:root {
  --bg: #f5f7fa;
  --card: #ffffff;
  --text: #1a1f36;
  --muted: #5a6478;
  --accent: #2563eb;
  --border: #e2e8f0;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Hiragino Kaku Gothic ProN",
    "Noto Sans JP", Meiryo, sans-serif;
  line-height: 1.8;
  -webkit-font-smoothing: antialiased;
}

.container {
  max-width: 760px;
  margin: 0 auto;
  padding: 40px 20px 80px;
}

.site-header {
  text-align: center;
  margin-bottom: 32px;
}

.site-header h1 {
  font-size: 1.9rem;
  margin: 0 0 8px;
}

.lead {
  color: var(--muted);
  margin: 0;
}

/* index card nav */
.card-nav {
  display: grid;
  gap: 16px;
  margin-top: 24px;
}

.card {
  display: block;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 20px 24px;
  text-decoration: none;
  color: inherit;
  transition: transform 0.12s ease, box-shadow 0.12s ease;
}

.card:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 24px rgba(37, 99, 235, 0.12);
}

.card-title {
  display: block;
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--accent);
}

.card-desc {
  display: block;
  color: var(--muted);
  font-size: 0.92rem;
  margin-top: 4px;
}

/* document pages */
.doc {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 40px 36px;
}

.doc h1 {
  font-size: 1.6rem;
  margin: 0 0 4px;
}

.doc .updated {
  color: var(--muted);
  font-size: 0.88rem;
  margin: 0 0 28px;
}

.doc h2 {
  font-size: 1.15rem;
  margin: 32px 0 10px;
  padding-bottom: 6px;
  border-bottom: 2px solid var(--border);
}

.doc h3 {
  font-size: 1rem;
  margin: 20px 0 6px;
}

.doc p,
.doc li {
  font-size: 0.98rem;
}

.doc ul {
  padding-left: 1.3em;
}

.doc a {
  color: var(--accent);
}

.back-link {
  display: inline-block;
  margin-bottom: 20px;
  color: var(--accent);
  text-decoration: none;
  font-size: 0.92rem;
}

.back-link:hover {
  text-decoration: underline;
}

.top-bar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 20px;
  gap: 12px;
  flex-wrap: wrap;
}

.top-bar .back-link {
  margin-bottom: 0;
}

.lang-switch {
  font-size: 0.85rem;
  color: var(--muted);
}

.lang-switch a {
  color: var(--accent);
  text-decoration: none;
}

.lang-switch a:hover {
  text-decoration: underline;
}

.lang-switch .current {
  color: var(--text);
  font-weight: 700;
}

.lang-switch .sep {
  margin: 0 6px;
  color: var(--border);
}

.site-footer {
  text-align: center;
  color: var(--muted);
  font-size: 0.85rem;
  margin-top: 40px;
}

.contact-box {
  background: #f0f4ff;
  border: 1px solid #dbe4ff;
  border-radius: 12px;
  padding: 16px 20px;
  margin-top: 12px;
}

@media (max-width: 480px) {
  .doc {
    padding: 28px 20px;
  }
}