:root {
  --primary: #0f766e;
  --primary-light: #14b8a6;
  --primary-dark: #115e59;
  --accent: #0284c7;
  --accent-light: #e0f2fe;
  --bg-main: #f8fafc;
  --bg-card: #ffffff;
  --text-main: #0f172a;
  --text-muted: #475569;
  --text-light: #64748b;
  --border: #e2e8f0;
  --border-subtle: #f1f5f9;
  --gradient-hero: linear-gradient(135deg, #042f2e 0%, #115e59 50%, #0f766e 100%);
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.07), 0 2px 4px -2px rgb(0 0 0 / 0.05);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.08), 0 4px 6px -4px rgb(0 0 0 / 0.04);
  --radius-sm: 8px;
  --radius-md: 14px;
  --radius-lg: 20px;
  --transition: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

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

body {
  font-family: 'Noto Sans JP', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  color: var(--text-main);
  background-color: var(--bg-main);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

/* Container */
.container {
  width: 100%;
  max-width: 1140px;
  margin: 0 auto;
  padding: 0 24px;
}

/* Navigation */
.navbar {
  position: sticky;
  top: 0;
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
  z-index: 100;
  transition: var(--transition);
}

.nav-container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 700;
  font-size: 1.25rem;
  color: var(--primary-dark);
  text-decoration: none;
}

.brand-badge {
  background: var(--primary-light);
  color: white;
  font-size: 0.75rem;
  padding: 2px 8px;
  border-radius: 9999px;
  font-weight: 600;
}

.nav-links {
  display: flex;
  gap: 20px;
  list-style: none;
}

.nav-links a {
  text-decoration: none;
  color: var(--text-muted);
  font-size: 0.95rem;
  font-weight: 500;
  transition: var(--transition);
  padding: 6px 12px;
  border-radius: var(--radius-sm);
}

.nav-links a:hover {
  color: var(--primary);
  background-color: var(--bg-main);
}

/* Hero Section */
.hero {
  background: var(--gradient-hero);
  color: white;
  padding: 80px 0 70px;
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: "";
  position: absolute;
  top: -50%;
  right: -20%;
  width: 600px;
  height: 600px;
  background: radial-gradient(circle, rgba(20, 184, 166, 0.25) 0%, rgba(20, 184, 166, 0) 70%);
  border-radius: 50%;
  pointer-events: none;
}

.hero-content {
  position: relative;
  z-index: 2;
  max-width: 800px;
}

.hero-tag {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: rgba(255, 255, 255, 0.15);
  backdrop-filter: blur(8px);
  padding: 6px 16px;
  border-radius: 9999px;
  font-size: 0.85rem;
  letter-spacing: 0.05em;
  margin-bottom: 20px;
  border: 1px solid rgba(255, 255, 255, 0.2);
}

.hero-title {
  font-size: clamp(2.2rem, 5vw, 3.4rem);
  font-weight: 800;
  line-height: 1.2;
  margin-bottom: 20px;
  letter-spacing: -0.02em;
}

.hero-formula {
  display: inline-block;
  background: rgba(255, 255, 255, 0.15);
  padding: 0 12px;
  border-radius: var(--radius-sm);
  margin-left: 8px;
  font-family: 'Inter', sans-serif;
  color: #a7f3d0;
}

.hero-subtitle {
  font-size: 1.15rem;
  line-height: 1.8;
  color: #e2e8f0;
  margin-bottom: 36px;
}

.hero-stats {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 16px;
  margin-top: 30px;
}

.stat-box {
  background: rgba(255, 255, 255, 0.1);
  backdrop-filter: blur(10px);
  border: 1px solid rgba(255, 255, 255, 0.15);
  padding: 16px 20px;
  border-radius: var(--radius-md);
}

.stat-label {
  font-size: 0.8rem;
  color: #94a3b8;
  margin-bottom: 4px;
}

.stat-value {
  font-size: 1.35rem;
  font-weight: 700;
  color: #ffffff;
}

/* Sections Common */
.section {
  padding: 70px 0;
}

.section-alt {
  background-color: #f1f5f9;
}

.section-header {
  text-align: center;
  max-width: 680px;
  margin: 0 auto 48px;
}

.section-badge {
  display: inline-block;
  background-color: var(--accent-light);
  color: var(--accent);
  font-weight: 700;
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  padding: 4px 12px;
  border-radius: 9999px;
  margin-bottom: 12px;
}

.section-title {
  font-size: clamp(1.6rem, 3vw, 2.2rem);
  color: var(--text-main);
  margin-bottom: 12px;
  font-weight: 800;
}

.section-desc {
  color: var(--text-muted);
  font-size: 1rem;
}

/* Cards Grid */
.cards-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 24px;
}

.card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 28px;
  box-shadow: var(--shadow-sm);
  transition: var(--transition);
  display: flex;
  flex-direction: column;
}

.card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: #cbd5e1;
}

.card-icon {
  width: 52px;
  height: 52px;
  border-radius: var(--radius-sm);
  background: #f0fdfa;
  color: var(--primary);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.6rem;
  margin-bottom: 20px;
}

.card-title {
  font-size: 1.25rem;
  font-weight: 700;
  margin-bottom: 12px;
  color: var(--text-main);
}

.card-text {
  color: var(--text-muted);
  font-size: 0.95rem;
  line-height: 1.7;
}

/* State Change Interactive Cards */
.states-container {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 20px;
  margin-top: 20px;
}

.state-card {
  background: var(--bg-card);
  border: 2px solid var(--border);
  border-radius: var(--radius-md);
  padding: 24px;
  position: relative;
  transition: var(--transition);
}

.state-card.highlight {
  border-color: var(--primary);
}

.state-badge {
  display: inline-block;
  padding: 2px 10px;
  border-radius: 4px;
  font-size: 0.75rem;
  font-weight: 700;
  margin-bottom: 12px;
}

.state-gas { background: #e0f2fe; color: #0284c7; }
.state-solid { background: #f1f5f9; color: #475569; }
.state-liquid { background: #ecfdf5; color: #059669; }
.state-solution { background: #fef3c7; color: #d97706; }

.state-name {
  font-size: 1.2rem;
  font-weight: 700;
  margin-bottom: 8px;
}

.state-desc {
  font-size: 0.9rem;
  color: var(--text-muted);
}

/* Feature Spotlight Banner */
.spotlight-box {
  background: linear-gradient(135deg, #f0fdfa 0%, #e0f2fe 100%);
  border: 1px solid #ccfbf1;
  border-radius: var(--radius-lg);
  padding: 36px;
  margin-top: 40px;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 32px;
  align-items: center;
}

@media (max-width: 768px) {
  .spotlight-box {
    grid-template-columns: 1fr;
    padding: 24px;
  }
}

.spotlight-content h3 {
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--primary-dark);
  margin-bottom: 12px;
}

.cylinder-visual {
  background: white;
  border-radius: var(--radius-md);
  padding: 24px;
  box-shadow: var(--shadow-md);
  display: flex;
  align-items: center;
  gap: 20px;
}

.cylinder-icon {
  width: 60px;
  height: 100px;
  background: #10b981;
  border-radius: 12px 12px 6px 6px;
  position: relative;
  flex-shrink: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  font-weight: 800;
  font-size: 0.8rem;
  box-shadow: inset 0 0 10px rgba(0,0,0,0.2);
}

.cylinder-icon::before {
  content: "";
  position: absolute;
  top: -10px;
  width: 24px;
  height: 10px;
  background: #64748b;
  border-radius: 4px 4px 0 0;
}

/* Table / Specs styling */
.specs-table-wrapper {
  background: white;
  border-radius: var(--radius-md);
  border: 1px solid var(--border);
  overflow: hidden;
  box-shadow: var(--shadow-sm);
}

.specs-table {
  width: 100%;
  border-collapse: collapse;
  text-align: left;
}

.specs-table th, .specs-table td {
  padding: 16px 20px;
  border-bottom: 1px solid var(--border);
}

.specs-table th {
  background-color: #f8fafc;
  font-weight: 600;
  color: var(--text-main);
  width: 30%;
}

.specs-table td {
  color: var(--text-muted);
}

.specs-table tr:last-child th,
.specs-table tr:last-child td {
  border-bottom: none;
}

/* Footer */
.footer {
  background-color: #0f172a;
  color: #94a3b8;
  padding: 50px 0 30px;
  font-size: 0.9rem;
}

.footer-inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 20px;
  padding-bottom: 30px;
  border-bottom: 1px solid #334155;
}

.footer-brand {
  color: white;
  font-weight: 700;
  font-size: 1.1rem;
}

.copyright {
  text-align: center;
  padding-top: 24px;
  font-size: 0.85rem;
  color: #64748b;
}

/* Responsive */
@media (max-width: 640px) {
  .nav-links {
    display: none;
  }
  .hero {
    padding: 50px 0;
  }
  .section {
    padding: 48px 0;
  }
}