/* ========== CSS Variables (Themes) ========== */
:root {
  /* Default theme: Dark */
  --color-text: #e5e7eb;
  --color-text-muted: #94a3b8;
  --color-text-secondary: #64748b;
  --color-bg-page: linear-gradient(180deg, #0b1220 0%, #0f1629 100%);
  --color-bg-page-solid: #0b1220;
  --color-bg-card: #0f172a;
  --color-bg-card-hover: #1a2332;
  --color-bg-badge: #0b1220;
  --color-border-card: #1f2937;
  --color-border-card-hover: #374151;
  --color-border-button: #334155;
  --color-arrow: #7c8796;
  --color-arrow-hover: #94a3b8;
  --color-section-divider: #243041;
  --color-shadow-card: rgba(0, 0, 0, 0.25);
  --color-shadow-card-hover: rgba(0, 0, 0, 0.35);
  --color-focus-ring: #60a5fa;
}

/* Theme: Dark */
[data-theme="dark"] {
  --color-text: #e5e7eb;
  --color-text-muted: #94a3b8;
  --color-text-secondary: #64748b;
  --color-bg-page: linear-gradient(180deg, #0b1220 0%, #0f1629 100%);
  --color-bg-page-solid: #0b1220;
  --color-bg-card: #0f172a;
  --color-bg-card-hover: #1a2332;
  --color-bg-badge: #0b1220;
  --color-border-card: #1f2937;
  --color-border-card-hover: #374151;
  --color-border-button: #334155;
  --color-arrow: #7c8796;
  --color-arrow-hover: #94a3b8;
  --color-section-divider: #243041;
  --color-shadow-card: rgba(0, 0, 0, 0.25);
  --color-shadow-card-hover: rgba(0, 0, 0, 0.35);
  --color-focus-ring: #60a5fa;
}

/* Theme: Light */
[data-theme="light"] {
  --color-text: #0f172a;
  --color-text-muted: #475569;
  --color-text-secondary: #64748b;
  --color-bg-page: linear-gradient(180deg, #f8fafc 0%, #eef2f7 100%);
  --color-bg-page-solid: #f8fafc;
  --color-bg-card: #ffffff;
  --color-bg-card-hover: #f9fafb;
  --color-bg-badge: #f1f5f9;
  --color-border-card: #e2e8f0;
  --color-border-card-hover: #cbd5e1;
  --color-border-button: #cbd5e1;
  --color-arrow: #94a3b8;
  --color-arrow-hover: #64748b;
  --color-section-divider: #cbd5e1;
  --color-shadow-card: rgba(15, 23, 42, 0.04);
  --color-shadow-card-hover: rgba(15, 23, 42, 0.08);
  --color-focus-ring: #3b82f6;
}

/* ========== Base Styles ========== */
* {
  box-sizing: border-box;
}

html {
  height: 100%;
  margin: 0;
  padding: 0;
  background: var(--color-bg-page-solid);
}

body {
  height: 100%;
  margin: 0;
  padding: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, "Noto Sans JP", "Hiragino Kaku Gothic ProN", "Yu Gothic UI", "YuGothic", Meiryo, sans-serif;
  line-height: 1.6;
  color: var(--color-text);
  background: var(--color-bg-page);
}

/* ========== Container ========== */
.container {
  max-width: 980px;
  margin: 0 auto;
  padding: 20px;
  min-height: 100vh;
}

/* ========== Header ========== */
.header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 40px;
}

.brand {
  font-size: 28px;
  font-weight: 700;
  letter-spacing: 0.02em;
  margin: 0;
}

.subtitle {
  margin: 8px 0 0 0;
  color: var(--color-text-muted);
  font-size: 14px;
}

/* ========== Theme Toggle ========== */
.theme-toggle {
  display: flex;
  align-items: center;
  gap: 12px;
}

.theme-label {
  font-size: 13px;
  color: var(--color-text-muted);
}

.toggle-switch {
  position: relative;
  display: inline-block;
  width: 48px;
  height: 24px;
}

.toggle-switch input {
  opacity: 0;
  width: 0;
  height: 0;
}

.slider {
  position: absolute;
  cursor: pointer;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: var(--color-border-card);
  transition: 0.3s;
  border-radius: 24px;
}

.slider:before {
  position: absolute;
  content: "";
  height: 18px;
  width: 18px;
  left: 3px;
  bottom: 3px;
  background-color: var(--color-text);
  transition: 0.3s;
  border-radius: 50%;
}

input:checked + .slider {
  background-color: var(--color-focus-ring);
}

input:checked + .slider:before {
  transform: translateX(24px);
}

/* ========== Section Title ========== */
.section-title {
  display: flex;
  align-items: center;
  gap: 12px;
  margin: 32px 0 20px;
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.08em;
  color: var(--color-text-muted);
  text-transform: uppercase;
}

.section-title:after {
  content: "";
  height: 1px;
  background: linear-gradient(90deg, var(--color-section-divider), transparent);
  flex: 1;
}

/* ========== Grid Layout ========== */
.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 20px;
  margin-bottom: 24px;
}

/* ========== Card ========== */
.card {
  display: flex;
  flex-direction: column;
  text-decoration: none;
  color: inherit;
  background: var(--color-bg-card);
  border: 1px solid var(--color-border-card);
  border-radius: 12px;
  padding: 24px;
  min-height: 140px;
  transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
  box-shadow: 0 1px 3px var(--color-shadow-card);
  position: relative;
}

.card:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 24px var(--color-shadow-card-hover);
  border-color: var(--color-border-card-hover);
}

.card:focus-visible {
  outline: 2px solid var(--color-focus-ring);
  outline-offset: 2px;
}

.card-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: 12px;
}

.card-title {
  font-size: 20px;
  font-weight: 600;
  letter-spacing: 0.01em;
  margin: 0;
}

.card-arrow {
  color: var(--color-arrow);
  transition: transform 0.2s ease, color 0.2s ease;
  font-size: 24px;
  line-height: 1;
  font-weight: 300;
}

.card:hover .card-arrow {
  transform: translateX(4px);
  color: var(--color-arrow-hover);
}

.card-description {
  color: var(--color-text-muted);
  font-size: 14px;
  line-height: 1.6;
  margin: 0;
  flex-grow: 1;
}

.card-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 16px;
}

.badge {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 4px 12px;
  border-radius: 999px;
  background: var(--color-bg-badge);
  border: 1px solid var(--color-border-card);
  color: var(--color-text-secondary);
  font-size: 12px;
  font-weight: 500;
}

/* ========== Footer ========== */
.footer {
  margin-top: 60px;
  padding-top: 24px;
  border-top: 1px solid var(--color-border-card);
  text-align: center;
  color: var(--color-text-secondary);
  font-size: 13px;
}

/* ========== Responsive ========== */
@media (max-width: 768px) {
  .container {
    padding: 24px 16px;
  }

  .header {
    flex-direction: row;
    align-items: flex-start;
    gap: 16px;
  }

  .brand {
    font-size: 24px;
  }

  .grid {
    grid-template-columns: 1fr;
  }
}