/* ==========================================================================
   Design System & Variable Declarations (Light / Dark Themes)
   ========================================================================== */
:root {
  /* Default: Dark Theme */
  --bg-gradient: linear-gradient(180deg, #0f172a 0%, #1e1b4b 100%);
  --bg-color: #0f172a;
  --card-bg: rgba(30, 41, 59, 0.75);
  --card-border: rgba(255, 255, 255, 0.08);
  --text-primary: #e2e8f0;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;
  --accent: #818cf8;
  --accent-bright: #6366f1;
  --accent-glow: rgba(99, 102, 241, 0.15);
  --header-bg: rgba(15, 23, 42, 0.8);
  --header-border: rgba(255, 255, 255, 0.05);
  --toc-active-bg: rgba(129, 140, 248, 0.1);
  --badge-local-bg: rgba(52, 211, 153, 0.1);
  --badge-local-text: #34d399;
  --badge-external-bg: rgba(251, 191, 36, 0.1);
  --badge-external-text: #fbbf24;
  --step-num-bg: rgba(99, 102, 241, 0.15);

  --transition-speed: 0.3s;
  --transition-bezier: cubic-bezier(0.4, 0, 0.2, 1);
  --glow-1-color: rgba(99, 102, 241, 0.15);
  --glow-2-color: rgba(139, 92, 246, 0.12);
}

[data-theme="light"] {
  --bg-gradient: linear-gradient(180deg, #f8fafc 0%, #eef2ff 100%);
  --bg-color: #f8fafc;
  --card-bg: rgba(255, 255, 255, 0.8);
  --card-border: rgba(99, 102, 241, 0.08);
  --text-primary: #1e293b;
  --text-secondary: #475569;
  --text-muted: #94a3b8;
  --accent: #6366f1;
  --accent-bright: #4f46e5;
  --accent-glow: rgba(99, 102, 241, 0.08);
  --header-bg: rgba(248, 250, 252, 0.8);
  --header-border: rgba(0, 0, 0, 0.05);
  --toc-active-bg: rgba(99, 102, 241, 0.08);
  --badge-local-bg: rgba(5, 150, 105, 0.08);
  --badge-local-text: #059669;
  --badge-external-bg: rgba(217, 119, 6, 0.08);
  --badge-external-text: #d97706;
  --step-num-bg: rgba(99, 102, 241, 0.08);

  --glow-1-color: rgba(99, 102, 241, 0.06);
  --glow-2-color: rgba(139, 92, 246, 0.05);
}

/* ==========================================================================
   Reset & Base Styles
   ========================================================================== */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  font-family: 'Inter', 'Noto Sans JP', 'Outfit', sans-serif;
  background-color: var(--bg-color);
  background-image: var(--bg-gradient);
  color: var(--text-primary);
  min-height: 100vh;
  position: relative;
  overflow-x: hidden;
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  transition: background-color var(--transition-speed) var(--transition-bezier),
    color var(--transition-speed) var(--transition-bezier);
}

/* ==========================================================================
   Background Glow Effects
   ========================================================================== */
.glow-bg {
  position: absolute;
  width: 50vw;
  height: 50vw;
  max-width: 600px;
  max-height: 600px;
  border-radius: 50%;
  filter: blur(100px);
  z-index: -1;
  pointer-events: none;
  opacity: 0.8;
  transition: filter var(--transition-speed) var(--transition-bezier);
}

.glow-bg-1 {
  top: -100px;
  right: -50px;
  background-color: var(--glow-1-color);
}

.glow-bg-2 {
  top: 600px;
  left: -100px;
  background-color: var(--glow-2-color);
}

/* ==========================================================================
   Header Component
   ========================================================================== */
#site-header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  z-index: 100;
  background-color: var(--header-bg);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--header-border);
  transition: background-color var(--transition-speed) var(--transition-bezier),
    border-color var(--transition-speed) var(--transition-bezier);
}

.header-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 1rem 2rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.logo {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  text-decoration: none;
  color: var(--text-primary);
  font-weight: 800;
  font-size: 1.25rem;
  font-family: 'Outfit', sans-serif;
  letter-spacing: -0.5px;
  transition: transform 0.2s ease;
}

.logo:hover {
  transform: scale(1.02);
}

.logo-icon {
  width: 36px;
  height: 36px;
  border-radius: 10px;
  background: linear-gradient(135deg, var(--accent-bright) 0%, var(--accent) 100%);
  color: white;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 4px 12px var(--accent-glow);
}

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

/* Theme Toggle Button */
.theme-btn {
  background: none;
  border: 1px solid var(--card-border);
  background-color: var(--card-bg);
  color: var(--text-primary);
  padding: 0.5rem;
  border-radius: 10px;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.2s ease;
}

.theme-btn:hover {
  background-color: var(--accent-glow);
  border-color: var(--accent);
  color: var(--accent);
  transform: translateY(-1px);
}

.theme-btn svg {
  transition: transform 0.4s cubic-bezier(0.34, 1.56, 0.64, 1);
}

.theme-btn:active svg {
  transform: scale(0.8) rotate(15deg);
}

/* Toggle icon display based on html data-theme */
[data-theme="dark"] .icon-sun {
  display: block;
}

[data-theme="dark"] .icon-moon {
  display: none;
}

[data-theme="light"] .icon-sun {
  display: none;
}

[data-theme="light"] .icon-moon {
  display: block;
}

/* ==========================================================================
   Hero Section
   ========================================================================== */
#hero {
  padding: 8rem 2rem 4rem;
  text-align: center;
  position: relative;
}

.hero-container {
  max-width: 800px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1.5rem;
}

.hero-badge {
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 2px;
  background-color: var(--accent-glow);
  color: var(--accent);
  padding: 0.35rem 1rem;
  border-radius: 100px;
  border: 1px solid rgba(99, 102, 241, 0.2);
  animation: fadeIn 0.8s ease;
}

.hero-title {
  font-family: 'Noto Sans JP', sans-serif;
  font-weight: 900;
  font-size: 2.75rem;
  letter-spacing: -1px;
  line-height: 1.25;
  background: linear-gradient(135deg, var(--text-primary) 30%, var(--accent) 100%);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  animation: slideUp 0.8s var(--transition-bezier);
}

.hero-subtitle {
  font-size: 1.125rem;
  color: var(--text-secondary);
  max-width: 600px;
  margin-bottom: 1.5rem;
  animation: slideUp 1s var(--transition-bezier);
}

.app-card {
  display: flex;
  align-items: center;
  text-align: left;
  gap: 1.5rem;
  background-color: var(--card-bg);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border: 1px solid var(--card-border);
  padding: 1.25rem 2rem;
  border-radius: 20px;
  max-width: 650px;
  width: 100%;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.05);
  animation: slideUp 1.2s var(--transition-bezier);
  transition: transform 0.3s ease, border-color 0.3s ease;
}

.app-card:hover {
  transform: translateY(-2px);
  border-color: rgba(99, 102, 241, 0.3);
}

.app-card-icon {
  width: 52px;
  height: 52px;
  border-radius: 14px;
  background: linear-gradient(135deg, var(--accent-bright) 0%, var(--accent) 100%);
  color: white;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  box-shadow: 0 6px 16px var(--accent-glow);
}

.app-card-icon svg {
  width: 28px;
  height: 28px;
}

.app-card-info h3 {
  font-size: 1.1rem;
  font-weight: 700;
  margin-bottom: 0.25rem;
  color: var(--text-primary);
}

.app-card-info p {
  font-size: 0.875rem;
  color: var(--text-secondary);
  line-height: 1.5;
}

/* ==========================================================================
   Main Content Layout
   ========================================================================== */
#main-content {
  padding: 0 2rem 6rem;
}

.main-container {
  max-width: 1100px;
  margin: 0 auto;
  display: grid;
  grid-template-columns: 260px 1fr;
  gap: 3rem;
  position: relative;
}

/* Sidebar Navigation */
.sidebar {
  position: sticky;
  top: 7rem;
  height: fit-content;
}

.toc {
  background-color: var(--card-bg);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border: 1px solid var(--card-border);
  padding: 1.5rem;
  border-radius: 20px;
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.02);
}

.toc ul {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
}

.toc-link {
  display: block;
  padding: 0.5rem 0.85rem;
  border-radius: 8px;
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 0.9rem;
  font-weight: 500;
  transition: all 0.25s ease;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.toc-link:hover {
  color: var(--accent);
  background-color: var(--toc-active-bg);
}

.toc-link.active {
  color: var(--accent);
  background-color: var(--toc-active-bg);
  font-weight: 700;
  border-left: 3px solid var(--accent);
  border-top-left-radius: 2px;
  border-bottom-left-radius: 2px;
  padding-left: 0.75rem;
  /* adjustment for border */
}

/* Content Body */
.content-body {
  display: flex;
  flex-direction: column;
  gap: 3.5rem;
}

/* Promise Banner Card */
.promise-card {
  display: flex;
  gap: 1.25rem;
  background-color: rgba(99, 102, 241, 0.07);
  border: 1px dashed rgba(99, 102, 241, 0.3);
  padding: 1.5rem;
  border-radius: 16px;
  align-items: flex-start;
}

.promise-icon {
  color: var(--accent);
  flex-shrink: 0;
  padding-top: 0.15rem;
}

.promise-text h4 {
  font-size: 1rem;
  font-weight: 700;
  margin-bottom: 0.35rem;
  color: var(--text-primary);
}

.promise-text p {
  font-size: 0.875rem;
  color: var(--text-secondary);
  line-height: 1.6;
}

/* Policy Sections */
.policy-section {
  scroll-margin-top: 7.5rem;
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.policy-section h2 {
  font-family: 'Noto Sans JP', sans-serif;
  font-size: 1.65rem;
  font-weight: 700;
  color: var(--text-primary);
  border-bottom: 2px solid var(--card-border);
  padding-bottom: 0.5rem;
  margin-bottom: 0.5rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.policy-section p {
  color: var(--text-secondary);
  font-size: 1rem;
}

.policy-section strong {
  color: var(--text-primary);
}

.policy-section ul {
  list-style-type: none;
  padding-left: 0.5rem;
}

.policy-section ul li {
  position: relative;
  padding-left: 1.5rem;
  margin-bottom: 0.5rem;
  color: var(--text-secondary);
}

.policy-section ul li::before {
  content: "•";
  color: var(--accent);
  font-weight: bold;
  font-size: 1.25rem;
  position: absolute;
  left: 0.25rem;
  top: -2px;
}

/* Data grid styling in Section 2 */
.data-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
  margin-top: 0.75rem;
}

.data-item {
  background-color: var(--card-bg);
  border: 1px solid var(--card-border);
  padding: 1.5rem;
  border-radius: 16px;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  transition: all 0.3s ease;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.01);
}

.data-item:hover {
  transform: translateY(-2px);
  border-color: rgba(99, 102, 241, 0.2);
  box-shadow: 0 8px 24px rgba(99, 102, 241, 0.04);
}

.data-item-header {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.data-item-header h5 {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--text-primary);
}

.data-badge {
  font-size: 0.7rem;
  font-weight: 700;
  padding: 0.2rem 0.6rem;
  border-radius: 100px;
  width: fit-content;
}

.data-badge.local {
  background-color: var(--badge-local-bg);
  color: var(--badge-local-text);
}

.data-badge.external {
  background-color: var(--badge-external-bg);
  color: var(--badge-external-text);
}

.data-item p {
  font-size: 0.875rem;
  line-height: 1.6;
}

/* Link Box Component */
.link-box {
  margin-top: 0.5rem;
}

.external-link {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  color: var(--accent);
  text-decoration: none;
  font-weight: 600;
  font-size: 0.95rem;
  transition: color 0.2s ease;
  padding: 0.5rem 0;
  border-bottom: 1px solid transparent;
}

.external-link:hover {
  color: var(--accent-bright);
  border-color: var(--accent-bright);
}

.external-link svg {
  width: 14px;
  height: 14px;
  transition: transform 0.2s ease;
}

.external-link:hover svg {
  transform: translate(2px, -2px);
}

/* Step Card Component (Section 6) */
.step-card {
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
  background-color: var(--card-bg);
  border: 1px solid var(--card-border);
  padding: 1.75rem;
  border-radius: 20px;
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.01);
}

.step-row {
  display: flex;
  gap: 1.25rem;
  align-items: flex-start;
}

.step-row:not(:last-child) {
  border-bottom: 1px solid var(--card-border);
  padding-bottom: 1.25rem;
}

.step-num {
  width: 32px;
  height: 32px;
  border-radius: 50%;
  background-color: var(--step-num-bg);
  color: var(--accent);
  font-weight: 700;
  font-size: 1rem;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.step-content h6 {
  font-size: 1rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 0.25rem;
}

.step-content p {
  font-size: 0.875rem;
  line-height: 1.6;
}

/* Contact Card (Section 9) */
.contact-card {
  display: flex;
  justify-content: space-between;
  align-items: center;
  background-color: var(--card-bg);
  border: 1px solid var(--card-border);
  padding: 1.5rem 2rem;
  border-radius: 20px;
  gap: 1.5rem;
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.02);
}

.contact-info {
  display: flex;
  align-items: center;
  gap: 1.25rem;
}

.contact-icon {
  width: 48px;
  height: 48px;
  border-radius: 12px;
  background-color: var(--accent-glow);
  color: var(--accent);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.contact-details {
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
}

.contact-details .label {
  font-size: 0.75rem;
  color: var(--text-muted);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.contact-details .value {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--text-primary);
  word-break: break-all;
  user-select: all;
}

.action-btn {
  background-color: var(--accent);
  color: var(--bg-color);
  border: none;
  font-weight: 700;
  font-size: 0.9rem;
  padding: 0.75rem 1.5rem;
  border-radius: 10px;
  cursor: pointer;
  transition: all 0.2s ease;
  flex-shrink: 0;
  box-shadow: 0 4px 12px var(--accent-glow);
  position: relative;
  overflow: hidden;
}

.action-btn:hover {
  background-color: var(--accent-bright);
  transform: translateY(-1px);
}

.action-btn:active {
  transform: translateY(1px);
}

.action-btn .btn-success-text {
  display: none;
}

/* State when email is copied successfully */
.action-btn.copied {
  background-color: var(--badge-local-text);
  color: white;
}

.action-btn.copied .btn-text {
  display: none;
}

.action-btn.copied .btn-success-text {
  display: block;
}

/* ==========================================================================
   Footer Component
   ========================================================================== */
#site-footer {
  border-top: 1px solid var(--header-border);
  background-color: var(--header-bg);
  padding: 3rem 2rem;
  text-align: center;
  position: relative;
  z-index: 10;
}

.footer-container {
  max-width: 1200px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.footer-container p {
  color: var(--text-secondary);
  font-size: 0.9rem;
}

.footer-container .footer-note {
  color: var(--text-muted);
  font-size: 0.8rem;
}

/* ==========================================================================
   Animation Definitions
   ========================================================================== */
@keyframes fadeIn {
  from {
    opacity: 0;
  }

  to {
    opacity: 1;
  }
}

@keyframes slideUp {
  from {
    opacity: 0;
    transform: translateY(16px);
  }

  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* ==========================================================================
   Responsive Media Queries (Mobile & Tablet)
   ========================================================================== */
@media (max-width: 900px) {
  .main-container {
    grid-template-columns: 1fr;
    gap: 3rem;
  }

  .sidebar {
    display: none;
    /* Hide TOC on mobile for layout simplicity, or make it horizontal */
  }

  #hero {
    padding: 7rem 1.5rem 3rem;
  }

  .hero-title {
    font-size: 2.25rem;
  }

  .hero-subtitle {
    font-size: 1rem;
  }

  .app-card {
    padding: 1rem 1.5rem;
  }

  #main-content {
    padding: 0 1.5rem 4rem;
  }

  .contact-card {
    flex-direction: column;
    align-items: stretch;
    padding: 1.5rem;
  }

  .contact-info {
    align-items: flex-start;
  }

  .action-btn {
    width: 100%;
    text-align: center;
  }
}

@media (max-width: 600px) {
  .data-grid {
    grid-template-columns: 1fr;
    gap: 1rem;
  }

  .app-card {
    flex-direction: column;
    align-items: center;
    text-align: center;
  }

  .hero-title {
    font-size: 2rem;
  }
}

/* Scroll-fade-in animation classes */
.fade-in-section {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.6s cubic-bezier(0.16, 1, 0.3, 1),
    transform 0.6s cubic-bezier(0.16, 1, 0.3, 1);
  will-change: opacity, transform;
}

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