/* ============================================================
   kinaite — Landing Page Stylesheet v0
   White BG, cyan #29B6F6 accent, modern sans-serif
   ============================================================ */

/* ---------- Custom Properties ---------- */
:root {
  --bg: #FFFFFF;
  --bg-section: #F7FBFF;
  --bg-card: #FFFFFF;
  --text: #111827;
  --text-secondary: #4B5563;
  --text-muted: #9CA3AF;
  --accent: #29B6F6;
  --accent-dark: #0288D1;
  --accent-light: #E1F5FE;
  --border: #E5E7EB;
  --border-accent: #29B6F6;
  --layer-dot: #29B6F6;
}

/* ---------- Reset + Base ---------- */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
}

body {
  background-color: var(--bg);
  color: var(--text);
  font-family: 'Inter', 'PingFang SC', 'PingFang TC', 'Noto Sans SC', sans-serif;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

::selection {
  background-color: var(--accent);
  color: #ffffff;
}

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

/* ---------- Container ---------- */
.container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 32px;
}

/* ---------- Nav ---------- */
nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: 60px;
  background-color: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
  z-index: 100;
}

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

.nav-logo {
  font-size: 17px;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--text);
}

.nav-logo span {
  color: var(--accent);
}

/* ---------- Language Switcher ---------- */
.lang-switcher {
  display: flex;
  gap: 4px;
}

.lang-btn {
  background: none;
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 4px 10px;
  font-size: 12px;
  font-weight: 500;
  color: var(--text-muted);
  cursor: pointer;
  transition: all 0.15s ease;
  font-family: inherit;
}

.lang-btn:hover {
  border-color: var(--accent);
  color: var(--accent);
}

.lang-btn.active {
  background: var(--accent);
  border-color: var(--accent);
  color: #ffffff;
}

/* ---------- Hero ---------- */
.hero {
  padding: 140px 0 100px;
  text-align: center;
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  top: -120px;
  left: 50%;
  transform: translateX(-50%);
  width: 600px;
  height: 600px;
  background: radial-gradient(circle, rgba(41, 182, 246, 0.10) 0%, transparent 70%);
  pointer-events: none;
}

.hero-eyebrow {
  display: inline-block;
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
  background: var(--accent-light);
  border: 1px solid rgba(41, 182, 246, 0.3);
  border-radius: 100px;
  padding: 5px 14px;
  margin-bottom: 28px;
}

.hero-title {
  font-size: clamp(36px, 6vw, 64px);
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.1;
  color: var(--text);
  margin-bottom: 24px;
}

.hero-cursor {
  color: var(--accent);
  animation: blink 1.06s step-end infinite;
}

@keyframes blink {
  0%, 100% { opacity: 1; }
  50% { opacity: 0; }
}

.hero-sub {
  font-size: clamp(16px, 2vw, 19px);
  color: var(--text-secondary);
  max-width: 640px;
  margin: 0 auto 48px;
  line-height: 1.6;
}

.hero-cta {
  display: inline-block;
  background: var(--accent);
  color: #ffffff;
  font-size: 14px;
  font-weight: 600;
  padding: 14px 32px;
  border-radius: 8px;
  transition: background 0.15s ease, transform 0.15s ease;
  letter-spacing: 0.01em;
}

.hero-cta:hover {
  background: var(--accent-dark);
  transform: translateY(-1px);
}

/* ---------- Stack Section ---------- */
.stack {
  padding: 96px 0;
  background: var(--bg-section);
}

.section-label {
  display: block;
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 48px;
}

.stack-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 24px;
}

@media (max-width: 680px) {
  .stack-grid {
    grid-template-columns: 1fr;
  }
}

.layer-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 28px 28px 28px 24px;
  position: relative;
  transition: box-shadow 0.2s ease, border-color 0.2s ease;
}

.layer-card:hover {
  border-color: var(--border-accent);
  box-shadow: 0 4px 24px rgba(41, 182, 246, 0.10);
}

.layer-tag {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 12px;
}

.layer-dot {
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background: var(--accent);
  flex-shrink: 0;
}

.layer-heading {
  font-size: 18px;
  font-weight: 700;
  letter-spacing: -0.01em;
  color: var(--text);
  margin-bottom: 10px;
  line-height: 1.3;
}

.layer-body {
  font-size: 14px;
  color: var(--text-secondary);
  line-height: 1.65;
}

/* ---------- Thesis Strip ---------- */
.thesis {
  padding: 80px 0;
}

.thesis .container {
  text-align: center;
}

.thesis-rule {
  width: 48px;
  height: 2px;
  background: var(--accent);
  margin: 0 auto 40px;
  border: none;
  transform: scaleX(0);
  transition: transform 0.6s ease;
}

.thesis-rule.visible {
  transform: scaleX(1);
}

.thesis-heading {
  font-size: clamp(22px, 3vw, 32px);
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--text);
  margin-bottom: 16px;
  max-width: 640px;
  margin-left: auto;
  margin-right: auto;
}

.thesis-body {
  font-size: 16px;
  color: var(--text-secondary);
  max-width: 580px;
  margin: 0 auto;
  line-height: 1.7;
}

/* ---------- Footer ---------- */
.footer {
  background: var(--text);
  color: rgba(255, 255, 255, 0.65);
  padding: 48px 0 32px;
}

.footer-top {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 16px;
  margin-bottom: 32px;
}

.footer-logo {
  font-size: 16px;
  font-weight: 700;
  color: #ffffff;
  letter-spacing: -0.01em;
}

.footer-parent-link {
  font-size: 13px;
  color: rgba(255,255,255,0.5);
  transition: color 0.15s ease;
}

.footer-parent-link:hover {
  color: var(--accent);
}

.footer-bottom {
  border-top: 1px solid rgba(255, 255, 255, 0.1);
  padding-top: 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 8px;
}

.footer-copy {
  font-size: 12px;
  color: rgba(255, 255, 255, 0.35);
}

/* ---------- Fade-in ---------- */
.fade-in {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.55s ease, transform 0.55s ease;
}

.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ---------- Responsive ---------- */
@media (max-width: 768px) {
  .container {
    padding: 0 20px;
  }

  .hero {
    padding: 110px 0 72px;
  }

  .footer-top {
    flex-direction: column;
    align-items: flex-start;
  }
}