/* ====== CSS Custom Properties ====== */
:root {
  --color-primary: #1e3a5f;
  --color-primary-light: #2d5a8e;
  --color-green: #22c55e;
  --color-yellow: #eab308;
  --color-red: #ef4444;
  --color-bg-dark: #0f172a;
  --color-bg-light: #f8fafc;
  --color-bg-white: #ffffff;
  --color-text: #1e293b;
  --color-text-muted: #64748b;
  --color-border: #e2e8f0;
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Helvetica, Arial, sans-serif;
  --max-width: 1100px;
  --nav-height: 60px;
  --radius: 12px;
  --radius-lg: 20px;
}

/* ====== Reset ====== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }
body {
  font-family: var(--font-sans);
  color: var(--color-text);
  background: var(--color-bg-white);
  line-height: 1.6;
  overflow-x: hidden;
}
a { color: inherit; text-decoration: none; }
ul { list-style: none; }
img { max-width: 100%; display: block; }
button { font: inherit; cursor: pointer; border: none; background: none; }

/* ====== Container ====== */
.container { max-width: var(--max-width); margin: 0 auto; padding: 0 24px; }

/* ====== Section titles ====== */
.section-title {
  font-size: 36px; font-weight: 700; text-align: center;
  color: var(--color-primary); margin-bottom: 12px;
}
.section-desc {
  text-align: center; color: var(--color-text-muted); font-size: 17px;
  max-width: 520px; margin: 0 auto 48px; line-height: 1.7;
}
.section-label { font-size: 20px; font-weight: 700; margin-bottom: 16px; }

/* ====== 1. Nav ====== */
.nav {
  position: fixed; top: 0; left: 0; right: 0; z-index: 1000;
  background: rgba(255,255,255,0.85);
  backdrop-filter: blur(12px); -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid rgba(0,0,0,0.06); transition: box-shadow 0.3s;
}
.nav.scrolled { box-shadow: 0 2px 20px rgba(0,0,0,0.08); }
.nav-inner {
  max-width: var(--max-width); margin: 0 auto; padding: 0 24px;
  height: var(--nav-height); display: flex; align-items: center; gap: 32px;
}
.nav-logo {
  font-size: 20px; font-weight: 700; color: var(--color-primary);
  display: flex; align-items: center; gap: 8px; flex-shrink: 0;
}
.nav-links { display: flex; gap: 8px; flex: 1; justify-content: center; }
.nav-links a {
  padding: 8px 14px; font-size: 14px; color: var(--color-text-muted);
  border-radius: 8px; transition: color 0.2s, background 0.2s;
}
.nav-links a:hover { color: var(--color-primary); background: #f1f5f9; }
.nav-cta {
  flex-shrink: 0; padding: 8px 20px; font-size: 14px; font-weight: 600;
  color: #fff; background: var(--color-primary); border-radius: 20px; transition: background 0.2s;
}
.nav-cta:hover { background: var(--color-primary-light); }

/* Mobile nav toggle */
.nav-toggle { display: none; flex-direction: column; gap: 5px; padding: 8px; }
.nav-toggle span { display: block; width: 22px; height: 2px; background: var(--color-primary); border-radius: 2px; transition: 0.3s; }

/* ====== 2. Hero ====== */
.hero {
  min-height: 100vh; display: flex; align-items: center; justify-content: center;
  position: relative; overflow: hidden;
  background: linear-gradient(160deg, #0f172a 0%, #1e3a5f 50%, #1e3a5f 100%);
}
.hero-bg {
  position: absolute; inset: 0;
  background: radial-gradient(ellipse 60% 50% at 50% 40%, rgba(34,197,94,0.08) 0%, transparent 70%),
              radial-gradient(ellipse 80% 60% at 80% 80%, rgba(59,130,246,0.06) 0%, transparent 60%);
}
.hero-content {
  position: relative; z-index: 1; display: flex; align-items: center;
  justify-content: center; gap: 60px; max-width: var(--max-width);
  margin: 0 auto; padding: 100px 24px 60px;
}
.hero-text { flex: 1; min-width: 0; }
.hero-text h1 { font-size: 48px; font-weight: 800; color: #fff; line-height: 1.25; margin-bottom: 16px; }
.hero-highlight {
  background: linear-gradient(135deg, #22c55e, #4ade80);
  -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text;
}
.hero-sub { font-size: 18px; color: #94a3b8; margin-bottom: 32px; line-height: 1.6; }
.hero-actions { display: flex; gap: 16px; margin-bottom: 40px; flex-wrap: wrap; }
.btn {
  display: inline-flex; align-items: center; gap: 6px;
  padding: 14px 32px; font-size: 16px; font-weight: 600;
  border-radius: 28px; transition: all 0.2s;
}
.btn-primary {
  background: linear-gradient(135deg, #22c55e, #16a34a);
  color: #fff; box-shadow: 0 4px 20px rgba(34,197,94,0.35);
}
.btn-primary:hover { transform: translateY(-2px); box-shadow: 0 6px 28px rgba(34,197,94,0.45); }
.btn-outline { border: 1.5px solid rgba(255,255,255,0.3); color: #cbd5e1; }
.btn-outline:hover { border-color: rgba(255,255,255,0.6); color: #fff; }
.hero-stats { display: flex; gap: 32px; }
.stat { text-align: center; }
.stat strong { display: block; font-size: 28px; font-weight: 800; color: #fff; }
.stat span { font-size: 13px; color: #94a3b8; }
.hero-visual { flex-shrink: 0; }
.hero-drone-svg { width: 300px; height: 320px; }
.hero-scroll-hint {
  position: absolute; bottom: 28px; left: 50%; transform: translateX(-50%);
  display: flex; flex-direction: column; align-items: center; gap: 4px;
  color: #64748b; font-size: 12px; animation: bounce 2s infinite;
}
@keyframes bounce {
  0%, 100% { transform: translateX(-50%) translateY(0); }
  50% { transform: translateX(-50%) translateY(8px); }
}

/* ====== 3. Pain / Value ====== */
.pain-section { padding: 80px 0; background: var(--color-bg-light); }
.pain-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 32px; }
.pain-card {
  background: #fff; border-radius: var(--radius-lg); padding: 36px;
  box-shadow: 0 2px 12px rgba(0,0,0,0.04);
}
.pain-problems .section-label { color: var(--color-red); }
.pain-solution .section-label { color: var(--color-green); }
.pain-card li {
  padding: 10px 0; font-size: 15px; color: var(--color-text);
  border-bottom: 1px solid var(--color-border);
  display: flex; align-items: center; gap: 10px;
}
.pain-card li:last-child { border-bottom: none; }

/* ====== 4. Features ====== */
.features-section { padding: 80px 0; }
.features-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px; }
.feature-card {
  background: #fff; border: 1px solid var(--color-border);
  border-radius: var(--radius-lg); padding: 32px 24px; text-align: center;
  transition: transform 0.2s, box-shadow 0.2s;
}
.feature-card:hover { transform: translateY(-4px); box-shadow: 0 8px 30px rgba(0,0,0,0.08); }
.feature-icon { margin-bottom: 16px; display: flex; justify-content: center; }
.feature-card h3 { font-size: 18px; font-weight: 700; margin-bottom: 8px; color: var(--color-primary); }
.feature-card p { font-size: 14px; color: var(--color-text-muted); line-height: 1.7; }

/* ====== 5. How it works ====== */
.how-section { padding: 80px 0; background: var(--color-bg-dark); color: #fff; }
.how-section .section-title { color: #fff; }
.how-steps { display: flex; align-items: flex-start; justify-content: center; gap: 20px; margin-top: 40px; }
.how-step { text-align: center; flex: 1; max-width: 240px; }
.step-number {
  width: 40px; height: 40px; border-radius: 50%;
  background: linear-gradient(135deg, #22c55e, #16a34a);
  color: #fff; font-size: 20px; font-weight: 800;
  display: flex; align-items: center; justify-content: center; margin: 0 auto 12px;
}
.step-icon { font-size: 40px; margin-bottom: 12px; }
.how-step h3 { font-size: 18px; font-weight: 700; margin-bottom: 6px; }
.how-step p { font-size: 14px; color: #94a3b8; line-height: 1.6; }
.how-arrow { font-size: 28px; color: #475569; padding-top: 50px; flex-shrink: 0; }

/* ====== 6. Scenarios ====== */
.scenarios-section { padding: 80px 0; background: var(--color-bg-light); }
.scenarios-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 20px; }
.scenario-card {
  background: #fff; border-radius: var(--radius-lg); padding: 28px 20px;
  text-align: center; box-shadow: 0 2px 8px rgba(0,0,0,0.03); transition: transform 0.2s;
}
.scenario-card:hover { transform: translateY(-3px); }
.scenario-emoji { font-size: 44px; margin-bottom: 12px; }
.scenario-card h3 { font-size: 18px; font-weight: 700; margin-bottom: 8px; }
.scenario-card p { font-size: 13px; color: var(--color-text-muted); line-height: 1.6; margin-bottom: 14px; }
.scenario-tags { display: flex; flex-wrap: wrap; gap: 6px; justify-content: center; }
.scenario-tags span { font-size: 11px; padding: 3px 10px; border-radius: 10px; background: #f1f5f9; color: var(--color-text-muted); }

/* ====== 7. CTA ====== */
.cta-section { padding: 80px 0; }
.cta-card {
  display: flex; align-items: center; justify-content: center; gap: 48px;
  background: linear-gradient(135deg, #1e3a5f, #0f172a);
  border-radius: var(--radius-lg); padding: 48px; margin-top: 16px;
}
.qr-code {
  display: block; border-radius: var(--radius);
  background: #fff; padding: 6px;
}
.cta-info { color: #fff; }
.cta-main-text { font-size: 28px; font-weight: 700; margin-bottom: 8px; }
.cta-sub-text { font-size: 16px; color: #94a3b8; margin-bottom: 16px; }
.cta-sub-text strong { color: #fff; }
.cta-platform { font-size: 13px; color: #64748b; }

/* ====== 8. About ====== */
.about-section { padding: 80px 0; background: var(--color-bg-light); }
.about-cards { display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px; margin-top: 40px; }
.about-card {
  background: #fff; border-radius: var(--radius-lg); padding: 32px 24px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.03);
}
.about-card h3 { font-size: 17px; font-weight: 700; color: var(--color-primary); margin-bottom: 4px; }
.about-role { font-size: 13px; color: var(--color-green); font-weight: 600; margin-bottom: 12px; }
.about-card p:last-child { font-size: 14px; color: var(--color-text-muted); line-height: 1.7; }
.about-academic { text-align: center; margin-top: 32px; font-size: 14px; color: var(--color-text-muted); }

/* ====== 9. Footer ====== */
.footer { background: var(--color-bg-dark); color: #94a3b8; padding: 40px 0 24px; }
.footer-grid { display: flex; justify-content: space-between; align-items: flex-start; gap: 32px; margin-bottom: 24px; }
.footer-brand strong { display: block; font-size: 18px; color: #fff; margin-bottom: 4px; }
.footer-brand p { font-size: 13px; }
.footer-links { display: flex; gap: 20px; align-items: center; flex-wrap: wrap; }
.footer-links span { font-size: 13px; color: #64748b; }
.footer-links a { font-size: 13px; color: #94a3b8; transition: color 0.2s; }
.footer-links a:hover { color: #fff; }
.footer-bottom {
  border-top: 1px solid rgba(255,255,255,0.08); padding-top: 16px;
  display: flex; justify-content: space-between; font-size: 12px; flex-wrap: wrap; gap: 8px;
}
.footer-icp { color: #64748b; }

/* ====== Fade-in animation ====== */
.fade-in {
  opacity: 0; transform: translateY(24px);
  transition: opacity 0.6s ease-out, transform 0.6s ease-out;
}
.fade-in.visible { opacity: 1; transform: translateY(0); }

/* ====== Responsive ====== */
@media (max-width: 900px) {
  .hero-content { flex-direction: column; text-align: center; gap: 40px; }
  .hero-text h1 { font-size: 34px; }
  .hero-stats { justify-content: center; }
  .hero-actions { justify-content: center; }
  .hero-drone-svg { width: 240px; height: 260px; }
  .features-grid { grid-template-columns: repeat(2, 1fr); }
  .scenarios-grid { grid-template-columns: repeat(2, 1fr); }
  .about-cards { grid-template-columns: 1fr; }
  .pain-grid { grid-template-columns: 1fr; }
  .cta-card { flex-direction: column; text-align: center; }
  .how-steps { flex-direction: column; align-items: center; }
  .how-arrow { transform: rotate(90deg); padding-top: 0; }
  .nav-links, .nav-cta { display: none; }
  .nav-toggle { display: flex; }
  .nav.open .nav-links {
    display: flex; flex-direction: column;
    position: absolute; top: var(--nav-height); left: 0; right: 0;
    background: rgba(255,255,255,0.95); backdrop-filter: blur(12px);
    padding: 16px 24px; gap: 4px; border-bottom: 1px solid var(--color-border);
  }
  .nav.open .nav-links a { padding: 12px 16px; font-size: 16px; }
  .nav.open .nav-cta { display: block; margin: 8px 16px 16px; }
}

@media (max-width: 600px) {
  .section-title { font-size: 28px; }
  .hero-text h1 { font-size: 28px; }
  .hero-sub { font-size: 15px; }
  .features-grid { grid-template-columns: 1fr; }
  .scenarios-grid { grid-template-columns: 1fr; }
  .hero-stats { gap: 16px; }
  .stat strong { font-size: 22px; }
  .footer-grid { flex-direction: column; }
  .cta-card { padding: 32px 20px; }
  .pain-card { padding: 24px 20px; }
}