/* =====================================================
   KEFENG AI
   Global Design System
===================================================== */

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

:root {
  --black: #07090d;
  --dark: #0d1117;
  --dark-2: #151a22;

  --text: #111827;
  --text-light: #475467;
  --muted: #667085;

  --blue: #2563eb;
  --blue-light: #60a5fa;

  --white: #ffffff;
  --light: #f7f8fa;

  --line: #e6e8ec;
  --line-dark: rgba(255, 255, 255, 0.12);

  --max-width: 1160px;

  --radius: 14px;
}


/* =====================================================
   Base
===================================================== */

html {
  scroll-behavior: smooth;
}

body {
  font-family:
    -apple-system,
    BlinkMacSystemFont,
    "SF Pro Display",
    "SF Pro Text",
    "Helvetica Neue",
    Arial,
    "PingFang SC",
    "Microsoft YaHei",
    sans-serif;

  color: var(--text);
  background: var(--white);

  line-height: 1.7;

  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

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

button {
  font: inherit;
}

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


/* =====================================================
   Layout
===================================================== */

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

  margin: 0 auto;
}


/* =====================================================
   Header
===================================================== */

.site-header {
  position: sticky;

  top: 0;
  z-index: 1000;

  background:
    rgba(255, 255, 255, 0.86);

  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);

  border-bottom:
    1px solid rgba(0, 0, 0, 0.06);
}


.nav {
  height: 72px;

  display: flex;

  align-items: center;
  justify-content: space-between;
}


/* Logo */

.logo {
  display: inline-flex;

  align-items: center;

  gap: 5px;

  font-size: 21px;
  font-weight: 800;

  letter-spacing: -0.8px;
}

.logo-main {
  color: var(--black);
}

.logo-ai {
  color: var(--blue);
}


/* Navigation */

nav {
  display: flex;

  align-items: center;

  gap: 34px;
}

nav a {
  position: relative;

  color: var(--text-light);

  font-size: 14px;
  font-weight: 500;

  transition:
    color 0.2s ease;
}

nav a::after {
  content: "";

  position: absolute;

  left: 0;
  right: 0;
  bottom: -8px;

  height: 2px;

  background: var(--blue);

  transform: scaleX(0);

  transform-origin: center;

  transition:
    transform 0.2s ease;
}

nav a:hover {
  color: var(--blue);
}

nav a:hover::after {
  transform: scaleX(1);
}


/* Mobile menu */

.menu-toggle {
  display: none;

  width: 42px;
  height: 42px;

  border: 1px solid var(--line);
  border-radius: 8px;

  background: white;

  color: var(--text);

  cursor: pointer;
}


/* =====================================================
   Typography
===================================================== */

h1,
h2,
h3 {
  color: var(--black);

  font-weight: 700;

  letter-spacing: -1.5px;
}

h1 {
  font-size: clamp(48px, 6.5vw, 76px);

  line-height: 1.08;

  letter-spacing: -3.5px;
}

h2 {
  font-size: clamp(38px, 5vw, 52px);

  line-height: 1.15;

  letter-spacing: -2.5px;
}

h3 {
  font-size: 22px;

  line-height: 1.3;

  letter-spacing: -0.7px;
}


/* =====================================================
   Eyebrow
===================================================== */

.eyebrow {
  margin-bottom: 20px;

  color: var(--blue);

  font-size: 11px;

  font-weight: 700;

  letter-spacing: 2.5px;

  text-transform: uppercase;
}


/* =====================================================
   Hero
===================================================== */

.hero {
  position: relative;

  min-height: 700px;

  display: flex;

  align-items: center;

  overflow: hidden;

  background:
    radial-gradient(
      circle at 75% 45%,
      rgba(37, 99, 235, 0.12),
      transparent 27%
    ),

    radial-gradient(
      circle at 90% 10%,
      rgba(96, 165, 250, 0.08),
      transparent 25%
    ),

    #ffffff;
}


.hero::before {
  content: "";

  position: absolute;

  width: 500px;
  height: 500px;

  right: -250px;
  top: 80px;

  border:
    1px solid rgba(37, 99, 235, 0.08);

  border-radius: 50%;
}


.hero-grid {
  display: grid;

  grid-template-columns:
    1.08fr
    0.92fr;

  gap: 70px;

  align-items: center;
}


.hero-content {
  position: relative;
  z-index: 2;
}


.hero h1 span {
  color: var(--blue);
}


.hero-description {
  max-width: 650px;

  margin-top: 30px;

  color: var(--muted);

  font-size: 17px;

  line-height: 1.9;
}


.hero-actions {
  display: flex;

  gap: 14px;

  margin-top: 38px;
}


/* =====================================================
   Buttons
===================================================== */

.btn {
  min-height: 48px;

  display: inline-flex;

  align-items: center;
  justify-content: center;

  padding: 0 24px;

  border-radius: 8px;

  font-size: 14px;

  font-weight: 600;

  transition:
    transform 0.2s ease,
    background 0.2s ease,
    border-color 0.2s ease,
    color 0.2s ease;
}


.btn:hover {
  transform: translateY(-2px);
}


.btn-primary {
  color: white;

  background: var(--blue);

  box-shadow:
    0 8px 24px rgba(37, 99, 235, 0.22);
}


.btn-primary:hover {
  background: #1d4ed8;
}


.btn-secondary {
  color: var(--text);

  background: white;

  border:
    1px solid var(--line);
}


.btn-secondary:hover {
  color: var(--blue);

  border-color:
    rgba(37, 99, 235, 0.35);
}


/* =====================================================
   Hero AI Visual
===================================================== */

.hero-visual {
  position: relative;

  height: 460px;

  display: flex;

  align-items: center;
  justify-content: center;
}


.ai-core {
  position: relative;

  z-index: 10;

  width: 150px;
  height: 150px;

  display: flex;

  flex-direction: column;

  align-items: center;
  justify-content: center;

  border-radius: 50%;

  background:
    radial-gradient(
      circle at 35% 30%,
      #1f2937,
      #05070b 70%
    );

  color: white;

  box-shadow:
    0 0 0 1px rgba(255,255,255,0.05),
    0 20px 70px rgba(37,99,235,0.24),
    0 0 120px rgba(37,99,235,0.14);
}


.ai-core div {
  font-size: 42px;

  font-weight: 800;

  line-height: 1;

  letter-spacing: -3px;
}


.ai-core small {
  margin-top: 8px;

  color: #98a2b3;

  font-size: 9px;

  letter-spacing: 3px;
}


/* Orbits */

.ai-orbit {
  position: absolute;

  border:
    1px solid rgba(37, 99, 235, 0.18);

  border-radius: 50%;

  transform: rotate(-15deg);
}


.orbit-1 {
  width: 230px;
  height: 230px;

  border-left-color:
    rgba(37, 99, 235, 0.45);

  animation:
    orbit-spin 16s linear infinite;
}


.orbit-2 {
  width: 340px;
  height: 340px;

  border-right-color:
    rgba(37, 99, 235, 0.40);

  animation:
    orbit-spin 24s linear infinite reverse;
}


.orbit-3 {
  width: 450px;
  height: 450px;

  border-top-color:
    rgba(37, 99, 235, 0.35);

  animation:
    orbit-spin 32s linear infinite;
}


@keyframes orbit-spin {

  from {
    transform:
      rotate(0deg);
  }

  to {
    transform:
      rotate(360deg);
  }

}


/* =====================================================
   Signals
===================================================== */

.signals {
  border-top:
    1px solid var(--line);

  border-bottom:
    1px solid var(--line);

  background: white;
}


.signal-grid {
  display: grid;

  grid-template-columns:
    repeat(4, 1fr);
}


.signal-grid div {
  min-height: 100px;

  display: flex;

  flex-direction: column;

  justify-content: center;

  padding: 22px 28px;

  border-right:
    1px solid var(--line);
}


.signal-grid div:last-child {
  border-right: none;
}


.signal-grid strong {
  color: var(--black);

  font-size: 17px;

  font-weight: 700;
}


.signal-grid span {
  margin-top: 3px;

  color: var(--muted);

  font-size: 12px;
}


/* =====================================================
   General Section
===================================================== */

.section {
  padding: 120px 0;
}


.section-heading {
  max-width: 720px;

  margin-bottom: 64px;
}


.section-heading p {
  max-width: 650px;

  margin-top: 22px;

  color: var(--muted);

  font-size: 16px;

  line-height: 1.8;
}


/* =====================================================
   Cards
===================================================== */

.card-grid {
  display: grid;

  grid-template-columns:
    repeat(4, 1fr);

  gap: 18px;
}


.card {
  position: relative;

  min-height: 320px;

  padding: 30px;

  overflow: hidden;

  background: white;

  border:
    1px solid var(--line);

  border-radius:
    var(--radius);

  transition:
    transform 0.25s ease,
    box-shadow 0.25s ease,
    border-color 0.25s ease;
}


.card::before {
  content: "";

  position: absolute;

  left: 0;
  right: 0;
  top: 0;

  height: 2px;

  background:
    linear-gradient(
      90deg,
      transparent,
      var(--blue),
      transparent
    );

  opacity: 0;

  transition:
    opacity 0.25s ease;
}


.card:hover {
  transform:
    translateY(-7px);

  border-color:
    rgba(37, 99, 235, 0.20);

  box-shadow:
    0 24px 60px rgba(16, 24, 40, 0.09);
}


.card:hover::before {
  opacity: 1;
}


.card-number {
  color: var(--blue);

  font-size: 11px;

  font-weight: 700;

  letter-spacing: 1.5px;
}


.card h3 {
  margin-top: 70px;
}


.card p {
  margin-top: 15px;

  color: var(--muted);

  font-size: 13px;

  line-height: 1.8;
}


.card a {
  display: inline-block;

  margin-top: 22px;

  color: var(--blue);

  font-size: 12px;

  font-weight: 600;
}


/* =====================================================
   Dark Section
===================================================== */

.dark-section {
  position: relative;

  padding: 125px 0;

  overflow: hidden;

  background:
    radial-gradient(
      circle at 85% 20%,
      rgba(37, 99, 235, 0.15),
      transparent 30%
    ),

    var(--black);

  color: white;
}


.dark-section::after {
  content: "";

  position: absolute;

  width: 500px;
  height: 500px;

  right: -250px;
  bottom: -300px;

  border:
    1px solid rgba(96, 165, 250, 0.10);

  border-radius: 50%;
}


.dark-section h1,
.dark-section h2,
.dark-section h3 {
  color: white;
}


.dark-grid {
  position: relative;
  z-index: 2;

  display: grid;

  grid-template-columns:
    1.05fr
    0.95fr;

  gap: 100px;

  align-items: center;
}


.dark-text {
  color: #98a2b3;

  font-size: 16px;

  line-height: 1.9;
}


.dark-text p + p {
  margin-top: 24px;
}


/* =====================================================
   CTA
===================================================== */

.cta {
  padding: 120px 0;

  text-align: center;

  background:
    radial-gradient(
      circle at 50% 0%,
      rgba(37, 99, 235, 0.08),
      transparent 35%
    ),

    var(--light);
}


.cta h2 {
  color: var(--black);
}


.cta p {
  max-width: 650px;

  margin: 22px auto 32px;

  color: var(--muted);

  font-size: 16px;
}


/* =====================================================
   Footer
===================================================== */

.footer {
  padding: 54px 0;

  background: #05070b;

  color: white;
}


.footer-grid {
  display: flex;

  align-items: flex-start;

  justify-content: space-between;

  gap: 60px;
}


.footer-logo .logo-main {
  color: white;
}


.footer p {
  margin-top: 8px;

  color: #98a2b3;

  font-size: 12px;
}


/* =====================================================
   Responsive
===================================================== */

@media (max-width: 1000px) {

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

  .hero-grid {
    gap: 30px;
  }

  .hero-visual {
    transform: scale(0.85);
  }

}


@media (max-width: 800px) {

  .container {
    width:
      min(
        100% - 32px,
        var(--max-width)
      );
  }


  /* Navigation */

  nav {
    position: absolute;

    display: none;

    left: 0;
    right: 0;
    top: 72px;

    padding: 22px 24px;

    flex-direction: column;

    align-items: flex-start;

    gap: 20px;

    background: white;

    border-bottom:
      1px solid var(--line);

    box-shadow:
      0 20px 30px rgba(0,0,0,0.06);
  }


  nav.active {
    display: flex;
  }


  .menu-toggle {
    display: flex;

    align-items: center;
    justify-content: center;
  }


  /* Hero */

  .hero {
    min-height: auto;

    padding: 90px 0 70px;
  }


  .hero-grid {
    grid-template-columns: 1fr;

    gap: 30px;
  }


  .hero h1 {
    font-size:
      clamp(44px, 13vw, 60px);

    letter-spacing: -3px;
  }


  .hero-description {
    font-size: 15px;
  }


  .hero-visual {
    height: 360px;

    transform: none;
  }


  .orbit-3 {
    width: 360px;
    height: 360px;
  }


  .orbit-2 {
    width: 280px;
    height: 280px;
  }


  .orbit-1 {
    width: 200px;
    height: 200px;
  }


  /* Signals */

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


  .signal-grid div:nth-child(2) {
    border-right: none;
  }


  .signal-grid div:nth-child(3),
  .signal-grid div:nth-child(4) {
    border-top:
      1px solid var(--line);
  }


  /* Sections */

  .section {
    padding: 85px 0;
  }


  .section-heading {
    margin-bottom: 45px;
  }


  /* Cards */

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


  .card {
    min-height: auto;

    padding: 28px;
  }


  .card h3 {
    margin-top: 45px;
  }


  /* Dark */

  .dark-section {
    padding: 85px 0;
  }


  .dark-grid {
    grid-template-columns: 1fr;

    gap: 45px;
  }


  /* CTA */

  .cta {
    padding: 85px 0;
  }


  /* Footer */

  .footer-grid {
    flex-direction: column;

    gap: 25px;
  }

}


@media (max-width: 520px) {

  .hero-actions {
    flex-direction: column;

    align-items: stretch;
  }


  .btn {
    width: 100%;
  }


  .signal-grid strong {
    font-size: 15px;
  }


  .signal-grid span {
    font-size: 11px;
  }

}