:root {
  --background: #07111f;
  --background-secondary: #091827;
  --surface: #0c1d2e;
  --accent: #3a83f7;
  --accent-light: #4da3ff;
  --text-primary: #ffffff;
  --text-secondary: #b7c7dc;
  --border: rgba(183, 199, 220, 0.18);
  --header-height: 78px;
  --max-width: 1160px;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  scroll-padding-top: var(--header-height);
}

body {
  margin: 0;
  overflow-x: hidden;
  color: var(--text-primary);
  background: var(--background);
  font-family: Inter, "PingFang SC", "Microsoft YaHei", system-ui, -apple-system, sans-serif;
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

a {
  color: inherit;
}

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

.container {
  width: min(calc(100% - 48px), var(--max-width));
  margin-inline: auto;
}

.skip-link {
  position: fixed;
  z-index: 1000;
  top: 10px;
  left: 10px;
  padding: 8px 14px;
  color: #07111f;
  background: #fff;
  border-radius: 6px;
  transform: translateY(-150%);
}

.skip-link:focus {
  transform: translateY(0);
}

.site-header {
  position: fixed;
  z-index: 100;
  inset: 0 0 auto;
  height: var(--header-height);
  border-bottom: 1px solid transparent;
  transition: background-color 180ms ease, border-color 180ms ease, box-shadow 180ms ease;
}

.site-header.is-scrolled,
.site-header.menu-open {
  background: rgba(7, 17, 31, 0.94);
  border-color: var(--border);
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.18);
  backdrop-filter: blur(14px);
}

.header-inner {
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 11px;
  text-decoration: none;
}

.brand-copy {
  display: grid;
  line-height: 1.2;
}

.brand-copy strong {
  font-size: 1rem;
  letter-spacing: 0.04em;
}

.brand-copy small {
  margin-top: 5px;
  color: var(--text-secondary);
  font-size: 0.68rem;
  letter-spacing: 0.12em;
}

.site-nav {
  display: flex;
  align-items: center;
  gap: 30px;
}

.site-nav a {
  position: relative;
  padding: 8px 0;
  color: var(--text-secondary);
  font-size: 0.9rem;
  text-decoration: none;
  transition: color 160ms ease;
}

.site-nav a::after {
  position: absolute;
  right: 0;
  bottom: 2px;
  left: 0;
  height: 1px;
  background: var(--accent-light);
  content: "";
  transform: scaleX(0);
  transition: transform 160ms ease;
}

.site-nav a:hover,
.site-nav a:focus-visible {
  color: var(--text-primary);
}

.site-nav a:hover::after,
.site-nav a:focus-visible::after {
  transform: scaleX(1);
}

.nav-toggle {
  display: none;
  width: 42px;
  height: 42px;
  padding: 10px;
  border: 1px solid var(--border);
  border-radius: 8px;
  color: inherit;
  background: rgba(255, 255, 255, 0.04);
  cursor: pointer;
}

.nav-toggle span {
  display: block;
  height: 2px;
  margin: 4px 0;
  background: currentColor;
  transition: transform 180ms ease, opacity 180ms ease;
}

.hero {
  position: relative;
  min-height: 760px;
  display: flex;
  align-items: center;
  background: var(--background) url("../assets/images/hero.jpg") center / cover no-repeat;
  isolation: isolate;
}

.hero-overlay {
  position: absolute;
  z-index: -1;
  inset: 0;
  background:
    linear-gradient(90deg, rgba(7, 17, 31, 0.98) 0%, rgba(7, 17, 31, 0.83) 40%, rgba(7, 17, 31, 0.18) 75%),
    linear-gradient(0deg, var(--background) 0%, transparent 22%);
}

.hero-content {
  padding-top: var(--header-height);
}

.eyebrow,
.section-label {
  margin: 0 0 14px;
  color: var(--accent-light);
  font-size: 0.76rem;
  font-weight: 700;
  letter-spacing: 0.22em;
}

.hero h1 {
  max-width: 700px;
  margin: 0;
  font-size: clamp(3rem, 7vw, 5.8rem);
  font-weight: 700;
  line-height: 1.08;
  letter-spacing: -0.045em;
}

.hero-intro {
  margin: 28px 0 34px;
  color: var(--text-secondary);
  font-size: clamp(1rem, 1.7vw, 1.14rem);
}

.button {
  display: inline-flex;
  align-items: center;
  gap: 16px;
  padding: 11px 1px;
  border-bottom: 1px solid var(--accent-light);
  color: var(--text-primary);
  font-size: 0.92rem;
  text-decoration: none;
}

.button span {
  color: var(--accent-light);
}

.section {
  padding: 120px 0;
}

.about {
  border-bottom: 1px solid var(--border);
}

.about-grid {
  display: grid;
  grid-template-columns: minmax(220px, 0.8fr) minmax(0, 1.4fr);
  gap: 80px;
}

h2 {
  margin: 0;
  font-size: clamp(2rem, 4vw, 3.2rem);
  line-height: 1.2;
  letter-spacing: -0.03em;
}

.about-copy {
  max-width: 690px;
  color: var(--text-secondary);
  font-size: 1.08rem;
}

.about-copy p {
  margin: 0 0 1.2em;
}

.explorations {
  background: var(--background-secondary);
}

.section-heading {
  margin-bottom: 54px;
}

.section-heading > p:last-child {
  margin: 16px 0 0;
  color: var(--text-secondary);
}

.card-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 18px;
}

.topic-card {
  min-height: 260px;
  padding: 32px 28px;
  border: 1px solid var(--border);
  border-radius: 4px;
  background: rgba(255, 255, 255, 0.018);
  transition: border-color 180ms ease, background-color 180ms ease, transform 180ms ease;
}

.topic-card:hover {
  border-color: rgba(77, 163, 255, 0.48);
  background: rgba(77, 163, 255, 0.045);
  transform: translateY(-3px);
}

.topic-card img {
  width: 38px;
  height: 38px;
  margin-bottom: 62px;
}

.topic-card h3 {
  margin: 0 0 10px;
  font-size: 1.15rem;
}

.topic-card p {
  margin: 0;
  color: var(--text-secondary);
  font-size: 0.9rem;
}

.site-footer {
  padding: 28px 0;
  background: #050d17;
}

.footer-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  color: var(--text-secondary);
  font-size: 0.78rem;
}

.footer-inner p {
  margin: 0;
}

.icp-link {
  text-underline-offset: 4px;
  text-decoration-color: rgba(183, 199, 220, 0.45);
}

.icp-link:hover,
.icp-link:focus-visible {
  color: var(--text-primary);
  text-decoration-color: var(--accent-light);
}

:focus-visible {
  outline: 2px solid var(--accent-light);
  outline-offset: 4px;
}

@media (max-width: 900px) {
  .site-nav {
    gap: 20px;
  }

  .card-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .about-grid {
    grid-template-columns: 1fr;
    gap: 34px;
  }
}

@media (max-width: 720px) {
  :root {
    --header-height: 68px;
  }

  .container {
    width: min(calc(100% - 36px), var(--max-width));
  }

  .brand-copy small {
    display: none;
  }

  .nav-toggle {
    display: block;
  }

  .nav-toggle[aria-expanded="true"] span:nth-child(1) {
    transform: translateY(6px) rotate(45deg);
  }

  .nav-toggle[aria-expanded="true"] span:nth-child(2) {
    opacity: 0;
  }

  .nav-toggle[aria-expanded="true"] span:nth-child(3) {
    transform: translateY(-6px) rotate(-45deg);
  }

  .site-nav {
    position: absolute;
    top: var(--header-height);
    right: 0;
    left: 0;
    display: grid;
    gap: 0;
    padding: 8px 18px 18px;
    background: rgba(7, 17, 31, 0.98);
    border-bottom: 1px solid var(--border);
    visibility: hidden;
    opacity: 0;
    transform: translateY(-8px);
    transition: opacity 160ms ease, transform 160ms ease, visibility 160ms;
  }

  .site-nav.is-open {
    visibility: visible;
    opacity: 1;
    transform: translateY(0);
  }

  .site-nav a {
    padding: 12px 6px;
    border-bottom: 1px solid rgba(183, 199, 220, 0.1);
  }

  .hero {
    min-height: 700px;
    background-position: 63% center;
  }

  .hero-overlay {
    background:
      linear-gradient(90deg, rgba(7, 17, 31, 0.98) 0%, rgba(7, 17, 31, 0.78) 65%, rgba(7, 17, 31, 0.35) 100%),
      linear-gradient(0deg, var(--background) 0%, transparent 26%);
  }

  .hero h1 {
    max-width: 520px;
    font-size: clamp(2.8rem, 13vw, 4.5rem);
  }

  .section {
    padding: 86px 0;
  }

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

  .topic-card {
    min-height: 220px;
  }

  .topic-card img {
    margin-bottom: 42px;
  }

  .footer-inner {
    flex-direction: column;
    align-items: flex-start;
    gap: 8px;
  }
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  *,
  *::before,
  *::after {
    scroll-behavior: auto !important;
    transition-duration: 0.01ms !important;
  }
}