/* ============================================================
   CAD 工作台 宣传官网样式 v4（bigmodel.cn 风格参照重排）
   字体：Noto Sans SC / 思源黑体（OFL 开源，可免费商用），零版权风险
   字号收敛：正文 14px / 卡片题 17px / 区题 34px / 主标 48px
   白底 + 黑灰阶五档 + 单主蓝 #2563eb + 蓝紫同系渐变仅点缀
   卡片：无边框软阴影 + 12px 圆角 + 角标 + 底部箭头链接
   零依赖 · 原生动画 · 图标全 SVG · 禁 Emoji
   ============================================================ */

:root {
  --bg: #ffffff;
  --bg-alt: #fafbfc;
  --ink: #181c28;
  --body: #4b5563;
  --muted: #6b7280;
  --faint: #9aa3af;
  --line: #e5e8ee;
  --accent: #2563eb;
  --accent-deep: #1d4ed8;
  --accent-tint: #eef4ff;
  --shadow-sm: 0 1px 2px rgba(24, 28, 40, 0.04);
  --shadow-card: 0 1px 2px rgba(24, 28, 40, 0.03), 0 10px 30px rgba(24, 28, 40, 0.06);
  --shadow-card-hover: 0 2px 6px rgba(24, 28, 40, 0.05), 0 18px 44px rgba(24, 28, 40, 0.10);
  --shadow-lg: 0 24px 64px rgba(24, 28, 40, 0.12);
  --font-body: "Noto Sans SC", "Source Han Sans SC", "Source Han Sans CN", "MiSans", "HarmonyOS Sans SC", system-ui, -apple-system, "Segoe UI", sans-serif;
  --font-head: "Noto Sans SC Medium", "Noto Sans SC", "Source Han Sans SC Medium", "Source Han Sans SC", "MiSans", "HarmonyOS Sans SC", system-ui, sans-serif;
}

* { margin: 0; padding: 0; box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  font-family: var(--font-body);
  font-size: 14px;
  background: var(--bg);
  color: var(--ink);
  line-height: 1.7;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
}

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

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

::selection { background: rgba(37, 99, 235, 0.14); }

h1, h2, h3, .stat-num, .fc-text strong, .brand, summary, .vs-title {
  font-family: var(--font-head);
  font-weight: 500;
}

/* ============ 滚动显现 ============ */
.reveal {
  opacity: 0;
  transform: translateY(18px);
  transition: opacity 0.6s cubic-bezier(0.22, 0.61, 0.36, 1),
              transform 0.6s cubic-bezier(0.22, 0.61, 0.36, 1);
  will-change: opacity, transform;
}
.reveal.visible { opacity: 1; transform: none; }

/* ============ 导航 ============ */
.nav {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.88);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border-bottom: 1px solid transparent;
  transition: border-color 0.3s ease, box-shadow 0.3s ease;
}
.nav.scrolled {
  border-bottom-color: var(--line);
  box-shadow: 0 4px 20px rgba(24, 28, 40, 0.04);
}
.nav-inner {
  max-width: 1200px;
  margin: 0 auto;
  padding: 12px 24px;
  display: flex;
  align-items: center;
  gap: 28px;
}
.brand {
  display: flex;
  align-items: center;
  gap: 9px;
  font-size: 15.5px;
  letter-spacing: 0.3px;
  color: var(--ink);
}
.brand-icon { width: 23px; height: 23px; color: var(--accent); }
.nav-links { display: flex; gap: 30px; margin-left: auto; }
.nav-links a {
  font-size: 14px;
  color: var(--body);
  transition: color 0.2s ease;
}
.nav-links a:hover { color: var(--ink); }
.nav-cta {
  font-size: 13.5px;
  padding: 8px 20px;
  border-radius: 999px;
  background: var(--ink);
  color: #fff;
  transition: background 0.2s ease, transform 0.2s ease;
}
.nav-cta:hover { background: #2c3345; transform: translateY(-1px); }
.nav-cta:active { transform: scale(0.97); }

/* ============ 按钮 ============ */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 7px;
  font-size: 14px;
  font-weight: 500;
  line-height: 1;
  padding: 12px 26px;
  border-radius: 999px;
  transition: transform 0.2s ease, box-shadow 0.2s ease, background 0.2s ease, border-color 0.2s ease;
}
.btn:active { transform: scale(0.97); }
.btn svg { width: 15px; height: 15px; }
.btn-ink {
  background: var(--ink);
  color: #fff;
  box-shadow: 0 6px 18px rgba(24, 28, 40, 0.18);
}
.btn-ink:hover {
  background: #2c3345;
  transform: translateY(-1px);
  box-shadow: 0 10px 24px rgba(24, 28, 40, 0.22);
}
.btn-ink svg { transition: transform 0.2s ease; }
.btn-ink:hover svg { transform: translateX(3px); }
.btn-ghost {
  background: var(--bg);
  border: 1px solid var(--line);
  color: var(--ink);
}
.btn-ghost:hover { border-color: #c6cdd8; transform: translateY(-1px); }
.btn-line {
  background: transparent;
  border: 1px solid #c3cad6;
  color: var(--ink);
}
.btn-line:hover { border-color: var(--ink); transform: translateY(-1px); }

/* ============ Hero ============ */
.hero {
  position: relative;
  padding: 138px 24px 88px;
  overflow: hidden;
  background: var(--bg);
}
.hero-bg { position: absolute; inset: 0; pointer-events: none; }
.hero-mesh {
  position: absolute;
  inset: -20% -10% auto;
  height: 90%;
  background:
    radial-gradient(38% 55% at 30% 40%, rgba(124, 108, 240, 0.10), transparent 70%),
    radial-gradient(34% 50% at 68% 30%, rgba(56, 189, 248, 0.09), transparent 70%),
    radial-gradient(26% 42% at 50% 62%, rgba(236, 114, 187, 0.05), transparent 70%);
  filter: blur(46px);
}
.hero-grid {
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(24, 28, 40, 0.028) 1px, transparent 1px),
    linear-gradient(90deg, rgba(24, 28, 40, 0.028) 1px, transparent 1px);
  background-size: 44px 44px;
  mask-image: radial-gradient(ellipse 85% 62% at 50% 0%, #000 28%, transparent 74%);
  -webkit-mask-image: radial-gradient(ellipse 85% 62% at 50% 0%, #000 28%, transparent 74%);
}
.hero-inner {
  position: relative;
  max-width: 1200px;
  margin: 0 auto;
  text-align: center;
}
.hero-title {
  font-size: clamp(32px, 4.2vw, 48px);
  line-height: 1.3;
  letter-spacing: 0.5px;
  color: var(--ink);
}
.hero-sub {
  margin: 18px auto 0;
  max-width: 620px;
  font-size: 15px;
  color: var(--body);
}
.type-wrap {
  display: inline-block;
  min-width: 200px;
  text-align: left;
  color: var(--accent);
  font-weight: 500;
}
.caret {
  display: inline-block;
  width: 2px;
  height: 1.05em;
  margin-left: 2px;
  vertical-align: -0.15em;
  background: var(--accent);
  animation: caretBlink 1s steps(1) infinite;
}
@keyframes caretBlink { 50% { opacity: 0; } }
.hero-actions {
  margin-top: 28px;
  display: flex;
  gap: 12px;
  justify-content: center;
  flex-wrap: wrap;
}

/* ---- Hero 分层展示 ---- */
.hero-shot {
  position: relative;
  max-width: 980px;
  margin: 56px auto 0;
  animation: floatY 8s ease-in-out infinite;
}
@keyframes floatY {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-7px); }
}
.float-card {
  position: absolute;
  z-index: 3;
  display: flex;
  align-items: center;
  gap: 10px;
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  border: 1px solid rgba(24, 28, 40, 0.06);
  border-radius: 10px;
  box-shadow: 0 10px 30px rgba(24, 28, 40, 0.10);
  animation: floatCard 6s ease-in-out infinite;
}
@keyframes floatCard {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-9px); }
}
.fc-chip {
  top: 40px;
  left: -30px;
  padding: 8px 15px;
  gap: 7px;
  font-size: 13px;
  font-weight: 500;
  color: var(--accent);
  animation-delay: 1.2s;
}
.fc-chip svg { width: 17px; height: 17px; }
.fc-topright {
  top: 92px;
  right: -42px;
  padding: 11px 16px;
  animation-delay: 0.4s;
}
.fc-bottomleft {
  bottom: 60px;
  left: -48px;
  padding: 11px 16px;
  animation-delay: 2s;
}
.fc-bottomleft > svg { width: 21px; height: 21px; color: var(--accent); flex-shrink: 0; }
.fc-dot {
  width: 8px; height: 8px;
  border-radius: 50%;
  background: #22c55e;
  box-shadow: 0 0 0 4px rgba(34, 197, 94, 0.14);
  flex-shrink: 0;
}
.fc-text { text-align: left; line-height: 1.4; }
.fc-text strong { display: block; font-size: 13px; color: var(--ink); }
.fc-text small { font-size: 12px; color: var(--muted); }

/* ============ 窗口拟物框 ============ */
.window {
  border: 1px solid rgba(24, 28, 40, 0.07);
  border-radius: 12px;
  background: var(--bg);
  box-shadow: var(--shadow-lg), var(--shadow-sm);
  overflow: hidden;
  text-align: left;
}
.window-bar {
  display: flex;
  align-items: center;
  gap: 7px;
  padding: 10px 15px;
  background: var(--bg-alt);
  border-bottom: 1px solid var(--line);
}
.dot { width: 9px; height: 9px; border-radius: 50%; background: #d6dae2; }
.window-title {
  margin-left: 9px;
  font-size: 12px;
  color: var(--muted);
  letter-spacing: 0.3px;
}
.window img { width: 100%; }

/* ============ 数据条 ============ */
.stats {
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  background: var(--bg);
}
.stats-inner {
  max-width: 1080px;
  margin: 0 auto;
  padding: 40px 24px;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 24px;
  text-align: center;
}
.stat + .stat { border-left: 1px solid var(--line); }
.stat-num {
  font-size: 38px;
  line-height: 1.15;
  color: var(--ink);
}
.stat-unit { font-size: 16px; color: var(--body); }
.stat-label { margin-top: 4px; font-size: 13px; color: var(--muted); }

/* ============ 通用 Section ============ */
.section {
  max-width: 1200px;
  margin: 0 auto;
  padding: 96px 24px 36px;
}
.section-alt {
  max-width: none;
  background: var(--bg-alt);
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}
.section-alt > * { max-width: 1200px; margin-left: auto; margin-right: auto; }
.section-head { text-align: center; margin-bottom: 48px; }
.kicker {
  font-size: 13px;
  letter-spacing: 5px;
  color: var(--accent);
  margin-bottom: 12px;
}
.section-head h2 {
  font-size: clamp(24px, 3vw, 34px);
  line-height: 1.4;
  letter-spacing: 0.5px;
  color: var(--ink);
}
.section-sub {
  margin: 12px auto 0;
  max-width: 620px;
  color: var(--muted);
  font-size: 14.5px;
}

/* ============ 角标与箭头链接 ============ */
.feat-tag {
  display: inline-block;
  align-self: flex-start;
  flex-shrink: 0;
  font-size: 12px;
  line-height: 1;
  padding: 5px 10px;
  border-radius: 6px;
  background: #f1f3f7;
  color: var(--muted);
  margin-bottom: 14px;
}
.feat-tag-w { background: rgba(255, 255, 255, 0.18); color: #fff; }
.feat-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 13.5px;
  color: var(--ink);
  margin-top: auto;
  padding-top: 14px;
  transition: color 0.2s ease;
}
.feat-link svg { width: 14px; height: 14px; transition: transform 0.2s ease; }
.feat-link:hover { color: var(--accent); }
.feat-link:hover svg { transform: translateX(3px); }
.feat-link-w { color: #fff; padding-top: 18px; }
.feat-link-w:hover { color: rgba(255, 255, 255, 0.85); }

/* ============ 功能区：双大卡 + 四小卡 + 宽条 ============ */
.feat-duo {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
}
.feat-card {
  position: relative;
  display: flex;
  flex-direction: column;
  border-radius: 12px;
  padding: 30px 30px 26px;
  overflow: hidden;
  background: var(--bg);
  box-shadow: var(--shadow-card);
  border: 1px solid rgba(24, 28, 40, 0.04);
  transition: transform 0.25s ease, box-shadow 0.25s ease;
}
.feat-card:hover { transform: translateY(-3px); box-shadow: var(--shadow-card-hover); }
.feat-card h3 { font-size: 19px; margin-bottom: 8px; color: var(--ink); }
.feat-card p { font-size: 13.5px; color: var(--body); line-height: 1.75; }
.feat-featured {
  background: linear-gradient(118deg, #2f6bdf 0%, #4d5ae0 55%, #6f63e6 100%);
  border: none;
}
.feat-featured h3 { color: #fff; }
.feat-featured p { color: rgba(255, 255, 255, 0.86); }
.feat-orb {
  position: absolute;
  right: -90px;
  top: -90px;
  width: 300px;
  height: 300px;
  border-radius: 50%;
  border: 1px solid rgba(255, 255, 255, 0.22);
  background: radial-gradient(circle at 30% 30%, rgba(255, 255, 255, 0.12), transparent 60%);
  pointer-events: none;
}
.feat-light { background: linear-gradient(180deg, #ffffff 0%, #f2f6ff 100%); }
.feat-media {
  margin-top: auto;
  padding-top: 18px;
}
.feat-media img {
  width: 100%;
  height: 205px;
  object-fit: cover;
  object-position: top;
  border-radius: 8px;
  border: 1px solid rgba(24, 28, 40, 0.06);
}
.feat-grid4 {
  margin-top: 16px;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 16px;
}
.fcard {
  display: flex;
  flex-direction: column;
  background: var(--bg);
  border: 1px solid rgba(24, 28, 40, 0.04);
  border-radius: 12px;
  padding: 24px 22px;
  box-shadow: var(--shadow-sm);
  transition: transform 0.25s ease, box-shadow 0.25s ease;
}
.fcard:hover { transform: translateY(-3px); box-shadow: var(--shadow-card); }
.fcard h3 { font-size: 16px; margin-bottom: 7px; color: var(--ink); }
.fcard p { font-size: 13px; color: var(--muted); line-height: 1.75; }
.feat-wide {
  margin-top: 16px;
  display: flex;
  align-items: center;
  gap: 28px;
  flex-wrap: wrap;
  background: var(--bg);
  border: 1px solid rgba(24, 28, 40, 0.04);
  border-radius: 12px;
  padding: 26px 30px;
  box-shadow: var(--shadow-sm);
}
.feat-wide-text { flex: 1 1 300px; }
.feat-wide-text h3 { font-size: 17px; margin-bottom: 6px; color: var(--ink); }
.feat-wide-text p { font-size: 13.5px; color: var(--muted); }
.feat-wide-chips {
  flex: 1.4 1 340px;
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}
.chip {
  font-size: 12.5px;
  color: var(--body);
  background: var(--bg-alt);
  border: 1px solid var(--line);
  border-radius: 999px;
  padding: 6px 14px;
  transition: border-color 0.2s ease, color 0.2s ease;
}
.chip:hover { border-color: rgba(37, 99, 235, 0.4); color: var(--accent); }

/* ============ 使用对比 ============ */
.vs-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  max-width: 980px;
  margin: 0 auto;
}
.vs-col {
  background: var(--bg);
  border: 1px solid rgba(24, 28, 40, 0.04);
  border-radius: 12px;
  padding: 26px 26px;
  box-shadow: var(--shadow-sm);
}
.vs-new {
  border-color: rgba(37, 99, 235, 0.22);
  box-shadow: 0 14px 36px rgba(37, 99, 235, 0.08);
}
.vs-title { font-size: 15.5px; color: var(--ink); margin-bottom: 14px; }
.vs-new .vs-title { color: var(--accent); }
.vs-item {
  display: flex;
  gap: 10px;
  align-items: flex-start;
  font-size: 13.5px;
  color: var(--body);
  margin-bottom: 12px;
}
.vs-item:last-child { margin-bottom: 0; }
.vs-item svg { width: 17px; height: 17px; flex-shrink: 0; margin-top: 3.5px; }
.vs-old .vs-item svg { color: #cfd5de; }
.vs-new .vs-item svg { color: var(--accent); }

/* ============ 界面实拍画廊 ============ */
.gallery { padding-bottom: 30px; }
.gallery-viewer { max-width: 980px; margin: 0 auto; }
.gallery-stage {
  position: relative;
  aspect-ratio: 16 / 9;
  background: var(--bg-alt);
}
.gallery-stage img {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: contain;
  opacity: 1;
  transition: opacity 0.4s ease;
}
.gallery-stage img.fading { opacity: 0; }
.gallery-tabs {
  margin: 8px auto 0;
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  column-gap: 34px;
  row-gap: 2px;
  max-width: 980px;
}
.gtab {
  font-family: var(--font-body);
  font-size: 14px;
  color: var(--muted);
  background: none;
  border: none;
  border-bottom: 2px solid transparent;
  padding: 12px 2px 10px;
  cursor: pointer;
  transition: color 0.2s ease, border-color 0.2s ease;
}
.gtab:hover { color: var(--ink); }
.gtab.active {
  color: var(--ink);
  border-bottom-color: var(--ink);
}

/* ============ 常见问题 ============ */
.faq { max-width: 760px; margin: 0 auto; padding-bottom: 20px; }
.faq details {
  background: var(--bg);
  border: 1px solid rgba(24, 28, 40, 0.04);
  border-radius: 12px;
  padding: 2px 22px;
  margin-bottom: 10px;
  box-shadow: var(--shadow-sm);
  transition: border-color 0.2s ease, box-shadow 0.2s ease;
}
.faq details[open] {
  border-color: rgba(37, 99, 235, 0.22);
  box-shadow: 0 10px 28px rgba(37, 99, 235, 0.06);
}
.faq summary {
  cursor: pointer;
  list-style: none;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 15px 0;
  font-size: 14.5px;
  color: var(--ink);
}
.faq summary::-webkit-details-marker { display: none; }
.faq-x {
  width: 17px;
  height: 17px;
  flex-shrink: 0;
  color: var(--faint);
  transition: transform 0.25s ease, color 0.25s ease;
}
.faq details[open] .faq-x { transform: rotate(45deg); color: var(--accent); }
.faq details p {
  padding: 0 30px 16px 0;
  color: var(--muted);
  font-size: 13.5px;
}

/* ============ CTA ============ */
#about { padding-bottom: 16px; }
.cta-panel {
  position: relative;
  overflow: hidden;
  border-radius: 16px;
  background: linear-gradient(120deg, #eef4ff 0%, #f0edff 55%, #fdf2f8 130%);
  border: 1px solid rgba(37, 99, 235, 0.10);
  padding: 58px 48px;
  text-align: center;
}
.cta-deco {
  position: absolute;
  border-radius: 50%;
  border: 1px solid rgba(37, 99, 235, 0.14);
  pointer-events: none;
}
.cta-deco-a { width: 380px; height: 380px; top: -200px; left: -110px; }
.cta-deco-b { width: 300px; height: 300px; bottom: -180px; right: -70px; }
.cta-panel h2 {
  position: relative;
  font-size: clamp(24px, 3vw, 34px);
  letter-spacing: 0.5px;
  line-height: 1.4;
  color: var(--ink);
}
.cta-panel p {
  position: relative;
  margin: 12px auto 0;
  max-width: 580px;
  font-size: 14px;
  color: var(--body);
}
.cta-actions {
  position: relative;
  margin-top: 26px;
  display: flex;
  gap: 12px;
  justify-content: center;
  flex-wrap: wrap;
}

/* ============ 页脚 ============ */
.footer {
  margin-top: 80px;
  border-top: 1px solid var(--line);
  background: var(--bg-alt);
}
.footer-inner {
  max-width: 1200px;
  margin: 0 auto;
  padding: 48px 24px 0;
}
.footer-top {
  display: grid;
  grid-template-columns: 1.6fr 1fr 1fr;
  gap: 40px;
  padding-bottom: 40px;
}
.footer-brand {
  display: inline-flex;
  align-items: center;
  gap: 9px;
  font-size: 14.5px;
  color: var(--ink);
}
.footer-desc { margin-top: 12px; color: var(--muted); font-size: 13px; max-width: 400px; }
.footer-col { display: flex; flex-direction: column; gap: 9px; }
.footer-col-title {
  font-size: 12.5px;
  letter-spacing: 2px;
  color: var(--faint);
  margin-bottom: 4px;
}
.footer-col a { font-size: 13.5px; color: var(--body); transition: color 0.2s ease; }
.footer-col a:hover { color: var(--accent); }
.footer-bottom {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
  border-top: 1px solid var(--line);
  padding: 16px 0 20px;
  color: var(--faint);
  font-size: 12px;
}

/* ============ 响应式 ============ */
@media (max-width: 1024px) {
  .feat-grid4 { grid-template-columns: repeat(2, 1fr); }
  .fc-chip, .fc-topright, .fc-bottomleft { display: none; }
  .stat + .stat { border-left: none; }
}
@media (max-width: 720px) {
  .nav-links { display: none; }
  .stats-inner { grid-template-columns: repeat(2, 1fr); }
  .feat-duo { grid-template-columns: 1fr; }
  .feat-grid4 { grid-template-columns: 1fr; }
  .vs-grid { grid-template-columns: 1fr; }
  .footer-top { grid-template-columns: 1fr; gap: 26px; }
  .hero { padding-top: 118px; }
  .type-wrap { min-width: 0; }
  .cta-panel { padding: 44px 24px; }
  .gallery-tabs { column-gap: 20px; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .reveal { transition: none; opacity: 1; transform: none; }
  .hero-shot, .float-card, .caret { animation: none; }
}