/* ==========================================================================
   B站学霸笔记AI 官网 —— 设计系统
   参照 heylillian.com：Inter + 系统中文黑体、#F7F8FA 背景、#2E6DE9 主蓝、
   #120652 标题深紫蓝、10px 圆角按钮 + 多层柔和投影、滚动渐显。
   ========================================================================== */

@font-face {
  font-family: 'Inter'; font-style: normal; font-weight: 100 900; font-display: swap;
  src: url('../fonts/inter-latin.woff2') format('woff2');
  unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+0304, U+0308, U+0329, U+2000-206F, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;
}
@font-face {
  font-family: 'Inter'; font-style: normal; font-weight: 100 900; font-display: swap;
  src: url('../fonts/inter-latin-ext.woff2') format('woff2');
  unicode-range: U+0100-02BA, U+02BD-02C5, U+02C7-02CC, U+02CE-02D7, U+02DD-02FF, U+0304, U+0308, U+0329, U+1D00-1DBF, U+1E00-1E9F, U+1EF2-1EFF, U+2020, U+20A0-20AB, U+20AD-20C0, U+2113, U+2C60-2C7F, U+A720-A7FF;
}

:root {
  --bg: #F7F8FA;
  --card: #FFFFFF;
  --ink: #120652;          /* 大标题 */
  --text: #111827;
  --muted: #5B6478;
  --line: rgba(17, 24, 39, .09);
  --brand: #2E6DE9;
  --brand-d: #1F57C4;
  --brand-soft: #EAF1FE;
  --pink: #FB7299;         /* B站粉，做点缀 */
  --header-h: 68px;
  --radius: 10px;
  --radius-lg: 20px;
  --shadow-btn: 0 4px 9px rgba(0,0,0,.10), 0 17px 17px rgba(0,0,0,.09), 0 38px 23px rgba(0,0,0,.05), 0 68px 27px rgba(0,0,0,.01);
  --shadow-card: 0 1px 2px rgba(16,24,40,.04), 0 8px 24px rgba(16,24,40,.06);
  --shadow-pop: 0 2px 6px rgba(16,24,40,.06), 0 18px 44px rgba(16,24,40,.12);
}

* { box-sizing: border-box; margin: 0; padding: 0; }
h1, h2, h3, h4, h5, h6 { font-size: inherit; font-weight: inherit; }
a { color: inherit; text-decoration: none; }
ul, ol { list-style: none; }
img, svg { display: block; max-width: 100%; }
button { font: inherit; color: inherit; background: none; border: 0; cursor: pointer; }

html { scroll-behavior: smooth; }
body {
  font-family: Inter, -apple-system, BlinkMacSystemFont, 'Segoe UI', Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji';
  background: var(--bg); color: var(--text);
  -webkit-font-smoothing: antialiased;
  font-variant-numeric: tabular-nums;
  overflow-x: hidden;
  line-height: 1.6;
}

.wrap { width: 100%; max-width: 1200px; margin: 0 auto; padding: 0 24px; }
.center { text-align: center; }

/* ── 顶部导航：吸顶，滚动后加毛玻璃与描边 ───────────────────────────── */
.hdr {
  position: fixed; inset: 0 0 auto 0; z-index: 60; height: var(--header-h);
  display: flex; align-items: center;
  background: rgba(247, 248, 250, 0);
  border-bottom: 1px solid transparent;
  transition: background .3s ease, border-color .3s ease, backdrop-filter .3s ease;
}
.hdr.is-stuck {
  background: rgba(255, 255, 255, .82);
  backdrop-filter: saturate(180%) blur(12px);
  -webkit-backdrop-filter: saturate(180%) blur(12px);
  border-bottom-color: var(--line);
}
.hdr .wrap { display: flex; align-items: center; gap: 28px; }
.brand { display: flex; align-items: center; gap: 9px; font-weight: 700; color: var(--ink); font-size: 16.5px; letter-spacing: -.01em; }
.brand img { width: 30px; height: 30px; border-radius: 8px; }
.nav { display: flex; align-items: center; gap: 26px; margin-left: 6px; }
.nav a { font-size: 15px; color: #3D4657; position: relative; padding: 6px 0; transition: color .2s ease; }
.nav a::after {
  content: ''; position: absolute; left: 0; right: 0; bottom: 0; height: 2px; border-radius: 2px;
  background: var(--brand); transform: scaleX(0); transform-origin: center; transition: transform .26s cubic-bezier(.22,.61,.36,1);
}
.nav a:hover { color: var(--brand); }
.nav a:hover::after, .nav a.active::after { transform: scaleX(1); }
.nav a.active { color: var(--brand); font-weight: 600; }
.hdr-cta { margin-left: auto; display: flex; align-items: center; gap: 12px; }

.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  border-radius: var(--radius); font-weight: 600; white-space: nowrap;
  transition: background-color .2s ease, color .2s ease, box-shadow .25s ease, border-color .2s ease;
}
.btn-sm { height: 40px; padding: 0 20px; font-size: 15px; }
.btn-lg { padding: 14px 30px; font-size: 18px; }
.btn-primary { background: var(--brand); color: #fff; }
.btn-primary:hover { background: var(--brand-d); }
.btn-lg.btn-primary { box-shadow: var(--shadow-btn); }
.btn-ghost { background: #fff; color: var(--ink); border: 1px solid var(--line); }
.btn-ghost:hover { border-color: rgba(46, 109, 233, .45); color: var(--brand); }
.btn-quiet { color: #3D4657; }
.btn-quiet:hover { color: var(--brand); }

.burger { display: none; width: 40px; height: 40px; border-radius: 10px; align-items: center; justify-content: center; }
.burger span { display: block; width: 18px; height: 2px; background: var(--ink); border-radius: 2px; position: relative; }
.burger span::before, .burger span::after { content: ''; position: absolute; left: 0; width: 18px; height: 2px; background: var(--ink); border-radius: 2px; transition: transform .25s ease; }
.burger span::before { top: -6px; }
.burger span::after { top: 6px; }

/* ── 通用区块 ─────────────────────────────────────────────────────── */
main { padding-top: var(--header-h); }
.sec { padding: 92px 0; position: relative; }
.sec-tight { padding: 64px 0; }
.eyebrow {
  display: inline-flex; align-items: center; gap: 7px; height: 30px; padding: 0 13px;
  border-radius: 999px; background: var(--brand-soft); color: var(--brand);
  font-size: 13px; font-weight: 600; letter-spacing: .01em;
}
.eyebrow svg { width: 14px; height: 14px; }
h1, .h1 { font-size: clamp(34px, 5.4vw, 72px); line-height: 1.24; font-weight: 600; color: var(--ink); letter-spacing: -.015em; }
h2, .h2 { font-size: clamp(26px, 3.3vw, 44px); line-height: 1.3; font-weight: 600; color: var(--ink); letter-spacing: -.012em; }
h3, .h3 { font-size: 19px; font-weight: 600; color: var(--ink); line-height: 1.45; }
.lead { font-size: clamp(15px, 1.35vw, 18px); color: var(--muted); line-height: 1.75; }
.sec-head { max-width: 760px; margin: 0 auto 52px; text-align: center; }
.sec-head .lead { margin-top: 16px; }
.sec-head .eyebrow { margin-bottom: 18px; }
.grad-text { background: linear-gradient(96deg, #2E6DE9 0%, #6E8BFF 48%, #FB7299 100%); -webkit-background-clip: text; background-clip: text; color: transparent; }

/* 滚动渐显 —— 与参照站同款：淡入 + 上浮 22px，逐个 40ms 阶梯 */
.rv { opacity: 0; transform: translateY(22px); transition: opacity .7s cubic-bezier(.22,.61,.36,1), transform .7s cubic-bezier(.22,.61,.36,1); }
.rv.in { opacity: 1; transform: none; }
@media (prefers-reduced-motion: reduce) {
  .rv { opacity: 1; transform: none; transition: none; }
  html { scroll-behavior: auto; }
}

/* ── Hero ────────────────────────────────────────────────────────── */
.hero { position: relative; padding: 74px 0 0; overflow: hidden; }
.hero-bg { position: absolute; inset: -180px 0 auto 0; height: 900px; z-index: -1; pointer-events: none; }
.hero-bg::before {
  content: ''; position: absolute; left: 50%; top: 0; width: 1300px; height: 900px; transform: translateX(-50%);
  background:
    radial-gradient(closest-side, rgba(46,109,233,.16), transparent 72%) 22% 30% / 760px 620px no-repeat,
    radial-gradient(closest-side, rgba(251,114,153,.13), transparent 70%) 80% 22% / 620px 560px no-repeat,
    radial-gradient(closest-side, rgba(110,139,255,.14), transparent 72%) 55% 60% / 900px 520px no-repeat;
  filter: blur(6px);
}
.hero-inner { max-width: 900px; margin: 0 auto; text-align: center; }
.hero h1 { margin: 22px 0 0; }
.hero .lead { margin: 22px auto 0; max-width: 720px; }
.hero-cta { display: flex; gap: 14px; justify-content: center; margin-top: 34px; flex-wrap: wrap; }
.hero-note { margin-top: 16px; font-size: 13.5px; color: #7A8395; }
.hero-stage { margin: 54px auto 0; max-width: 1000px; }

/* 浏览器窗口模型（矢量） */
.mock {
  border-radius: 16px; overflow: hidden; background: #fff;
  box-shadow: var(--shadow-pop); border: 1px solid var(--line);
}
.mock-bar { height: 34px; background: #EDEFF3; display: flex; align-items: center; gap: 6px; padding: 0 12px; border-bottom: 1px solid var(--line); }
.mock-bar i { width: 9px; height: 9px; border-radius: 50%; display: block; }
.mock-url { flex: 1; height: 20px; margin-left: 8px; border-radius: 6px; background: #fff; border: 1px solid var(--line); font-size: 11px; color: #8A93A5; display: flex; align-items: center; padding: 0 9px; }
.mock-body { display: flex; min-height: 380px; background: #fff; }
.mock-video { flex: 1 1 auto; padding: 18px; }
.mock-side { flex: 0 0 300px; border-left: 1px solid var(--line); background: #FBFCFE; padding: 16px 14px; display: flex; flex-direction: column; gap: 12px; }

/* 打字机 / 逐条出现（hero 侧栏演示） */
.tw-line { opacity: 0; animation: twIn .5s ease forwards; }
@keyframes twIn { from { opacity: 0; transform: translateY(8px); } to { opacity: 1; transform: none; } }
.pulse-dot { animation: pulseDot 1.5s ease-in-out infinite; }
@keyframes pulseDot { 0%, 100% { opacity: 1; transform: scale(1); } 50% { opacity: .4; transform: scale(.82); } }

/* ── 滚动展示条（marquee） ───────────────────────────────────────── */
.marquee { overflow: hidden; padding: 10px 0; -webkit-mask-image: linear-gradient(to right, transparent, #000 8%, #000 92%, transparent); mask-image: linear-gradient(to right, transparent, #000 8%, #000 92%, transparent); }
.marquee-track { display: flex; gap: 14px; width: max-content; animation: mq 34s linear infinite; }
.marquee:hover .marquee-track { animation-play-state: paused; }
@keyframes mq { from { transform: translateX(0); } to { transform: translateX(-50%); } }
.chip {
  display: inline-flex; align-items: center; gap: 8px; height: 44px; padding: 0 18px;
  border-radius: 999px; background: #fff; border: 1px solid var(--line); color: #3D4657;
  font-size: 14.5px; font-weight: 500; white-space: nowrap; box-shadow: 0 1px 2px rgba(16,24,40,.04);
}
.chip svg { width: 16px; height: 16px; color: var(--brand); }

/* ── 卡片 / 网格 ─────────────────────────────────────────────────── */
.grid { display: grid; gap: 22px; }
.g3 { grid-template-columns: repeat(3, 1fr); }
.g2 { grid-template-columns: repeat(2, 1fr); }
.g4 { grid-template-columns: repeat(4, 1fr); }
.card {
  background: var(--card); border: 1px solid var(--line); border-radius: var(--radius-lg);
  padding: 28px; box-shadow: var(--shadow-card);
  transition: box-shadow .28s ease, border-color .28s ease;
}
/* 卡片不做上浮：只加深阴影与描边 */
.card:hover { box-shadow: var(--shadow-pop); border-color: rgba(46,109,233,.28); }
.card .h3 { margin-bottom: 9px; }
.card p { color: var(--muted); font-size: 15px; }
.card-ico {
  width: 46px; height: 46px; border-radius: 13px; display: grid; place-items: center; margin-bottom: 18px;
  background: var(--brand-soft); color: var(--brand);
}
.card-ico svg { width: 24px; height: 24px; }
.step-no { font-size: 13px; font-weight: 700; color: var(--brand); letter-spacing: .08em; margin-bottom: 12px; }

/* 特性大图文行 */
.feat { display: grid; grid-template-columns: 1fr 1fr; gap: 64px; align-items: center; }
.feat + .feat { margin-top: 108px; }
.feat.rev .feat-txt { order: 2; }
.feat-txt .h2 { margin: 16px 0 18px; }
.feat-list { margin-top: 24px; display: flex; flex-direction: column; gap: 13px; }
.feat-list li { display: flex; gap: 11px; align-items: flex-start; color: #3D4657; font-size: 15.5px; }
.feat-list svg { flex: 0 0 auto; width: 20px; height: 20px; color: var(--brand); margin-top: 2px; }
.feat-art {
  border-radius: var(--radius-lg); background: #fff; border: 1px solid var(--line);
  box-shadow: var(--shadow-card); padding: 24px; overflow: hidden;
}

/* 数字条 */
.stats { display: grid; grid-template-columns: repeat(4, 1fr); gap: 20px; }
.stat { text-align: center; padding: 22px 12px; }
.stat b { display: block; font-size: clamp(28px, 3.4vw, 40px); font-weight: 700; color: var(--ink); line-height: 1.2; }
.stat span { font-size: 14px; color: var(--muted); }

/* ── 价格 ────────────────────────────────────────────────────────── */
.pr-toggle { display: inline-flex; padding: 4px; border-radius: 999px; background: #EDF0F5; margin: 0 auto; }
.pr-toggle button { height: 38px; padding: 0 22px; border-radius: 999px; font-size: 14.5px; font-weight: 600; color: #5B6478; transition: background-color .24s ease, color .24s ease, box-shadow .24s ease; }
.pr-toggle button.on { background: #fff; color: var(--ink); box-shadow: 0 1px 3px rgba(16,24,40,.14); }
.pr-save { color: var(--brand); font-size: 12.5px; font-weight: 700; margin-left: 6px; }
.plans { display: grid; grid-template-columns: repeat(3, 1fr); gap: 22px; align-items: start; margin-top: 44px; }
.plan { background: #fff; border: 1px solid var(--line); border-radius: var(--radius-lg); padding: 32px 28px; box-shadow: var(--shadow-card); position: relative; transition: box-shadow .28s ease, border-color .28s ease; }
.plan:hover { box-shadow: var(--shadow-pop); }
.plan.hot { border-color: rgba(46,109,233,.5); box-shadow: 0 2px 6px rgba(46,109,233,.10), 0 20px 44px rgba(46,109,233,.14); }
.plan-tag { position: absolute; top: -13px; left: 28px; height: 26px; padding: 0 12px; border-radius: 999px; background: var(--brand); color: #fff; font-size: 12.5px; font-weight: 700; display: inline-flex; align-items: center; }
.plan h3 { font-size: 17px; font-weight: 600; color: var(--ink); }
.plan .price { display: flex; align-items: baseline; gap: 8px; margin: 16px 0 4px; }
.plan .price b { font-size: 42px; font-weight: 700; color: var(--ink); letter-spacing: -.02em; line-height: 1; }
.plan .price s { color: #9AA2B1; font-size: 17px; }
.plan .price em { font-style: normal; color: var(--muted); font-size: 14.5px; }
.plan .price-sub { font-size: 13.5px; color: var(--muted); min-height: 20px; }
.plan .btn { width: 100%; margin: 22px 0 24px; }
.plan ul { display: flex; flex-direction: column; gap: 12px; }
.plan li { display: flex; gap: 10px; font-size: 14.5px; color: #3D4657; align-items: flex-start; }
.plan li svg { flex: 0 0 auto; width: 18px; height: 18px; color: var(--brand); margin-top: 3px; }
.plan li.off { color: #9AA2B1; }
.plan li.off svg { color: #C6CCD6; }

/* 对比表 */
.cmp { width: 100%; border-collapse: separate; border-spacing: 0; background: #fff; border: 1px solid var(--line); border-radius: var(--radius-lg); overflow: hidden; box-shadow: var(--shadow-card); }
.cmp th, .cmp td { padding: 16px 20px; text-align: left; font-size: 15px; border-bottom: 1px solid var(--line); }
.cmp thead th { background: #F9FAFC; color: var(--ink); font-weight: 600; font-size: 14.5px; }
.cmp tbody tr:last-child td { border-bottom: 0; }
.cmp td:not(:first-child) { text-align: center; color: var(--muted); }
.cmp .yes { color: var(--brand); }

/* ── FAQ ─────────────────────────────────────────────────────────── */
.faq-tabs { display: flex; gap: 8px; flex-wrap: wrap; justify-content: center; margin-bottom: 34px; }
.faq-tabs button { height: 38px; padding: 0 18px; border-radius: 999px; background: #fff; border: 1px solid var(--line); font-size: 14.5px; font-weight: 500; color: #3D4657; transition: all .22s ease; }
.faq-tabs button.on { background: var(--brand); border-color: var(--brand); color: #fff; }
.faq { max-width: 860px; margin: 0 auto; display: flex; flex-direction: column; gap: 12px; }
.qa { background: #fff; border: 1px solid var(--line); border-radius: 14px; box-shadow: 0 1px 2px rgba(16,24,40,.04); transition: box-shadow .26s ease, border-color .26s ease; }
.qa:hover { border-color: rgba(46,109,233,.28); }
.qa.open { box-shadow: var(--shadow-card); border-color: rgba(46,109,233,.35); }
.qa-q { width: 100%; display: flex; align-items: center; gap: 16px; padding: 20px 22px; text-align: left; font-size: 16.5px; font-weight: 600; color: var(--ink); }
.qa-q span { flex: 1; }
.qa-ico { flex: 0 0 auto; width: 22px; height: 22px; color: var(--brand); transition: transform .3s cubic-bezier(.22,.61,.36,1); }
.qa.open .qa-ico { transform: rotate(45deg); }
.qa-a { display: grid; grid-template-rows: 0fr; transition: grid-template-rows .34s cubic-bezier(.22,.61,.36,1); }
.qa.open .qa-a { grid-template-rows: 1fr; }
.qa-a > div { overflow: hidden; }
.qa-a p { padding: 0 22px 22px; color: var(--muted); font-size: 15.5px; }
.qa-a p + p { padding-top: 0; }

/* ── 终幕 CTA ────────────────────────────────────────────────────── */
.cta-band { position: relative; border-radius: 28px; padding: 66px 40px; text-align: center; overflow: hidden; background: linear-gradient(135deg, #123A8C 0%, #2E6DE9 52%, #5B7DF0 100%); }
.cta-band::after { content: ''; position: absolute; inset: 0; background: radial-gradient(closest-side, rgba(255,255,255,.22), transparent 70%) 18% 12% / 460px 380px no-repeat, radial-gradient(closest-side, rgba(251,114,153,.30), transparent 72%) 86% 82% / 520px 420px no-repeat; pointer-events: none; }
.cta-band .h2, .cta-band p { color: #fff; position: relative; z-index: 1; }
.cta-band p { margin: 16px auto 0; max-width: 560px; opacity: .9; }
.cta-band .btn { position: relative; z-index: 1; margin-top: 30px; background: #fff; color: var(--brand); }
.cta-band .btn:hover { background: #F0F5FF; }

/* ── 页脚 ────────────────────────────────────────────────────────── */
.ftr { background: #fff; border-top: 1px solid var(--line); padding: 62px 0 30px; margin-top: 20px; }
.ftr-top { display: grid; grid-template-columns: 1.6fr 1fr 1fr 1fr; gap: 40px; }
.ftr-top p { color: var(--muted); font-size: 14.5px; margin-top: 16px; max-width: 320px; }
.ftr h4 { font-size: 14px; font-weight: 700; color: var(--ink); margin-bottom: 16px; }
.ftr li + li { margin-top: 11px; }
.ftr li a { font-size: 14.5px; color: var(--muted); transition: color .2s ease; }
.ftr li a:hover { color: var(--brand); }
.ftr-btm { margin-top: 44px; padding-top: 22px; border-top: 1px solid var(--line); display: flex; justify-content: space-between; gap: 16px; flex-wrap: wrap; color: #8A93A5; font-size: 13.5px; }

/* ── 响应式 ──────────────────────────────────────────────────────── */
@media (max-width: 980px) {
  .g3, .g4, .plans { grid-template-columns: 1fr 1fr; }
  .feat { grid-template-columns: 1fr; gap: 34px; }
  .feat.rev .feat-txt { order: 0; }
  .feat + .feat { margin-top: 72px; }
  .ftr-top { grid-template-columns: 1fr 1fr; }
  .mock-side { flex-basis: 250px; }
}
@media (max-width: 760px) {
  .nav, .hdr-cta .btn-quiet { display: none; }
  .burger { display: flex; }
  .hdr.nav-open .nav {
    display: flex; flex-direction: column; gap: 4px; position: fixed; top: var(--header-h); left: 0; right: 0;
    background: #fff; border-bottom: 1px solid var(--line); padding: 12px 24px 18px; box-shadow: var(--shadow-card);
  }
  .hdr.nav-open .nav a { padding: 12px 0; font-size: 16px; }
  .sec { padding: 64px 0; }
  .g3, .g4, .g2, .plans, .stats { grid-template-columns: 1fr; }
  .mock-body { flex-direction: column; min-height: 0; }
  .mock-side { flex-basis: auto; border-left: 0; border-top: 1px solid var(--line); }
  .cta-band { padding: 48px 22px; border-radius: 20px; }
  .ftr-top { grid-template-columns: 1fr; gap: 30px; }
}