/* 一书一AI 宣传站 — 知性青蓝 + 暖金 + 灰白（参考 login_v1.0） */
:root {
  --blue: #177aa5;
  --blue-dark: #125f82;
  --blue-light: #e8f4fa;
  --gold: #f67735;
  --gold-hover: #f77e3e;
  --gold-glow: #feebcb;
  --bg: #f6f7fa;
  --bg-card: #ffffff;
  --ink: #181717;
  --text: #303133;
  --muted: #8e8e93;
  --border: #e4e7ed;
  --radius: 12px;
  --shadow: 0 4px 24px rgba(23, 122, 165, 0.08);
  --header-h: 64px;
  --max-w: 1200px;
  --font: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", system-ui, sans-serif;
}

*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: var(--font);
  color: var(--text);
  background: var(--bg);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}
a { color: var(--blue); text-decoration: none; }
a:hover { color: var(--blue-dark); }
img { max-width: 100%; height: auto; display: block; }
ul { list-style: none; margin: 0; padding: 0; }

.container { width: min(100% - 2rem, var(--max-w)); margin-inline: auto; }

/* Header */
#site-header {
  position: sticky;
  top: 0;
  z-index: 1000;
}
.site-header {
  position: relative;
  z-index: 1002;
  height: var(--header-h);
  background: rgba(255,255,255,.92);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}
.header-inner {
  display: flex; align-items: center; justify-content: space-between;
  height: 100%; gap: 1rem;
}
.logo {
  display: flex; align-items: center; gap: .6rem;
  font-weight: 600; font-size: 1.05rem; color: var(--ink);
}
.logo-mark {
  width: 36px; height: 36px; border-radius: 10px;
  background: linear-gradient(135deg, var(--blue), var(--blue-dark));
  display: grid; place-items: center; color: #fff; font-size: .75rem; font-weight: 700;
}
.nav-desktop { display: flex; align-items: center; gap: 1.5rem; }
.nav-desktop a {
  color: var(--text); font-size: .925rem; transition: color .2s;
}
.nav-desktop a:hover, .nav-desktop a.active { color: var(--blue); }
.header-actions { display: flex; align-items: center; gap: .75rem; }
.lang-toggle {
  border: 1px solid var(--border); background: #fff; border-radius: 8px;
  padding: .35rem .65rem; font-size: .8rem; cursor: pointer; color: var(--text);
}
.lang-toggle:hover { border-color: var(--blue); color: var(--blue); }
.menu-btn {
  display: none; border: none; background: none; cursor: pointer; padding: .5rem;
}
.nav-mobile {
  display: none;
  position: fixed;
  top: var(--header-h);
  left: 0;
  right: 0;
  bottom: 0;
  z-index: 1001;
  background: #fff;
  padding: 1rem;
  flex-direction: column;
  gap: .5rem;
  border-top: 1px solid var(--border);
  overflow-y: auto;
  -webkit-overflow-scrolling: touch;
}
.nav-mobile.open { display: flex; }
body.nav-open { overflow: hidden; }
.nav-mobile a {
  padding: .85rem 1rem; border-radius: var(--radius); color: var(--text);
  background: var(--bg);
}
.nav-mobile a.active { background: var(--blue-light); color: var(--blue); }

/* Buttons */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: .4rem;
  padding: .65rem 1.25rem; border-radius: 8px; font-size: .925rem; font-weight: 500;
  border: none; cursor: pointer; transition: transform .15s, box-shadow .2s;
  text-align: center;
}
.btn-primary {
  color: #fff; background: var(--gold);
  box-shadow: 0 0 20px var(--gold-glow);
}
.btn-primary:hover { background: var(--gold-hover); color: #fff; transform: translateY(-1px); }
.btn-outline {
  background: #fff; color: var(--blue); border: 1px solid var(--blue);
}
.btn-outline:hover { background: var(--blue-light); }
.btn-ghost { background: transparent; color: var(--text); border: 1px solid var(--border); }
.btn-lg { padding: .85rem 1.75rem; font-size: 1rem; }

/* Hero */
.hero {
  padding: 3.5rem 0 4rem;
  background: linear-gradient(180deg, #fff 0%, var(--bg) 100%);
  overflow: hidden;
}
.hero-grid {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: center;
  gap: clamp(1rem, 2.5vw, 1.75rem);
}
.hero-grid > .reveal:first-child {
  flex: 1 1 320px;
  min-width: min(100%, 300px);
  max-width: 34rem;
}
.hero-badge {
  display: inline-block; padding: .35rem .85rem; border-radius: 999px;
  background: var(--blue-light); color: var(--blue); font-size: .8rem; margin-bottom: 1rem;
}
.hero h1 {
  font-size: clamp(1.75rem, 4vw, 2.75rem); line-height: 1.25;
  color: var(--ink); margin: 0 0 1rem; font-weight: 600;
}
.hero h1 em { font-style: normal; color: var(--gold); }
.hero-lead { font-size: 1.05rem; color: var(--muted); margin-bottom: 1.75rem; max-width: 32em; }
.hero-cta { display: flex; flex-wrap: wrap; gap: .75rem; margin-bottom: 2rem; }
.hero-stats { display: flex; flex-wrap: wrap; gap: 1.5rem; }
.hero-stat strong { display: block; font-size: 1.35rem; color: var(--blue); }
.hero-stat span { font-size: .8rem; color: var(--muted); }

/* Knowledge graph visual */
.graph-panel {
  position: relative; aspect-ratio: 1; max-height: 420px;
  background: var(--bg-card); border-radius: var(--radius);
  border: 1px solid var(--border); box-shadow: var(--shadow);
  overflow: hidden;
}
.hero .graph-panel {
  flex: 0 0 auto;
  width: clamp(260px, 34vw, 420px);
  max-height: none;
  aspect-ratio: 1;
  margin-left: 0;
  margin-right: 0;
}
.graph-panel--case {
  aspect-ratio: 4 / 3;
  max-height: 280px;
}
.graph-panel canvas { width: 100%; height: 100%; display: block; }
.graph-float-card {
  position: absolute; bottom: 1rem; left: 1rem; right: 1rem;
  padding: .75rem 1rem; background: rgba(255,255,255,.95);
  border-radius: 8px; font-size: .8rem; border: 1px solid var(--border);
}

/* Sections */
.section { padding: 4rem 0; }
.section-alt { background: #fff; }
.section-head { text-align: center; max-width: 640px; margin: 0 auto 2.5rem; }
.section-head--flow { max-width: none; width: 100%; overflow-x: auto; -webkit-overflow-scrolling: touch; scrollbar-width: none; }
.section-head--flow::-webkit-scrollbar { display: none; }
.section-head h2 { font-size: clamp(1.4rem, 3vw, 2rem); color: var(--ink); margin: 0 0 .75rem; }
.section-head p { color: var(--muted); margin: 0; }
.flow-subtitle {
  white-space: nowrap;
  display: inline-block;
  font-size: clamp(0.78rem, 1.5vw, 0.95rem);
  letter-spacing: 0.01em;
}

/* Flow demo */
.flow-steps {
  display: grid; grid-template-columns: repeat(4, 1fr); gap: 1rem;
}
.flow-steps-6 { grid-template-columns: repeat(6, 1fr); }
.flow-steps-7 { grid-template-columns: repeat(7, 1fr); }
@media (max-width: 1100px) {
  .flow-steps-6 { grid-template-columns: repeat(3, 1fr); }
  .flow-steps-7 { grid-template-columns: repeat(3, 1fr); }
}
@media (max-width: 640px) {
  .flow-steps-6 { grid-template-columns: repeat(2, 1fr); }
  .flow-steps-7 { grid-template-columns: repeat(2, 1fr); }
}
.flow-demo { display: flex; flex-direction: column; gap: 1.5rem; }
.flow-step {
  text-align: center; padding: 1.25rem; background: var(--bg-card);
  border-radius: var(--radius); border: 1px solid var(--border);
  transition: border-color .3s, box-shadow .3s;
  cursor: pointer;
}
.flow-step.active { border-color: var(--blue); box-shadow: var(--shadow); }
.flow-step-num {
  width: 32px; height: 32px; margin: 0 auto .75rem; border-radius: 50%;
  background: var(--blue-light); color: var(--blue); font-weight: 600;
  display: grid; place-items: center; font-size: .85rem;
}
.flow-step.active .flow-step-num { background: var(--blue); color: #fff; }
.flow-step h3 { font-size: .95rem; margin: 0 0 .35rem; color: var(--ink); }
.flow-step p { font-size: .8rem; color: var(--muted); margin: 0; }

/* 单行 GIF / 动画演示区 */
.flow-showcase {
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 1.25rem 1.5rem 1.5rem;
  box-shadow: var(--shadow-soft, 0 4px 24px rgba(23, 122, 165, .06));
}
.flow-showcase-track { position: relative; min-height: 220px; }
.flow-slide {
  position: absolute; inset: 0; display: flex; flex-direction: column;
  align-items: center; justify-content: center; gap: 1rem;
  opacity: 0; visibility: hidden; transform: translateY(8px);
  transition: opacity .45s ease, transform .45s ease, visibility .45s;
  pointer-events: none;
}
.flow-slide.active {
  opacity: 1; visibility: visible; transform: translateY(0);
  pointer-events: auto; z-index: 1;
}
.flow-gif-frame {
  position: relative; width: min(100%, 720px); height: 180px;
  border-radius: calc(var(--radius) - 2px); overflow: hidden;
  background: linear-gradient(145deg, #f0f7fb 0%, #e8f4fa 100%);
  border: 1px solid var(--border);
}
.flow-gif-frame.has-gif .flow-anim { display: none; }
.flow-gif {
  position: absolute; inset: 0; width: 100%; height: 100%;
  object-fit: cover; display: none;
}
.flow-gif-frame.has-gif .flow-gif { display: block; }
.flow-anim {
  position: absolute; inset: 0; display: flex; align-items: center;
  justify-content: center;
}
.flow-showcase-caption {
  margin: 0; font-size: .95rem; color: var(--ink); text-align: center;
  max-width: 36rem; line-height: 1.5;
}

/* 上传 */
.flow-anim-upload { flex-direction: column; gap: .75rem; padding: 1rem; }
.flow-mock-bar { display: flex; gap: 6px; align-self: flex-start; }
.flow-mock-bar span { width: 8px; height: 8px; border-radius: 50%; background: #cbd5e1; }
.flow-mock-bar span:nth-child(1) { background: #f87171; }
.flow-mock-bar span:nth-child(2) { background: #fbbf24; }
.flow-mock-bar span:nth-child(3) { background: #4ade80; }
.flow-mock-drop {
  width: 88%; padding: 1.25rem; border: 2px dashed var(--blue);
  border-radius: 8px; text-align: center; background: #fff;
  animation: flow-pulse 2s ease-in-out infinite;
}
.flow-mock-file { font-size: .85rem; color: var(--blue); font-weight: 600; }
.flow-mock-progress { height: 6px; background: #e2e8f0; border-radius: 3px; margin-top: .75rem; overflow: hidden; }
.flow-mock-progress i {
  display: block; height: 100%; width: 35%; background: var(--blue);
  border-radius: 3px; animation: flow-progress 2.4s ease-in-out infinite;
}

/* 章节解析 */
.flow-mock-chapters { list-style: none; margin: 0; padding: 0; width: 70%; }
.flow-mock-chapters li {
  padding: .45rem .75rem; margin-bottom: .4rem; background: #fff;
  border-radius: 6px; font-size: .8rem; color: var(--ink);
  border: 1px solid var(--border); opacity: 0; transform: translateX(-12px);
  animation: flow-chapter-in .6s ease forwards;
}
.flow-mock-chapters li:nth-child(1) { animation-delay: .1s; }
.flow-mock-chapters li:nth-child(2) { animation-delay: .35s; }
.flow-mock-chapters li:nth-child(3) { animation-delay: .6s; }
.flow-mock-chapters li:nth-child(4) { animation-delay: .85s; }

/* 知识图谱 */
.flow-anim-graph {
  display: flex; align-items: center; justify-content: center;
  width: 100%; height: 100%; padding: 10px; box-sizing: border-box;
}
.flow-mock-graph-svg {
  display: block; width: auto; height: auto;
  max-width: min(100%, 340px); max-height: calc(100% - 8px);
  aspect-ratio: 320 / 180; overflow: visible;
}
.flow-graph-edge {
  fill: none; stroke: rgba(23, 122, 165, .5); stroke-width: 2.5;
  stroke-linecap: round;
  stroke-dasharray: 100; stroke-dashoffset: 100;
  animation: flow-edge-draw 2.2s ease-in-out infinite;
}
.flow-graph-edge:nth-of-type(2) { animation-delay: .15s; }
.flow-graph-edge:nth-of-type(3) { animation-delay: .3s; }
.flow-graph-node {
  fill: #fff; stroke: var(--blue); stroke-width: 2.5;
  transform-box: fill-box; transform-origin: center;
  animation: flow-node-pulse 2s ease-in-out infinite;
}
.flow-graph-node.center {
  fill: var(--blue); stroke: #fff; stroke-width: 2;
  animation: flow-node-pulse-center 2s ease-in-out infinite;
}
.flow-graph-node.n1 { animation-delay: .2s; }
.flow-graph-node.n2 { animation-delay: .4s; }
.flow-graph-node.n3 { animation-delay: .6s; }

/* 思维导图 */
.flow-anim-mindmap { position: relative; width: 100%; height: 100%; }
.flow-mock-mm-root {
  position: absolute; left: 50%; top: 42%; transform: translate(-50%, -50%);
  padding: .35rem .85rem; background: var(--blue); color: #fff;
  border-radius: 6px; font-size: .78rem; font-weight: 600;
}
.flow-mock-mm-branch {
  position: absolute; padding: .3rem .65rem; background: #fff;
  border: 1px solid var(--blue); border-radius: 6px; font-size: .72rem;
  opacity: 0; transform: scale(.6);
  animation: flow-mm-pop .5s ease forwards;
}
.flow-mock-mm-branch.b1 { left: 18%; top: 22%; animation-delay: .25s; }
.flow-mock-mm-branch.b2 { right: 16%; top: 28%; animation-delay: .5s; }
.flow-mock-mm-branch.b3 { left: 42%; bottom: 18%; animation-delay: .75s; }

/* 全书导读 */
.flow-anim-guide { flex-direction: column; gap: .55rem; width: 72%; align-items: stretch; }
.flow-mock-guide-line {
  height: 10px; background: #fff; border-radius: 4px;
  border: 1px solid var(--border); transform-origin: left;
  animation: flow-type-line 2.4s ease-in-out infinite;
}
.flow-mock-guide-line.l1 { width: 92%; animation-delay: 0s; }
.flow-mock-guide-line.l2 { width: 78%; animation-delay: .15s; }
.flow-mock-guide-line.l3 { width: 85%; animation-delay: .3s; }
.flow-mock-guide-line.l4 { width: 60%; animation-delay: .45s; }

/* 抽题 */
.flow-mock-quiz-card {
  width: 78%; padding: 1rem; background: #fff; border-radius: 8px;
  border: 1px solid var(--border); text-align: left;
  animation: flow-quiz-float 2.5s ease-in-out infinite;
}
.flow-mock-quiz-q { margin: 0 0 .65rem; font-size: .82rem; color: var(--ink); }
.flow-mock-quiz-opt {
  display: inline-block; margin-right: .4rem; padding: .25rem .55rem;
  font-size: .72rem; border-radius: 4px; background: #f1f5f9; color: var(--muted);
}
.flow-mock-quiz-opt.active {
  background: var(--blue-light); color: var(--blue); font-weight: 600;
  animation: flow-opt-blink 1.8s ease-in-out infinite;
}

/* 音频 */
.flow-anim-audio { flex-direction: column; gap: .75rem; }
.flow-mock-wave { display: flex; align-items: flex-end; gap: 4px; height: 48px; }
.flow-mock-wave i {
  display: block; width: 5px; background: var(--blue); border-radius: 2px;
  animation: flow-wave 1.1s ease-in-out infinite;
}
.flow-mock-wave i:nth-child(1) { height: 18px; animation-delay: 0s; }
.flow-mock-wave i:nth-child(2) { height: 32px; animation-delay: .08s; }
.flow-mock-wave i:nth-child(3) { height: 24px; animation-delay: .16s; }
.flow-mock-wave i:nth-child(4) { height: 40px; animation-delay: .24s; }
.flow-mock-wave i:nth-child(5) { height: 28px; animation-delay: .32s; }
.flow-mock-wave i:nth-child(6) { height: 36px; animation-delay: .4s; }
.flow-mock-wave i:nth-child(7) { height: 22px; animation-delay: .48s; }
.flow-mock-wave i:nth-child(8) { height: 44px; animation-delay: .56s; }
.flow-mock-wave i:nth-child(9) { height: 26px; animation-delay: .64s; }
.flow-mock-wave i:nth-child(10) { height: 34px; animation-delay: .72s; }
.flow-mock-play {
  width: 36px; height: 36px; border-radius: 50%; background: var(--blue);
  color: #fff; display: grid; place-items: center; font-size: .75rem;
  animation: flow-play-pulse 2s ease-in-out infinite;
}

@keyframes flow-pulse { 0%, 100% { box-shadow: 0 0 0 0 rgba(23, 122, 165, .15); } 50% { box-shadow: 0 0 0 8px rgba(23, 122, 165, 0); } }
@keyframes flow-progress { 0% { width: 8%; } 50% { width: 88%; } 100% { width: 100%; } }
@keyframes flow-chapter-in { to { opacity: 1; transform: translateX(0); } }
@keyframes flow-node-pulse { 0%, 100% { transform: scale(1); box-shadow: 0 0 0 0 rgba(23, 122, 165, .3); } 50% { transform: scale(1.08); box-shadow: 0 0 0 6px rgba(23, 122, 165, 0); } }
@keyframes flow-node-pulse-center { 0%, 100% { transform: scale(1); box-shadow: 0 0 0 0 rgba(255, 255, 255, .4); } 50% { transform: scale(1.08); box-shadow: 0 0 0 6px rgba(255, 255, 255, 0); } }
@keyframes flow-edge-draw { 0% { stroke-dashoffset: 120; } 45%, 100% { stroke-dashoffset: 0; } }
@keyframes flow-mm-pop { to { opacity: 1; transform: scale(1); } }
@keyframes flow-type-line { 0%, 100% { opacity: .35; transform: scaleX(.3); } 50% { opacity: 1; transform: scaleX(1); } }
@keyframes flow-quiz-float { 0%, 100% { transform: translateY(0); } 50% { transform: translateY(-4px); } }
@keyframes flow-opt-blink { 0%, 100% { opacity: 1; } 50% { opacity: .55; } }
@keyframes flow-wave { 0%, 100% { transform: scaleY(.45); } 50% { transform: scaleY(1); } }
@keyframes flow-play-pulse { 0%, 100% { transform: scale(1); } 50% { transform: scale(1.06); } }

@media (max-width: 640px) {
  .flow-gif-frame { height: 160px; }
  .flow-showcase-caption { font-size: .85rem; }
}

/* Feature grid */
.grid-4 { display: grid; grid-template-columns: repeat(4, 1fr); gap: 1.25rem; }
.grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1.25rem; }
.grid-2 { display: grid; grid-template-columns: repeat(2, 1fr); gap: 1.5rem; }
.card {
  background: var(--bg-card); border-radius: var(--radius);
  border: 1px solid var(--border); padding: 1.5rem;
  transition: transform .25s, box-shadow .25s;
}
.card:hover { transform: translateY(-4px); box-shadow: var(--shadow); }
.card-icon {
  width: 48px; height: 48px; border-radius: 12px;
  background: var(--blue-light); color: var(--blue);
  display: grid; place-items: center; font-size: 1.35rem; margin-bottom: 1rem;
}
.card h3 { font-size: 1.05rem; margin: 0 0 .5rem; color: var(--ink); }
.card p { font-size: .875rem; color: var(--muted); margin: 0; }

/* Platform cards */
.platform-card {
  text-align: center; padding: 2rem 1.5rem;
}
.platform-card .card-icon { margin-inline: auto; }
.platform-links { display: flex; flex-wrap: wrap; gap: .5rem; justify-content: center; margin-top: 1rem; }

/* Download page */
.download-cards {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}
.download-card {
  display: flex; gap: 1.5rem; align-items: flex-start;
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 2rem; box-shadow: var(--shadow);
}
.download-card__icon {
  flex-shrink: 0; width: 72px; height: 72px; border-radius: 18px;
  background: linear-gradient(135deg, var(--blue-light), #fff);
  display: grid; place-items: center; font-size: 2rem;
  border: 1px solid var(--border);
}
.download-card__body { flex: 1; min-width: 0; }
.download-card__body h2 { margin: 0 0 .5rem; font-size: 1.5rem; color: var(--ink); }
.download-card__body > p { margin: 0 0 1rem; color: var(--muted); max-width: 52rem; }
.download-meta {
  display: flex; flex-wrap: wrap; gap: 1rem 1.5rem;
  margin: 0 0 1.25rem; padding: 0; list-style: none;
  font-size: .875rem; color: var(--muted);
}
.download-meta strong { color: var(--ink); font-weight: 600; }
.download-btn { margin-bottom: .75rem; }
.download-note { font-size: .8rem; color: var(--muted); margin: 0; max-width: 40rem; }
@media (max-width: 640px) {
  .download-card { flex-direction: column; align-items: stretch; padding: 1.5rem; }
  .download-card__icon { margin-inline: auto; }
}

/* Mindmap preview */
.mindmap-demo {
  font-family: var(--font); text-align: left; padding: 1.5rem;
  background: #fafbfc; border-radius: 8px; border: 1px solid var(--border);
}
.mindmap-root { font-weight: 600; color: var(--blue); margin-bottom: .5rem; }
.mindmap-branch {
  margin-left: 1.25rem; padding-left: .75rem; border-left: 2px solid var(--blue-light);
  overflow: hidden; max-height: 0; opacity: 0; transition: max-height .5s, opacity .4s;
}
.mindmap-branch.open { max-height: 200px; opacity: 1; }
.mindmap-branch li { font-size: .85rem; padding: .2rem 0; color: var(--text); }

/* Case study */
.case-tag {
  display: inline-block; font-size: .75rem; padding: .2rem .6rem;
  border-radius: 4px; background: var(--gold-glow); color: var(--gold); margin-bottom: .75rem;
}

/* FAQ */
.faq-item { border-bottom: 1px solid var(--border); }
.faq-q {
  width: 100%; text-align: left; padding: 1.1rem 0; border: none; background: none;
  font-size: 1rem; font-weight: 500; color: var(--ink); cursor: pointer;
  display: flex; justify-content: space-between; align-items: center; gap: 1rem;
}
.faq-q::after { content: "+"; color: var(--blue); font-size: 1.25rem; }
.faq-item.open .faq-q::after { content: "−"; }
.faq-a {
  max-height: 0; overflow: hidden; transition: max-height .35s;
  font-size: .9rem; color: var(--muted);
}
.faq-item.open .faq-a { max-height: 300px; padding-bottom: 1rem; }

/* Footer */
.site-footer {
  background: var(--ink); color: #ccc; padding: 3rem 0 2rem; margin-top: 2rem;
  overflow: visible;
}
.footer-grid {
  display: grid; grid-template-columns: 2fr 1fr 1fr 1fr; gap: 2rem; margin-bottom: 2rem;
  align-items: start;
  overflow: visible;
}
.site-footer h4 { color: #fff; margin: 0 0 1rem; font-size: .95rem; }
.site-footer a { color: #aaa; font-size: .875rem; display: block; margin-bottom: .5rem; }
.site-footer a:hover { color: var(--gold); }
.footer-wechat {
  margin-top: 12px;
  overflow: visible;
  position: relative;
  z-index: 1;
}
.footer-wechat__label {
  font-size: .8125rem;
  color: #aaa;
  margin-bottom: 8px;
}
.footer-wechat__qr {
  display: block;
  width: 132px;
  height: auto;
  max-width: min(100%, 132px);
  aspect-ratio: 888 / 1131;
  object-fit: contain;
  object-position: top center;
  border-radius: 6px;
  background: #fff;
  padding: 6px;
  box-sizing: border-box;
  position: relative;
  z-index: 2;
  isolation: isolate;
}
.footer-bottom {
  border-top: 1px solid #333; padding-top: 1rem; text-align: center;
  font-size: .8rem; color: #888;
  clear: both;
  position: relative;
  z-index: 0;
}

/* Reveal animation */
.reveal { opacity: 0; transform: translateY(20px); transition: opacity .6s, transform .6s; }
.reveal.visible { opacity: 1; transform: none; }

/* Page hero (inner pages) */
.page-hero {
  padding: 2.5rem 0; background: linear-gradient(135deg, var(--blue-light), #fff);
  border-bottom: 1px solid var(--border);
}
.page-hero h1 { margin: 0 0 .5rem; font-size: clamp(1.5rem, 3vw, 2.25rem); color: var(--ink); }
.page-hero p { margin: 0; color: var(--muted); max-width: 36em; }
.page-hero__row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1.5rem;
}
.page-hero__copy { flex: 1; min-width: 0; }
.page-hero__action { flex-shrink: 0; }
@media (max-width: 720px) {
  .page-hero__row {
    flex-direction: column;
    align-items: flex-start;
  }
}

/* Feature detail blocks */
.feature-block {
  display: grid; grid-template-columns: 1fr 1fr; gap: 2.5rem; align-items: center;
  padding: 2rem 0;
}
.feature-block.reverse { direction: rtl; }
.feature-block.reverse > * { direction: ltr; }
.feature-visual {
  background: var(--bg-card); border-radius: var(--radius);
  border: 1px solid var(--border); min-height: 260px;
  display: flex; align-items: center; justify-content: center; padding: 1.5rem;
  overflow: hidden;
}
.feature-visual--screenshot {
  padding: .75rem;
  background: #f0f2f5;
}
.feature-visual--screenshot img {
  width: 100%;
  height: auto;
  border-radius: 8px;
  box-shadow: var(--shadow);
  object-fit: contain;
}
.feature-list { margin: 1rem 0 0; padding: 0; }
.feature-list li {
  position: relative; padding-left: 1.25rem; margin-bottom: .5rem; font-size: .9rem;
}
.feature-list li::before {
  content: ""; position: absolute; left: 0; top: .55em;
  width: 6px; height: 6px; border-radius: 50%; background: var(--gold);
}

/* Product UI demos (quiz / audio) */
.product-demo { width: 100%; padding: 0; background: transparent; border: none; }
.product-demo-card {
  width: 100%; text-align: left; padding: 1.25rem;
  background: var(--bg); border-radius: 10px; border: 1px solid var(--border);
}
.product-demo-label {
  font-size: .75rem; font-weight: 600; color: var(--blue);
  margin-bottom: .75rem; text-transform: uppercase; letter-spacing: .03em;
}
.product-demo-q { font-size: .95rem; font-weight: 600; color: var(--ink); margin: 0 0 .75rem; line-height: 1.5; }
.product-demo-options { list-style: none; margin: 0; padding: 0; font-size: .85rem; }
.product-demo-options li {
  padding: .45rem .65rem; margin-bottom: .35rem; border-radius: 6px;
  background: #fff; border: 1px solid var(--border); color: var(--muted);
}
.product-demo-options li.selected {
  border-color: var(--blue); background: var(--blue-light); color: var(--ink); font-weight: 500;
}
.product-demo-meta { font-size: .75rem; color: var(--muted); margin: .75rem 0 0; }
.product-demo-script {
  font-size: .85rem; color: var(--muted); line-height: 1.6; margin: 0 0 1rem;
  display: -webkit-box; -webkit-line-clamp: 3; -webkit-box-orient: vertical; overflow: hidden;
}
.audio-controls {
  display: flex; align-items: center; gap: .75rem;
}
.audio-play {
  width: 36px; height: 36px; border-radius: 50%;
  background: var(--blue); color: #fff; font-size: .75rem;
  display: grid; place-items: center; flex-shrink: 0;
}
.audio-wave {
  flex: 1; display: flex; align-items: center; gap: 3px; height: 28px;
}
.audio-wave span {
  flex: 1; max-width: 6px; border-radius: 3px; background: var(--blue);
  animation: audio-bar 1.2s ease-in-out infinite;
}
.audio-wave span:nth-child(2) { animation-delay: .15s; height: 60%; }
.audio-wave span:nth-child(3) { animation-delay: .3s; height: 85%; }
.audio-wave span:nth-child(4) { animation-delay: .45s; height: 50%; }
.audio-wave span:nth-child(5) { animation-delay: .6s; height: 70%; }
.audio-wave span:nth-child(1) { height: 40%; }
@keyframes audio-bar {
  0%, 100% { transform: scaleY(.4); opacity: .5; }
  50% { transform: scaleY(1); opacity: 1; }
}
.audio-time { font-size: .75rem; color: var(--muted); white-space: nowrap; }

/* Interactive book (aiwork-editor) demos */
.ib-editor-demo { padding: 0; overflow: hidden; }
.ib-editor-bar {
  padding: .55rem .9rem; font-size: .75rem; font-weight: 600;
  color: var(--blue); background: var(--blue-light); border-bottom: 1px solid var(--border);
}
.ib-editor-body { padding: 1rem 1.1rem 1.15rem; }
.ib-editor-line { margin: 0 0 .55rem; font-size: .9rem; color: var(--ink); line-height: 1.65; }
.ib-editor-line--ruby { color: var(--text); }
.ib-ruby {
  position: relative; display: inline-block; margin: 0 .05em;
  padding-top: .85em; font-size: 1em;
}
.ib-ruby rt {
  position: absolute; left: 50%; top: 0; transform: translateX(-50%);
  font-size: .55em; color: var(--blue); font-style: normal; white-space: nowrap;
}
.ib-blank {
  display: inline-block; min-width: 7em; margin: .35rem 0 .75rem;
  padding: .35rem .65rem; border-bottom: 2px dashed var(--blue);
  font-size: .8rem; color: var(--muted); background: #fff;
}
.ib-slash {
  display: inline-block; padding: .3rem .65rem; border-radius: 6px;
  background: #fff; border: 1px solid var(--border); font-size: .78rem; color: var(--muted);
}
.ib-teach-demo .ib-teach-line { margin: 0 0 .75rem; font-size: .9rem; color: var(--ink); }
.ib-circled {
  display: inline-flex; align-items: center; justify-content: center;
  width: 1.35em; height: 1.35em; margin-right: .25rem;
  border-radius: 50%; border: 1.5px solid var(--gold); color: var(--gold);
  font-size: .85rem; font-weight: 600; vertical-align: middle;
}
.ib-audio-inline {
  display: flex; align-items: center; gap: .5rem;
  padding: .55rem .75rem; margin-bottom: .5rem;
  background: #fff; border: 1px solid var(--border); border-radius: 8px;
  font-size: .85rem; color: var(--muted);
}
.ib-audio-icon {
  width: 28px; height: 28px; border-radius: 50%;
  background: var(--blue); color: #fff; font-size: .75rem;
  display: grid; place-items: center; flex-shrink: 0;
}
.ib-reader-demo { background: linear-gradient(180deg, #f8fafc, #fff); }
.ib-reader-chrome {
  display: flex; gap: 5px; margin-bottom: .85rem;
}
.ib-reader-chrome span {
  width: 8px; height: 8px; border-radius: 50%; background: #d0d5dd;
}
.ib-reader-title {
  margin: 0 0 .5rem; font-size: 1rem; font-weight: 600; color: var(--ink);
}
.ib-reader-actions {
  display: flex; flex-wrap: wrap; gap: .5rem; margin-top: .75rem;
}
.ib-reader-actions span {
  font-size: .75rem; padding: .3rem .65rem; border-radius: 999px;
  background: var(--blue-light); color: var(--blue); font-weight: 500;
}
.ib-module-grid .card h3 { font-size: .98rem; }
.ib-module-grid .card p { font-size: .82rem; line-height: 1.5; }

/* FutureBook publishing platform */
.db-card-num {
  font-size: .75rem; font-weight: 700; letter-spacing: .08em;
  color: var(--blue); margin-bottom: .5rem;
}
.db-product-grid .card { position: relative; }
.db-product-span { grid-column: 1 / -1; }
.db-arch {
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 1.5rem 1.25rem 1.75rem;
  box-shadow: var(--shadow);
}
.db-arch-title {
  margin: 0 0 .85rem; font-size: .95rem; color: var(--ink);
}
.db-arch-title + .db-arch-row { margin-bottom: 1.5rem; }
.db-arch-row {
  display: grid; grid-template-columns: repeat(3, 1fr); gap: .75rem;
}
.db-arch-row--base { grid-template-columns: repeat(4, 1fr); }
.db-chip {
  background: var(--blue-light); border: 1px solid #cfe6f2;
  border-radius: 10px; padding: .85rem .9rem;
  display: flex; flex-direction: column; gap: .35rem;
}
.db-chip strong { font-size: .9rem; color: var(--ink); }
.db-chip span { font-size: .78rem; color: var(--muted); line-height: 1.45; }
.db-chip--base {
  background: #fff; border-color: var(--border);
}
.db-phone-row {
  display: flex; gap: .75rem; justify-content: center; align-items: flex-end;
  width: 100%;
}
.db-phone {
  margin: 0; flex: 1; max-width: 160px;
  background: #111; border-radius: 18px; padding: 6px;
  box-shadow: var(--shadow); border: 1px solid #222;
}
.db-phone img {
  width: 100%; height: auto; border-radius: 12px; display: block;
}
@media (max-width: 960px) {
  .db-arch-row, .db-arch-row--base { grid-template-columns: repeat(2, 1fr); }
  .db-product-span { grid-column: auto; }
}
@media (max-width: 640px) {
  .db-arch-row, .db-arch-row--base { grid-template-columns: 1fr; }
  .db-phone--hide-sm { display: none; }
  .db-phone { max-width: 180px; }
}

/* CTA band */
.cta-band {
  background: linear-gradient(135deg, var(--blue), var(--blue-dark));
  color: #fff; padding: 3rem 2rem; border-radius: var(--radius);
  text-align: center; margin: 2rem 0;
}
.cta-band h2 { margin: 0 0 .75rem; font-size: 1.5rem; }
.cta-band p { margin: 0 0 1.5rem; opacity: .9; }
.cta-band a { color: #fff; text-decoration: underline; }
.cta-band a:hover { color: #fff; opacity: .9; }
.cta-band .btn-primary { background: var(--gold); }

/* Responsive */
@media (max-width: 960px) {
  .hero-grid {
    flex-direction: column;
    align-items: stretch;
  }
  .hero-grid > .reveal:first-child {
    max-width: none;
  }
  .hero .graph-panel {
    width: min(100%, 420px);
    margin-inline: auto;
  }
  .feature-block, .footer-grid { grid-template-columns: 1fr; }
  .feature-block.reverse { direction: ltr; }
  .grid-4 { grid-template-columns: repeat(2, 1fr); }
  .flow-steps { grid-template-columns: repeat(2, 1fr); }
}
@media (max-width: 640px) {
  .nav-desktop { display: none; }
  .menu-btn { display: block; }
  .grid-4, .grid-3, .grid-2, .flow-steps { grid-template-columns: 1fr; }
  .hero { padding-top: 2rem; }
  .footer-grid { grid-template-columns: 1fr 1fr; }
  .header-actions .btn span.hide-mobile { display: none; }
}