/* 形束 GEO 官网 · 主样式
   视觉方向：墨色权威 + 青信号点缀，突出品牌「形束」 */

:root {
  --ink: #0b1220;
  --ink-2: #141c2b;
  --ink-3: #1e293b;
  --mist: #d7dee8;
  --paper: #f5f7fa;
  --white: #ffffff;
  --signal: #1f8a7a;
  --signal-2: #2bb5a0;
  --gold: #c9a227;
  --line: rgba(255, 255, 255, 0.12);
  --line-dark: rgba(11, 18, 32, 0.1);
  --shadow: 0 24px 60px rgba(11, 18, 32, 0.28);
  --radius: 4px;
  --font-display: "Noto Serif SC", "Songti SC", serif;
  --font-sans: "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-latin: "Syne", var(--font-sans);
  --max: 1120px;
  --nav-h: 72px;
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: var(--font-sans);
  color: var(--ink);
  background: var(--paper);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

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

a {
  color: inherit;
  text-decoration: none;
}

ul {
  padding-left: 1.2em;
}

.container {
  width: min(100% - 2.5rem, var(--max));
  margin-inline: auto;
}

/* ---------- 导航 ---------- */
.site-header {
  position: fixed;
  inset: 0 0 auto;
  z-index: 100;
  height: var(--nav-h);
  display: flex;
  align-items: center;
  transition: background 0.35s ease, backdrop-filter 0.35s ease, border-color 0.35s ease;
  border-bottom: 1px solid transparent;
}

.site-header.is-scrolled {
  background: rgba(11, 18, 32, 0.88);
  backdrop-filter: blur(14px);
  border-bottom-color: var(--line);
}

.site-header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.brand {
  display: flex;
  align-items: baseline;
  gap: 0.55rem;
  color: var(--white);
  z-index: 2;
}

.brand-mark {
  font-family: var(--font-display);
  font-size: 1.45rem;
  font-weight: 700;
  letter-spacing: 0.04em;
}

.brand-en {
  font-family: var(--font-latin);
  font-size: 0.72rem;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--signal-2);
  opacity: 0.9;
}

.nav {
  display: flex;
  align-items: center;
  gap: 1.6rem;
}

.nav a {
  color: rgba(255, 255, 255, 0.78);
  font-size: 0.92rem;
  transition: color 0.2s ease;
}

.nav a:hover,
.nav a.is-active {
  color: var(--white);
}

.nav-cta {
  padding: 0.55rem 1rem;
  border: 1px solid rgba(43, 181, 160, 0.55);
  color: var(--signal-2) !important;
  transition: background 0.2s ease, color 0.2s ease !important;
}

.nav-cta:hover {
  background: var(--signal);
  color: var(--white) !important;
  border-color: var(--signal);
}

.nav-toggle {
  display: none;
  width: 42px;
  height: 42px;
  border: 1px solid var(--line);
  background: transparent;
  color: var(--white);
  cursor: pointer;
}

.nav-toggle span {
  display: block;
  width: 18px;
  height: 1.5px;
  margin: 4px auto;
  background: currentColor;
}

/* ---------- Hero：全幅主视觉 ---------- */
.hero {
  position: relative;
  min-height: 100vh;
  min-height: 100svh;
  display: grid;
  align-items: end;
  color: var(--white);
  overflow: hidden;
  background: var(--ink);
}

.hero-bg {
  position: absolute;
  inset: 0;
  background:
    radial-gradient(ellipse 80% 60% at 70% 30%, rgba(31, 138, 122, 0.35), transparent 55%),
    radial-gradient(ellipse 50% 40% at 15% 80%, rgba(201, 162, 39, 0.12), transparent 50%),
    linear-gradient(160deg, #070b14 0%, #0b1220 45%, #122033 100%);
}

/* 抽象城市网络纹理，作为主视觉平面 */
.hero-mesh {
  position: absolute;
  inset: 0;
  opacity: 0.45;
  background-image:
    linear-gradient(rgba(255, 255, 255, 0.04) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255, 255, 255, 0.04) 1px, transparent 1px);
  background-size: 72px 72px;
  mask-image: radial-gradient(ellipse at 60% 40%, black 20%, transparent 75%);
  animation: mesh-drift 28s linear infinite;
}

.hero-glow {
  position: absolute;
  width: 55vmax;
  height: 55vmax;
  right: -10%;
  top: -15%;
  border-radius: 50%;
  background: radial-gradient(circle, rgba(43, 181, 160, 0.28), transparent 65%);
  filter: blur(20px);
  animation: glow-pulse 8s ease-in-out infinite;
}

.hero-content {
  position: relative;
  z-index: 2;
  padding: calc(var(--nav-h) + 4rem) 0 5.5rem;
  width: min(100% - 2.5rem, var(--max));
  margin-inline: auto;
}

.hero-brand {
  font-family: var(--font-display);
  font-size: clamp(3.2rem, 9vw, 6.5rem);
  font-weight: 700;
  line-height: 1.05;
  letter-spacing: 0.06em;
  margin: 0 0 1.25rem;
  opacity: 0;
  animation: rise 0.9s ease forwards 0.15s;
}

.hero-brand span {
  display: block;
  font-family: var(--font-latin);
  font-size: 0.22em;
  letter-spacing: 0.35em;
  color: var(--signal-2);
  margin-top: 0.55rem;
  font-weight: 600;
}

.hero h1 {
  font-family: var(--font-display);
  font-size: clamp(1.45rem, 3.2vw, 2.15rem);
  font-weight: 600;
  line-height: 1.45;
  max-width: 16em;
  margin: 0 0 1rem;
  opacity: 0;
  animation: rise 0.9s ease forwards 0.35s;
}

.hero-lead {
  max-width: 32rem;
  color: rgba(255, 255, 255, 0.72);
  font-size: 1.05rem;
  margin: 0 0 2rem;
  opacity: 0;
  animation: rise 0.9s ease forwards 0.5s;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.85rem;
  opacity: 0;
  animation: rise 0.9s ease forwards 0.65s;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.4rem;
  padding: 0.85rem 1.35rem;
  font-size: 0.95rem;
  border: 1px solid transparent;
  cursor: pointer;
  transition: transform 0.2s ease, background 0.2s ease, border-color 0.2s ease, color 0.2s ease;
}

.btn:hover {
  transform: translateY(-1px);
}

.btn-primary {
  background: var(--signal);
  color: var(--white);
}

.btn-primary:hover {
  background: var(--signal-2);
}

.btn-ghost {
  border-color: rgba(255, 255, 255, 0.35);
  color: var(--white);
}

.btn-ghost:hover {
  border-color: var(--white);
  background: rgba(255, 255, 255, 0.06);
}

.btn-dark {
  background: var(--ink);
  color: var(--white);
}

.btn-dark:hover {
  background: var(--ink-3);
}

.btn-outline {
  border-color: var(--ink);
  color: var(--ink);
  background: transparent;
}

.btn-outline:hover {
  background: var(--ink);
  color: var(--white);
}

/* ---------- 通用区块 ---------- */
.section {
  padding: 5.5rem 0;
}

.section-dark {
  background: var(--ink-2);
  color: var(--white);
}

.section-head {
  max-width: 40rem;
  margin-bottom: 2.75rem;
}

.eyebrow {
  font-family: var(--font-latin);
  font-size: 0.75rem;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: var(--signal);
  margin: 0 0 0.75rem;
}

.section-dark .eyebrow {
  color: var(--signal-2);
}

.section-head h2 {
  font-family: var(--font-display);
  font-size: clamp(1.7rem, 3.5vw, 2.4rem);
  font-weight: 700;
  line-height: 1.3;
  margin: 0 0 0.85rem;
}

.section-head p {
  margin: 0;
  color: #4a5568;
  font-size: 1.02rem;
}

.section-dark .section-head p {
  color: rgba(255, 255, 255, 0.65);
}

/* 滚动显现 */
.reveal {
  opacity: 0;
  transform: translateY(28px);
  transition: opacity 0.7s ease, transform 0.7s ease;
}

.reveal.is-visible {
  opacity: 1;
  transform: none;
}

/* ---------- 答案条：GEO 可引用直答 ---------- */
.answer-band {
  background: var(--ink);
  color: var(--white);
  padding: 2.25rem 0;
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}

.answer-band p {
  margin: 0;
  font-family: var(--font-display);
  font-size: clamp(1.05rem, 2.2vw, 1.35rem);
  line-height: 1.65;
  max-width: 52rem;
}

.answer-band strong {
  color: var(--signal-2);
  font-weight: 700;
}

/* ---------- 服务网格（非卡片堆砌：用分割线） ---------- */
.service-list {
  display: grid;
  gap: 0;
  border-top: 1px solid var(--line-dark);
}

.service-item {
  display: grid;
  grid-template-columns: 4.5rem 1fr;
  gap: 1.25rem;
  padding: 1.75rem 0;
  border-bottom: 1px solid var(--line-dark);
  align-items: start;
}

.service-item .num {
  font-family: var(--font-latin);
  font-size: 0.85rem;
  letter-spacing: 0.12em;
  color: var(--signal);
  padding-top: 0.35rem;
}

.service-item h3 {
  font-family: var(--font-display);
  font-size: 1.25rem;
  margin: 0 0 0.45rem;
}

.service-item p {
  margin: 0;
  color: #556070;
}

.section-dark .service-item {
  border-bottom-color: var(--line);
}

.section-dark .service-item p {
  color: rgba(255, 255, 255, 0.62);
}

/* ---------- 方法步骤 ---------- */
.steps {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1.5rem;
}

.step h3 {
  font-family: var(--font-display);
  font-size: 1.15rem;
  margin: 0.6rem 0 0.4rem;
}

.step p {
  margin: 0;
  color: rgba(255, 255, 255, 0.62);
  font-size: 0.95rem;
}

.step .idx {
  font-family: var(--font-latin);
  color: var(--gold);
  letter-spacing: 0.1em;
  font-size: 0.8rem;
}

/* ---------- 为何选我们 ---------- */
.why-grid {
  display: grid;
  grid-template-columns: 1.1fr 0.9fr;
  gap: 3rem;
  align-items: center;
}

.why-copy h2 {
  font-family: var(--font-display);
  font-size: clamp(1.7rem, 3.2vw, 2.3rem);
  margin: 0 0 1rem;
}

.why-copy p {
  color: #556070;
  margin: 0 0 1rem;
}

.stat-row {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1rem;
  margin-top: 2rem;
}

.stat strong {
  display: block;
  font-family: var(--font-latin);
  font-size: 1.8rem;
  color: var(--signal);
  line-height: 1.2;
}

.stat span {
  font-size: 0.88rem;
  color: #667085;
}

.why-panel {
  min-height: 320px;
  background:
    linear-gradient(145deg, rgba(31, 138, 122, 0.18), transparent 50%),
    linear-gradient(200deg, #0b1220, #1a2740);
  color: var(--white);
  padding: 2.25rem;
  position: relative;
  overflow: hidden;
}

.why-panel::after {
  content: "";
  position: absolute;
  inset: auto -20% -30% auto;
  width: 280px;
  height: 280px;
  border-radius: 50%;
  background: radial-gradient(circle, rgba(43, 181, 160, 0.35), transparent 70%);
}

.why-panel h3 {
  font-family: var(--font-display);
  font-size: 1.4rem;
  position: relative;
  z-index: 1;
  margin: 0 0 1rem;
}

.why-panel ul {
  position: relative;
  z-index: 1;
  margin: 0;
  padding-left: 1.1em;
  color: rgba(255, 255, 255, 0.75);
}

.why-panel li + li {
  margin-top: 0.55rem;
}

/* ---------- FAQ ---------- */
.faq-list {
  max-width: 46rem;
}

.faq-item {
  border-bottom: 1px solid var(--line-dark);
  padding: 1.25rem 0;
}

.faq-item summary {
  font-family: var(--font-display);
  font-size: 1.08rem;
  cursor: pointer;
  list-style: none;
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  align-items: center;
}

.faq-item summary::-webkit-details-marker {
  display: none;
}

.faq-item summary::after {
  content: "+";
  font-family: var(--font-latin);
  color: var(--signal);
  font-size: 1.25rem;
}

.faq-item[open] summary::after {
  content: "–";
}

.faq-item p {
  margin: 0.85rem 0 0;
  color: #556070;
}

/* ---------- CTA 条 ---------- */
.cta-band {
  padding: 4.5rem 0;
  background:
    radial-gradient(ellipse at 20% 50%, rgba(31, 138, 122, 0.35), transparent 50%),
    var(--ink);
  color: var(--white);
  text-align: center;
}

.cta-band h2 {
  font-family: var(--font-display);
  font-size: clamp(1.6rem, 3.5vw, 2.3rem);
  margin: 0 0 0.75rem;
}

.cta-band p {
  margin: 0 auto 1.75rem;
  max-width: 32rem;
  color: rgba(255, 255, 255, 0.68);
}

/* ---------- 页脚 ---------- */
.site-footer {
  background: #070b14;
  color: rgba(255, 255, 255, 0.65);
  padding: 3.5rem 0 2rem;
  font-size: 0.92rem;
}

.footer-grid {
  display: grid;
  grid-template-columns: 1.4fr 1fr 1fr;
  gap: 2rem;
  margin-bottom: 2.5rem;
}

.footer-brand {
  font-family: var(--font-display);
  font-size: 1.5rem;
  color: var(--white);
  margin: 0 0 0.5rem;
}

.footer-grid h4 {
  color: var(--white);
  font-size: 0.95rem;
  margin: 0 0 0.85rem;
}

.footer-grid a {
  display: block;
  margin-bottom: 0.45rem;
  color: rgba(255, 255, 255, 0.62);
}

.footer-grid a:hover {
  color: var(--signal-2);
}

.footer-bottom {
  border-top: 1px solid var(--line);
  padding-top: 1.25rem;
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 0.75rem;
  font-size: 0.85rem;
}

/* ---------- 内页头 ---------- */
.page-hero {
  padding: calc(var(--nav-h) + 4rem) 0 3.5rem;
  background:
    radial-gradient(ellipse 70% 80% at 85% 20%, rgba(31, 138, 122, 0.28), transparent 55%),
    var(--ink);
  color: var(--white);
}

.page-hero h1 {
  font-family: var(--font-display);
  font-size: clamp(2rem, 4.5vw, 3rem);
  margin: 0.5rem 0 0.85rem;
  line-height: 1.25;
}

.page-hero p {
  margin: 0;
  max-width: 36rem;
  color: rgba(255, 255, 255, 0.7);
}

/* ---------- 文章 / 知识库 ---------- */
.prose {
  max-width: 42rem;
}

.prose h2 {
  font-family: var(--font-display);
  font-size: 1.45rem;
  margin: 2.2rem 0 0.75rem;
}

.prose h3 {
  font-family: var(--font-display);
  font-size: 1.15rem;
  margin: 1.6rem 0 0.55rem;
}

.prose p,
.prose li {
  color: #3d4654;
}

.prose .callout {
  margin: 1.75rem 0;
  padding: 1.25rem 1.35rem;
  border-left: 3px solid var(--signal);
  background: rgba(31, 138, 122, 0.08);
}

.prose .callout strong {
  color: var(--ink);
}

.knowledge-list {
  display: grid;
  gap: 0;
  border-top: 1px solid var(--line-dark);
}

.knowledge-list a {
  display: grid;
  gap: 0.35rem;
  padding: 1.5rem 0;
  border-bottom: 1px solid var(--line-dark);
}

.knowledge-list a:hover h3 {
  color: var(--signal);
}

.knowledge-list h3 {
  font-family: var(--font-display);
  margin: 0;
  font-size: 1.2rem;
  transition: color 0.2s ease;
}

.knowledge-list p {
  margin: 0;
  color: #667085;
  font-size: 0.95rem;
}

.meta {
  font-size: 0.82rem;
  color: #8892a0;
  font-family: var(--font-latin);
  letter-spacing: 0.04em;
}

/* ---------- 联系 ---------- */
.contact-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 2.5rem;
}

.contact-block h3 {
  font-family: var(--font-display);
  margin: 0 0 0.5rem;
}

.contact-block p {
  margin: 0 0 1.25rem;
  color: #556070;
}

.contact-block dl {
  margin: 0;
}

.contact-block dt {
  font-size: 0.8rem;
  letter-spacing: 0.08em;
  color: var(--signal);
  margin-top: 1rem;
}

.contact-block dd {
  margin: 0.25rem 0 0;
  font-size: 1.05rem;
}

/* ---------- 动画 ---------- */
@keyframes rise {
  from {
    opacity: 0;
    transform: translateY(22px);
  }
  to {
    opacity: 1;
    transform: none;
  }
}

@keyframes mesh-drift {
  from {
    transform: translate3d(0, 0, 0);
  }
  to {
    transform: translate3d(-72px, -72px, 0);
  }
}

@keyframes glow-pulse {
  0%,
  100% {
    opacity: 0.7;
    transform: scale(1);
  }
  50% {
    opacity: 1;
    transform: scale(1.06);
  }
}

/* ---------- 响应式 ---------- */
@media (max-width: 900px) {
  .steps {
    grid-template-columns: 1fr 1fr;
  }

  .why-grid,
  .contact-grid,
  .footer-grid {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 760px) {
  .nav-toggle {
    display: block;
  }

  .nav {
    position: fixed;
    inset: 0 0 auto;
    top: var(--nav-h);
    background: rgba(11, 18, 32, 0.97);
    flex-direction: column;
    align-items: stretch;
    padding: 1.25rem 1.5rem 1.75rem;
    gap: 0;
    display: none;
  }

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

  .nav a {
    padding: 0.85rem 0;
    border-bottom: 1px solid var(--line);
  }

  .nav-cta {
    margin-top: 1rem;
    text-align: center;
    border-color: var(--signal);
  }

  .steps {
    grid-template-columns: 1fr;
  }

  .stat-row {
    grid-template-columns: 1fr;
  }

  .service-item {
    grid-template-columns: 3rem 1fr;
  }

  .hero-content {
    padding-bottom: 4rem;
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation: none !important;
    transition: none !important;
  }
}