:root {
  --ink: #14201d;
  --muted: #66736d;
  --paper: #f6f5ef;
  --panel: #ffffff;
  --line: #dfe3da;
  --accent: #0f7d68;
  --accent-dark: #0b574b;
  --blueprint: #2f5f83;
  --warm: #c48648;
  --shadow: 0 18px 48px rgba(20, 32, 29, 0.13);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  color: var(--ink);
  background: var(--paper);
  font-family: "Microsoft YaHei", "PingFang SC", "Noto Sans SC", Arial, sans-serif;
  line-height: 1.65;
}

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

.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  min-height: 72px;
  padding: 14px clamp(20px, 5vw, 72px);
  background: rgba(246, 245, 239, 0.92);
  border-bottom: 1px solid rgba(223, 227, 218, 0.9);
  backdrop-filter: blur(14px);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-size: 18px;
  font-weight: 900;
  white-space: nowrap;
}

.brand-mark {
  display: grid;
  width: 38px;
  height: 38px;
  place-items: center;
  color: #fff;
  background: var(--accent);
  border-radius: 8px;
  font-size: 15px;
}

.nav {
  display: flex;
  align-items: center;
  gap: clamp(16px, 3vw, 34px);
  color: var(--muted);
  font-size: 15px;
}

.nav a:hover {
  color: var(--accent-dark);
}

.hero {
  min-height: calc(100vh - 118px);
  display: grid;
  align-items: center;
  padding: 78px clamp(20px, 5vw, 72px);
  color: #fff;
  background:
    linear-gradient(90deg, rgba(11, 18, 17, 0.9), rgba(11, 18, 17, 0.7) 42%, rgba(11, 18, 17, 0.2)),
    url("assets/su-cad-hero.png") center / cover;
}

.hero-copy {
  max-width: 760px;
}

.eyebrow {
  margin: 0 0 14px;
  color: var(--warm);
  font-size: 13px;
  font-weight: 900;
  letter-spacing: 0;
  text-transform: uppercase;
}

.hero h1,
.section h2,
.contact-section h2 {
  margin: 0;
  line-height: 1.1;
}

.hero h1 {
  font-size: clamp(52px, 9vw, 108px);
  font-weight: 950;
}

.hero p:not(.eyebrow) {
  max-width: 680px;
  margin: 24px 0 0;
  color: rgba(255, 255, 255, 0.9);
  font-size: clamp(18px, 2vw, 24px);
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 14px;
  margin-top: 34px;
}

.pay-form {
  margin: 0;
}

.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 46px;
  padding: 0 22px;
  border: 1px solid transparent;
  border-radius: 8px;
  font: inherit;
  font-weight: 900;
  cursor: pointer;
}

.button.primary {
  color: #fff;
  background: var(--accent);
}

.button.primary:hover {
  background: var(--accent-dark);
}

.button.secondary {
  color: #fff;
  border-color: rgba(255, 255, 255, 0.55);
}

.button.secondary:hover {
  background: rgba(255, 255, 255, 0.12);
}

.section {
  padding: 80px clamp(20px, 5vw, 72px);
}

.section-heading {
  max-width: 780px;
  margin-bottom: 30px;
}

.section h2,
.contact-section h2 {
  font-size: clamp(30px, 5vw, 50px);
}

.workflow-grid,
.output-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 20px;
}

.workflow-grid article,
.output-grid article,
.feature-list div {
  min-height: 220px;
  padding: 26px;
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 8px;
  box-shadow: var(--shadow);
}

.workflow-grid span {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 48px;
  height: 48px;
  margin-bottom: 28px;
  color: #fff;
  background: var(--blueprint);
  border-radius: 8px;
  font-weight: 900;
}

.workflow-grid article:nth-child(2) span {
  background: var(--accent);
}

.workflow-grid article:nth-child(3) span {
  background: var(--warm);
}

h3 {
  margin: 0 0 10px;
  font-size: 23px;
}

p {
  margin: 0;
}

.workflow-grid p,
.output-grid p,
.feature-list p,
.feature-copy p,
.contact-section p {
  color: var(--muted);
}

.feature-section {
  display: grid;
  grid-template-columns: minmax(0, 0.85fr) minmax(0, 1.15fr);
  gap: clamp(28px, 6vw, 72px);
  background: #fff;
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}

.feature-list {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 18px;
}

.feature-list div {
  min-height: 168px;
  box-shadow: none;
}

.output-grid {
  grid-template-columns: repeat(4, minmax(0, 1fr));
}

.contact-section {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 28px;
  margin: 70px clamp(20px, 5vw, 72px);
  padding: 42px;
  color: #fff;
  background: var(--ink);
  border-radius: 8px;
}

.contact-section p {
  max-width: 760px;
  margin-top: 14px;
  color: rgba(255, 255, 255, 0.78);
}

.site-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
  padding: 26px clamp(20px, 5vw, 72px);
  color: var(--muted);
  border-top: 1px solid var(--line);
}

@media (max-width: 900px) {
  .site-header,
  .contact-section,
  .site-footer {
    align-items: flex-start;
    flex-direction: column;
  }

  .hero {
    min-height: 74vh;
  }

  .workflow-grid,
  .feature-section,
  .feature-list,
  .output-grid {
    grid-template-columns: 1fr;
  }

  .workflow-grid article,
  .output-grid article,
  .feature-list div {
    min-height: auto;
  }
}

@media (max-width: 520px) {
  .nav {
    width: 100%;
    justify-content: space-between;
  }

  .hero h1 {
    font-size: 48px;
  }

  .button {
    width: 100%;
  }

  .pay-form {
    width: 100%;
  }
}