:root {
  --bg: #ffffff;
  --fg: #222222;
  --muted: #666666;
  --brand: #4c8bf5;
  --border: #dddddd;
  --panel: #f9f9fb;
  --link: #2a63d4;
  --close-btn: #dce8ff;
  --close-btn-hover: #c3d6ff;
}

* {
  box-sizing: border-box;
}

html, body {
  height: 100%;
}

body {
  margin: 0;
  color: var(--fg);
  background: var(--bg);
  font: 16px/1.7 system-ui, -apple-system, "Segoe UI", Roboto, "Noto Sans JP", "Hiragino Kaku Gothic ProN", Meiryo, sans-serif;
  -webkit-text-size-adjust: 100%;
}

a {
  color: var(--link);
  text-decoration: underline;
}

a:hover {
  opacity: 0.9;
}

.container {
  max-width: 1100px;
  margin: 0 auto;
  padding: clamp(12px, 2vw, 24px);
}

/* Header / Footer */
.site-header,
.site-footer {
  border-bottom: 1px solid var(--border);
  background: var(--panel);
}

.site-footer {
  border-top: 1px solid var(--border);
  border-bottom: none;
}

.site-title {
  margin: 0 0 8px 0;
  font-size: clamp(20px, 2.6vw, 28px);
  letter-spacing: 0.02em;
  color: var(--fg);
}

/* Navigation Buttons */
.doc-nav {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

.doc-nav a {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 8px 14px;
  border: 1px solid var(--border);
  border-radius: 999px;
  text-decoration: none;
  color: var(--fg);
  background: #ffffff;
  transition: all 0.2s ease;
}

.doc-nav a:hover {
  background: #f0f4ff;
  border-color: #c5d7ff;
}

.doc-nav a[aria-current="page"] {
  background: var(--brand);
  color: white;
  border-color: var(--brand);
}

/* Close Button */
.close-btn {
  display: inline-block;
  padding: 8px 16px;
  border: none;
  border-radius: 999px;
  background: var(--close-btn);
  color: #1b3a7a;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.2s ease;
}

.close-btn:hover {
  background: var(--close-btn-hover);
}

/* Main Layout */
main.container {
  display: grid;
  grid-template-columns: 280px 1fr;
  gap: clamp(16px, 2vw, 28px);
  align-items: start;
}

/* TOC */
.toc {
  position: sticky;
  top: 16px;
  border: 1px solid var(--border);
  background: var(--panel);
  border-radius: 12px;
  padding: 16px;
}

.toc h2 {
  margin: 0 0 8px 0;
  font-size: 16px;
  color: var(--muted);
}

.toc ol {
  margin: 0;
  padding-left: 18px;
}

.toc a {
  text-decoration: none;
  color: var(--fg);
}

.toc a:hover {
  text-decoration: underline;
}

/* Document Body */
.doc {
  border: 1px solid var(--border);
  background: #ffffff;
  border-radius: 12px;
  padding: clamp(16px, 2vw, 28px);
  box-shadow: 0 2px 4px rgba(0,0,0,0.05);
}

.doc h2 {
  margin-top: 0;
  font-size: clamp(18px, 2.2vw, 24px);
  border-left: 4px solid var(--brand);
  padding-left: 10px;
  color: var(--fg);
}

.doc p,
.doc li {
  word-break: break-word;
}

.doc ul {
  padding-left: 20px;
}

/* Footer */
.site-footer .container {
  font-size: 14px;
  color: var(--muted);
  text-align: center;
  padding: 12px 0;
}

/* Small screens */
@media (max-width: 860px) {
  main.container {
    grid-template-columns: 1fr;
  }
  .toc {
    position: static;
    order: -1;
  }
}