width: 900px) {
    .hero h1 { font-size: 33px; }
    .hero { min-height: 0; }
    .hero-inner { padding: 44px 0 4px; }
    .entry-grid { grid-template-columns: 1fr; padding: 22px 0 34px; }
    .duan-grid { grid-template-columns: 1fr; }
    .idea-grid { grid-template-columns: 1fr; }
    .saas-grid { grid-template-columns: 1fr; }
    .tech-item { flex-direction: column; gap: 14px; }
    .flow-arrow { display: none; }
    .flow-step { min-width: 46%; }
    .page-head h1 { font-size: 28px; }
    .sj-links {
        display: none; position: absolute; top: 62px; left: 0; right: 0;
        flex-direction: column; align-items: stretch; gap: 0;
        background: var(--white); border-bottom: 1px solid rgba(34,35,46,.1);
        padding: 8px 14px 14px; box-shadow: var(--shadow);
    }
    .sj-links a { padding: 12px 14px; border-radius: 10px; }
    .sj-links.mobile-open { display: flex; }
    .sj-toggle { display: block; }
}

/* ---- 小屏手机（≤480px）精细适配 ---- */
@media (max-width: 480px) {
    .container { padding: 0 16px; }

    /* 导航 */
    .sj-logo { font-size: 16.5px; gap: 8px; }
    .sj-logo img { width: 32px; height: 32px; }
    .sj-logo small { display: none; }

    /* Hero */
    .hero-inner { padding: 36px 0 2px; }
    .hero .badge { font-size: 12.5px; padding: 5px 13px; }
    .hero h1 { font-size: 26px; letter-spacing: 0; }
    .hero .slogan { font-size: 14.5px; margin-top: 12px; }
    .hero-feats { gap: 8px; margin-top: 16px; }
    .hero-feats span { font-size: 12px; padding: 5px 12px; }
    .hero-quote { padding: 16px 0 24px; }
    .hero-quote p { font-size: 15.5px; }
    .hero-quote small { font-size: 12px; }

    /* 入口卡 */
    .entry-grid { gap: 18px; padding: 18px 0 28px; }
    .ec-body { padding: 20px 18px 18px; }
    .ec-body h2 { font-size: 19px; }

    /* 数据条：两列 */
    .stats-strip { gap: 10px; padding: 24px 0 4px; }
    .stats-strip .stat { flex: 1 1 44%; min-width: 0; padding: 12px 16px; }
    .stats-strip .stat b { font-size: 21px; }
    .stats-strip .stat span { font-size: 12px; }

    /* 页面头 */
    .page-head { padding: 26px 0 6px; }
    .page-head h1 { font-size: 24px; }
    .page-head p.sub { font-size: 14px; }

    /* 四端卡片 */
    .duan-grid { gap: 18px; padding: 20px 0 12px; }
    .duan-card { padding: 22px 18px; }
    .duan-card h2 { font-size: 19px; }
    .duan-card li { font-size: 14px; }

    /* 流程：单列 */
    .flow-wrap { padding: 22px 0 40px; }
    .flow-wrap h2.sec-title { font-size: 21px; }
    .flow-step { min-width: 100%; margin-right: 0; padding: 16px 16px 14px; }

    /* 核心技术 */
    .tech-list { gap: 16px; padding: 20px 0 40px; }
    .tech-item { padding: 20px 18px; gap: 12px; }
    .tech-no { width: 46px; height: 46px; border-radius: 13px; font-size: 18px; }
    .tech-body h2 { font-size: 18px; }
    .tech-body p { font-size: 13.5px; }

    /* 训练理念 */
    .idea-grid { gap: 16px; padding: 20px 0 12px; }
    .idea-card { padding: 22px 18px; }
    .idea-card h2 { font-size: 18px; }
    .idea-card p { font-size: 13.5px; }

    /* FIR 引擎条 */
    .fir-band { padding: 22px 18px; gap: 16px; margin: 20px 0 40px; }
    .fir-band .fir-icon { width: 56px; height: 56px; border-radius: 16px; font-size: 26px; }
    .fir-band h2 { font-size: 18px; }
    .fir-band p { font-size: 13.5px; }

    /* SAAS 云端管控 */
    .saas-band { padding: 26px 18px; margin: 22px 0 40px; }
    .saas-band h2 { font-size: 20px; }
    .saas-band .saas-sub { font-size: 13.5px; }
    .saas-grid { gap: 12px; margin-top: 18px; }
    .saas-cell { padding: 16px 14px; }

    /* 口号条 */
    .motto { padding: 24px 16px; margin: 6px 0 40px; }
    .motto p { font-size: 16px; }
    .motto small { font-size: 12px; }

    /* 页脚 */
    .sj-footer { padding: 24px 0; font-size: 13px; }
    .sj-footer .f-inner { flex-direction: column; align-items: flex-start; gap: 12px; }
}