:root {
  /* Core SBT Colors */
  --sbt-bg: #f9f9f9;
  --sbt-surface: #ffffff;
  --sbt-text-primary: #111827;
  --sbt-text-secondary: #6b7280;
  --sbt-accent-orange: #ff5e1f;
  --sbt-accent-blue: #2974d1;
  --sbt-accent-gold: #debd17;
  --sbt-border: #e4e4e4;

  /* Spacing */
  --space-unit: 8px;
  --container-max-width: 1000px;
}

body {
  margin: 0;
  padding: 0;
  font-family: "Inter", "Noto Sans JP", "Helvetica Neue", Helvetica, Arial, sans-serif;
  background-color: var(--sbt-bg);
  color: var(--sbt-text-primary);
  line-height: 1.5; /* --lh-base from tokens.css */
  font-size: 15px; /* --fs-base from tokens.css */
}

:root:lang(ja) body {
  line-height: 1.8;
  letter-spacing: 0.03em;
  font-size: 13px;
}

.container {
  max-width: var(--container-max-width);
  margin: 0 auto;
  padding: 0 calc(var(--space-unit) * 3);
}

/* Hero Section */
.hero {
  padding: calc(var(--space-unit) * 12) 0;
  text-align: center;
  background: radial-gradient(circle at top, #ffffff 0%, #f9f9f9 100%);
}

.hero-ghost-container {
  display: flex;
  justify-content: center;
  gap: calc(var(--space-unit) * 4);
  margin-bottom: calc(var(--space-unit) * 6);
}

.hero-ghost {
  width: 120px;
  height: 120px;
  animation: float 3s ease-in-out infinite;
}

.hero-ghost--yellow { animation-delay: 0s; }
.hero-ghost--indigo { animation-delay: 0.5s; }
.hero-ghost--red { animation-delay: 1s; }

@keyframes float {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-15px); }
}

.hero-title {
  font-family: "Alike", serif;
  font-size: 3.5rem;
  font-weight: 700;
  margin: 0 0 calc(var(--space-unit) * 2);
  line-height: 1.1;
}

.hero-description {
  font-size: 1.25rem;
  color: var(--sbt-text-secondary);
  max-width: 700px;
  margin: 0 auto calc(var(--space-unit) * 6);
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  padding: calc(var(--space-unit) * 2) calc(var(--space-unit) * 4);
  border-radius: 999px;
  font-weight: 600;
  text-decoration: none;
  transition: transform 120ms ease, opacity 120ms ease;
}

.btn:hover {
  transform: scale(1.02);
  opacity: 0.9;
}

.btn-primary {
  background-color: var(--sbt-accent-blue);
  color: white;
}

/* Concept Cards */
.concept {
  padding: calc(var(--space-unit) * 10) 0;
}

.concept-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: calc(var(--space-unit) * 4);
}

.card {
  background: #f6f6f6; /* --answer-bg from tokens.css */
  padding: calc(var(--space-unit) * 5);
  border-radius: 20px;
  text-align: center;
  transition: transform 0.3s ease;
}

.card:hover {
  transform: translateY(-5px);
}

.card-icon {
  width: 80px;
  height: 80px;
  margin-bottom: calc(var(--space-unit) * 3);
}

.card-title {
  font-family: "Inter", "Noto Sans JP", sans-serif;
  font-size: 1.5rem;
  font-weight: 700;
  margin-bottom: calc(var(--space-unit) * 2);
}

.card-desc {
  color: var(--sbt-text-secondary);
  margin: 0;
}

/* Header */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(249, 249, 249, 0.92);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--sbt-border);
  transition: box-shadow 200ms ease;
}

.site-header.header--scrolled {
  box-shadow: 0 2px 12px rgba(0, 0, 0, 0.08);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding-top: 16px;
  padding-bottom: 16px;
  gap: 16px;
}

.header-logo {
  display: flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  color: inherit;
  flex-shrink: 0;
}

.header-logo__icon {
  width: 28px;
  height: 28px;
}

.header-logo__name {
  font-family: "Alike", serif;
  font-size: 1.25rem;
  font-weight: 700;
}

.header-nav {
  display: flex;
  align-items: center;
  gap: 20px;
}

.header-nav__link {
  text-decoration: none;
  color: var(--sbt-text-secondary);
  font-size: 0.9rem;
  transition: color 120ms ease;
}

.header-nav__link:hover {
  color: var(--sbt-text-primary);
}

/* Language Switcher */
.lang-switcher {
  display: flex;
  gap: 2px;
  background: var(--sbt-border);
  border-radius: 8px;
  padding: 3px;
}

.lang-switcher__btn {
  background: none;
  border: none;
  padding: 4px 8px;
  border-radius: 6px;
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--sbt-text-secondary);
  cursor: pointer;
  transition: background 120ms ease, color 120ms ease;
  letter-spacing: 0.05em;
}

.lang-switcher__btn:hover {
  color: var(--sbt-text-primary);
}

.lang-switcher__btn--active {
  background: white;
  color: var(--sbt-text-primary);
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
}

/* Hero CTA */
.btn-hero {
  padding: 14px 44px;
  font-size: 1.1rem;
}

/* Section Labels & Titles */
.section-label {
  text-align: center;
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--sbt-accent-blue);
  margin: 0 0 12px;
}

.section-title {
  text-align: center;
  font-family: "Alike", serif;
  font-size: 2.2rem;
  font-weight: 700;
  margin: 0 0 calc(var(--space-unit) * 6);
}

/* Problem Section */
.problem {
  padding: calc(var(--space-unit) * 10) 0;
  background-color: var(--sbt-text-primary);
  color: white;
}

.problem .section-label {
  color: rgba(255, 255, 255, 0.5);
}

.problem .section-title {
  color: white;
}

.problem-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: calc(var(--space-unit) * 3);
}

.problem-card {
  padding: calc(var(--space-unit) * 4);
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: 16px;
  background: rgba(255, 255, 255, 0.05);
}

.problem-card__title {
  font-size: 1.1rem;
  font-weight: 700;
  margin: 0 0 calc(var(--space-unit) * 1.5);
  color: white;
}

.problem-card__desc {
  color: rgba(255, 255, 255, 0.6);
  margin: 0;
  font-size: 0.95rem;
  line-height: 1.7;
}

/* How It Works Section */
.how-it-works {
  padding: calc(var(--space-unit) * 12) 0;
  background-color: var(--sbt-surface);
}

.flow-subtitle {
  text-align: center;
  font-family: "Alike", serif;
  font-size: 1.1rem;
  color: var(--sbt-text-secondary);
  margin: -20px 0 calc(var(--space-unit) * 8);
  letter-spacing: 0.05em;
}

.flow {
  display: flex;
  align-items: flex-start;
  gap: 0;
  overflow-x: auto;
  padding-bottom: 8px;
}

.flow-step {
  flex: 1;
  min-width: 180px;
  text-align: center;
  padding: 0 calc(var(--space-unit) * 2);
}

.flow-step__icon {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 80px;
  margin-bottom: calc(var(--space-unit) * 3);
}

/* Phone Mockup */
.phone-mockup {
  width: 160px;
  margin: 0 auto calc(var(--space-unit) * 3);
  border-radius: 28px;
  border: 8px solid #1a1a1a;
  outline: 1px solid #444;
  box-shadow: 0 24px 48px rgba(0, 0, 0, 0.25);
  overflow: hidden;
  background: #1a1a1a;
}

.phone-screen {
  width: 100%;
  height: auto;
  display: block;
}

.flow-step__title {
  font-size: 1rem;
  font-weight: 700;
  margin: 0 0 calc(var(--space-unit) * 1.5);
}

.flow-step__desc {
  font-size: 0.875rem;
  color: var(--sbt-text-secondary);
  margin: 0;
  line-height: 1.6;
}

.flow-arrow {
  flex-shrink: 0;
  font-size: 1.5rem;
  color: var(--sbt-accent-blue);
  padding: 24px 4px 0;
  opacity: 0.5;
  align-self: flex-start;
}


/* Final CTA Section */
.final-cta {
  padding: calc(var(--space-unit) * 14) 0;
  text-align: center;
}

.final-cta__title {
  font-family: "Alike", serif;
  font-size: 2.2rem;
  margin: 0 0 calc(var(--space-unit) * 2);
}

.final-cta__desc {
  color: var(--sbt-text-secondary);
  font-size: 1.1rem;
  margin: 0 0 calc(var(--space-unit) * 5);
}

/* Footer */
.site-footer {
  border-top: 1px solid var(--sbt-border);
  padding: calc(var(--space-unit) * 5) 0;
}

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

.footer-link {
  text-decoration: none;
  color: var(--sbt-text-secondary);
  font-size: 0.875rem;
  transition: color 120ms ease;
}

.footer-link:hover {
  color: var(--sbt-text-primary);
}

.footer-copy {
  color: var(--sbt-text-secondary);
  font-size: 0.875rem;
  margin: 0;
}

/* Responsive */
@media (max-width: 640px) {
  .hero-title {
    font-size: 2.4rem;
  }

  .section-title {
    font-size: 1.8rem;
  }

  .final-cta__title {
    font-size: 1.8rem;
  }

  .header-nav__link {
    display: none;
  }

  .flow {
    flex-direction: column;
    align-items: center;
  }

  .flow-arrow {
    transform: rotate(90deg);
    padding: 0;
    margin: 4px 0;
  }

  .flow-step {
    width: 100%;
    max-width: 280px;
  }

  .footer-inner {
    flex-direction: column;
    text-align: center;
  }
}