:root[data-theme='light'] {
  --primary: #3b82f6;
  --primary-dark: #1d4ed8;
  --accent: #00d4aa;
  --bg-1: #ffffff;
  --bg-2: #f8fafc;
  --text-1: #0f172a;
  --text-2: #475569;
  --border: #e2e8f0;
  --soft-accent: #dbeafe;
}

:root[data-theme='dark'] {
  --primary: #60a5fa;
  --primary-dark: #3b82f6;
  --accent: #00d4aa;
  --bg-1: #020617;
  --bg-2: #0f172a;
  --text-1: #f8fafc;
  --text-2: #94a3b8;
  --border: #1e293b;
  --soft-accent: #1e3a8a;
}

* { box-sizing: border-box; }

body.intro-body {
  margin: 0;
  font-family: 'Pretendard', 'Pretendard Variable', -apple-system, BlinkMacSystemFont, sans-serif;
  background-color: var(--bg-1);
  color: var(--text-1);
  line-height: 1.6;
  transition: background-color 0.3s, color 0.3s;
}

.container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 2rem;
}

/* ========== Top Navigation ========== */
.intro-nav {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(255, 255, 255, 0.85);
  border-bottom: 1px solid var(--border);
  backdrop-filter: saturate(180%) blur(12px);
  -webkit-backdrop-filter: saturate(180%) blur(12px);
}
:root[data-theme='dark'] .intro-nav { background: rgba(2, 6, 23, 0.78); }
.intro-nav__inner {
  max-width: 1180px;
  margin: 0 auto;
  padding: 0.85rem 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1.5rem;
}
.intro-nav__brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 1.05rem;
  font-weight: 800;
  color: var(--text-1);
  text-decoration: none;
}
.intro-nav__logo {
  width: 32px; height: 32px; border-radius: 9px;
  background: linear-gradient(135deg, var(--primary), var(--accent));
  color: white;
  display: grid; place-items: center;
}
.intro-nav__links {
  display: none;
  gap: 1.4rem;
  font-size: 0.85rem;
}
.intro-nav__links a {
  color: var(--text-2);
  text-decoration: none;
  font-weight: 500;
  transition: color 0.15s;
}
.intro-nav__links a:hover { color: var(--text-1); }
.intro-nav__actions { display: flex; align-items: center; gap: 12px; }
.intro-nav__cta {
  padding: 8px 16px;
  background: var(--primary);
  color: white;
  border-radius: 8px;
  font-size: 0.85rem;
  font-weight: 600;
  text-decoration: none;
  transition: background 0.15s;
}
.intro-nav__cta:hover { background: var(--primary-dark); }
@media (min-width: 900px) { .intro-nav__links { display: flex; } }

/* Tier badge in nav */
.tier-badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 5px 10px;
  border-radius: 999px;
  background: rgba(245, 158, 11, 0.12);
  color: #b45309;
  border: 1px solid rgba(245, 158, 11, 0.4);
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.05em;
  text-decoration: none;
}
.tier-badge__dot {
  width: 6px; height: 6px; border-radius: 999px; background: #f59e0b;
  animation: tier-pulse 1.6s ease-in-out infinite;
}
.tier-pill {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 5px 10px;
  border-radius: 999px;
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.05em;
}
.tier-pill__dot {
  width: 6px; height: 6px; border-radius: 999px;
  animation: tier-pulse 1.6s ease-in-out infinite;
}
.tier-pill--amber { background: rgba(245,158,11,0.12); color: #b45309; border:1px solid rgba(245,158,11,0.4); }
.tier-pill--amber .tier-pill__dot { background: #f59e0b; }
.tier-pill--blue { background: rgba(59,130,246,0.12); color: #1d4ed8; border:1px solid rgba(59,130,246,0.4); }
.tier-pill--blue .tier-pill__dot { background: #3b82f6; }
.tier-pill--emerald { background: rgba(16,185,129,0.12); color: #047857; border:1px solid rgba(16,185,129,0.4); }
.tier-pill--emerald .tier-pill__dot { background: #10b981; }
@keyframes tier-pulse {
  0%, 100% { opacity: 1; transform: scale(1); }
  50% { opacity: 0.55; transform: scale(0.85); }
}

/* ========== Sections ========== */
.section { padding: 5.5rem 0; }
.section.hero { padding: 6.5rem 0 5.5rem; text-align: center; }
.section.dark-alt { background-color: var(--bg-2); }
.section.accent-bg {
  background: linear-gradient(135deg, var(--primary), var(--primary-dark));
  color: white;
}
.section.accent-bg .section-title,
.section.accent-bg p { color: white; }

.section-eyebrow {
  display: inline-block;
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--primary);
  margin-bottom: 0.85rem;
}
.section-eyebrow.centered { display: block; text-align: center; }
.section-title {
  font-size: 2.4rem;
  font-weight: 800;
  letter-spacing: -0.02em;
  line-height: 1.2;
  margin: 0 0 1rem;
}
.section-title.centered { text-align: center; }
.section-desc {
  font-size: 1.05rem;
  color: var(--text-2);
  margin: 0 0 1rem;
}
.section-desc.centered { text-align: center; max-width: 680px; margin: 0 auto 1rem; }

/* ========== Hero ========== */
.hero-eyebrow {
  display: inline-block;
  padding: 6px 14px;
  border-radius: 999px;
  background: var(--soft-accent);
  color: var(--primary-dark);
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.05em;
  margin-bottom: 1.5rem;
}
.hero-title {
  font-size: 4.2rem;
  font-weight: 900;
  letter-spacing: -0.025em;
  line-height: 1.05;
  margin: 0 0 1.5rem;
}
.highlight {
  background: linear-gradient(135deg, var(--primary), var(--accent));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.hero-subtitle {
  font-size: 1.25rem;
  color: var(--text-2);
  max-width: 700px;
  margin: 0 auto 2.5rem;
}
.hero-stats {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 1.5rem;
  max-width: 760px;
  margin: 4rem auto 0;
  padding-top: 2.5rem;
  border-top: 1px dashed var(--border);
}
.hero-stat { text-align: center; }
.hero-stat__num {
  display: block;
  font-size: 2.2rem;
  font-weight: 800;
  color: var(--primary-dark);
  line-height: 1;
}
.hero-stat__unit { font-size: 1rem; color: var(--text-2); margin-left: 4px; font-weight: 600; }
.hero-stat__label { display: block; margin-top: 8px; font-size: 0.8rem; color: var(--text-2); }

/* ========== Grids ========== */
.grid-2 {
  display: grid;
  grid-template-columns: 1fr;
  gap: 3rem;
  align-items: center;
}
@media (min-width: 800px) { .grid-2 { grid-template-columns: 1fr 1fr; gap: 4rem; } }

/* ========== Comparison Box ========== */
.comparison-box {
  background: var(--bg-1);
  border: 1px solid var(--border);
  border-radius: 18px;
  overflow: hidden;
  box-shadow: 0 6px 24px rgba(15, 23, 42, 0.06);
}
.vs-item { padding: 1.5rem; }
.vs-item.active { background: var(--soft-accent); color: var(--text-1); }
.vs-label {
  font-weight: 700;
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  display: block;
  margin-bottom: 0.5rem;
  color: var(--primary-dark);
}
.vs-divider {
  text-align: center;
  background: #e2e8f0;
  font-size: 0.7rem;
  font-weight: 700;
  color: #64748b;
  padding: 0.3rem;
  letter-spacing: 0.1em;
}
:root[data-theme='dark'] .vs-divider { background: var(--bg-2); color: var(--text-2); }

.problem-list {
  margin: 1.5rem 0 0;
  padding: 0;
  list-style: none;
}
.problem-list li {
  padding: 8px 0 8px 22px;
  position: relative;
  font-size: 0.92rem;
  color: var(--text-2);
}
.problem-list li::before {
  content: "✕";
  position: absolute;
  left: 0;
  top: 8px;
  color: #ef4444;
  font-weight: 700;
}

/* ========== Engine Cards ========== */
.features-grid-v2 {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1.5rem;
  margin-top: 3rem;
}
@media (min-width: 900px) { .features-grid-v2 { grid-template-columns: repeat(3, 1fr); gap: 2rem; } }

.engine-card {
  padding: 2.2rem;
  background: var(--bg-2);
  border: 1px solid var(--border);
  border-radius: 22px;
  position: relative;
  transition: transform 0.2s, box-shadow 0.2s;
}
.engine-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 18px 40px rgba(15, 23, 42, 0.08);
}
.engine-num {
  font-size: 2.5rem;
  font-weight: 900;
  background: linear-gradient(135deg, var(--primary), var(--accent));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  opacity: 0.45;
  position: absolute;
  top: 1rem;
  right: 1.5rem;
}
.engine-card h3 {
  font-size: 1.15rem;
  margin: 0 0 0.75rem;
  color: var(--text-1);
}
.engine-card > p {
  margin: 0 0 1rem;
  color: var(--text-2);
  font-size: 0.92rem;
}
.engine-points {
  margin: 0;
  padding: 0;
  list-style: none;
  border-top: 1px dashed var(--border);
  padding-top: 1rem;
}
.engine-points li {
  font-size: 0.83rem;
  padding: 4px 0 4px 22px;
  position: relative;
  color: var(--text-2);
}
.engine-points li::before {
  content: "✓";
  position: absolute;
  left: 0;
  top: 4px;
  color: var(--accent);
  font-weight: 700;
}

/* ========== Stats ========== */
.stats-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 2rem;
  margin-top: 3rem;
}
@media (min-width: 800px) { .stats-grid { grid-template-columns: repeat(4, 1fr); } }
.stat-item p { font-size: 0.85rem; opacity: 0.85; margin-top: 6px; }
.stat-val {
  font-size: 2.6rem;
  font-weight: 900;
  display: block;
  line-height: 1;
}

/* ========== Personas ========== */
.persona-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1.2rem;
  margin-top: 2.5rem;
}
@media (min-width: 700px) { .persona-grid { grid-template-columns: repeat(2, 1fr); } }
@media (min-width: 1000px) { .persona-grid { grid-template-columns: repeat(4, 1fr); } }
.persona-card {
  padding: 1.5rem;
  background: var(--bg-2);
  border: 1px solid var(--border);
  border-radius: 16px;
  transition: transform 0.2s;
}
.persona-card:hover { transform: translateY(-2px); }
.persona-icon {
  width: 40px; height: 40px;
  border-radius: 12px;
  display: grid; place-items: center;
  font-weight: 800;
  font-size: 1.1rem;
  margin-bottom: 0.75rem;
}
.persona-card h3 { margin: 0 0 4px; font-size: 1.05rem; }
.persona-role {
  margin: 0 0 0.75rem;
  font-size: 0.75rem;
  color: var(--text-2);
  font-weight: 600;
  letter-spacing: 0.04em;
}
.persona-task {
  margin: 0;
  font-size: 0.85rem;
  color: var(--text-2);
  line-height: 1.55;
}

/* ========== Tier Grid ========== */
.tier-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1.2rem;
  margin-top: 2.5rem;
}
@media (min-width: 800px) { .tier-grid { grid-template-columns: repeat(3, 1fr); } }
.tier-item {
  padding: 1.75rem;
  background: var(--bg-1);
  border: 1px solid var(--border);
  border-radius: 18px;
}
.tier-item h4 {
  margin: 0 0 0.5rem;
  font-size: 1.1rem;
  color: var(--text-1);
}
.tier-stack {
  margin: 0 0 0.5rem;
  font-size: 0.85rem;
  color: var(--text-2);
  font-weight: 500;
}
.tier-use {
  margin: 0;
  font-size: 0.78rem;
  color: var(--text-2);
  opacity: 0.85;
}
.tier-item--pilot { border-left: 4px solid #f59e0b; }
.tier-item--preprod { border-left: 4px solid #3b82f6; }
.tier-item--prod { border-left: 4px solid #10b981; }

/* ========== Roadmap ========== */
.roadmap {
  margin: 3rem 0 0;
  padding: 0;
  list-style: none;
  display: grid;
  grid-template-columns: 1fr;
  gap: 12px;
  counter-reset: roadmap;
}
@media (min-width: 800px) { .roadmap { grid-template-columns: repeat(2, 1fr); } }
@media (min-width: 1100px) { .roadmap { grid-template-columns: repeat(3, 1fr); } }
.roadmap li {
  padding: 1rem 1.25rem;
  background: var(--bg-2);
  border: 1px solid var(--border);
  border-radius: 14px;
  display: flex;
  align-items: center;
  gap: 1rem;
}
.roadmap li strong {
  font-weight: 800;
  color: var(--primary-dark);
  font-size: 1.1rem;
  min-width: 40px;
}
.roadmap li span { font-size: 0.85rem; color: var(--text-2); line-height: 1.5; }

/* ========== Buttons ========== */
.cta-group { display: flex; gap: 1rem; justify-content: center; flex-wrap: wrap; }
.btn-primary {
  display: inline-block;
  background: var(--primary);
  color: white;
  padding: 1rem 2.2rem;
  border-radius: 50px;
  font-weight: 700;
  text-decoration: none;
  transition: transform 0.2s, box-shadow 0.2s, background 0.2s;
  box-shadow: 0 8px 24px rgba(59, 130, 246, 0.32);
}
.btn-primary:hover {
  transform: translateY(-2px);
  background: var(--primary-dark);
  box-shadow: 0 12px 32px rgba(59, 130, 246, 0.4);
}
.btn-secondary {
  display: inline-block;
  padding: 1rem 1.6rem;
  color: var(--text-1);
  text-decoration: none;
  font-weight: 700;
}

.centered { text-align: center; }

/* ========== Vision Badge ========== */
.vision-badge {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 2.5rem;
  background: rgba(255, 255, 255, 0.12);
  border: 1px solid rgba(255, 255, 255, 0.25);
  border-radius: 20px;
  color: white;
}

/* ========== Footer ========== */
.footer {
  padding: 3rem 0;
  border-top: 1px solid var(--border);
  font-size: 0.9rem;
  color: var(--text-2);
}
.footer-inner {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
  align-items: flex-start;
  justify-content: space-between;
}
@media (min-width: 700px) {
  .footer-inner { flex-direction: row; align-items: center; }
}
.footer-links { display: flex; gap: 1.5rem; flex-wrap: wrap; }
.footer-links a { color: var(--text-2); text-decoration: none; font-weight: 500; font-size: 0.85rem; }
.footer-links a:hover { color: var(--text-1); }

/* ========== Theme Switch ========== */
.theme-switch-btn {
  background: var(--bg-2);
  border: 1px solid var(--border);
  padding: 0.5rem 0.7rem;
  border-radius: 50%;
  cursor: pointer;
  font-size: 1rem;
  line-height: 1;
}

/* ========== Responsive ========== */
@media (max-width: 700px) {
  .section { padding: 4rem 0; }
  .section.hero { padding: 4rem 0; }
  .hero-title { font-size: 2.6rem; }
  .hero-subtitle { font-size: 1rem; }
  .section-title { font-size: 1.8rem; }
}