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

:root {
  --color-bg: #0f1117;
  --color-surface: #1a1d27;
  --color-surface2: #232736;
  --color-border: #2e3347;
  --color-primary: #d97706;
  --color-primary-light: #fbbf24;
  --color-accent: #6366f1;
  --color-accent-light: #818cf8;
  --color-success: #10b981;
  --color-text: #e2e8f0;
  --color-text-muted: #94a3b8;
  --color-text-dim: #64748b;
  --font-sans: 'Noto Sans JP', 'Hiragino Kaku Gothic ProN', sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Courier New', monospace;
  --radius: 8px;
  --radius-lg: 16px;
  --shadow: 0 4px 24px rgba(0,0,0,0.4);
  --transition: 0.2s ease;
}

html { scroll-behavior: smooth; }

body {
  font-family: var(--font-sans);
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.7;
  font-size: 16px;
}

a { color: var(--color-accent-light); text-decoration: none; }
a:hover { color: var(--color-primary-light); }

/* ===== Header / Nav ===== */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(15,17,23,0.92);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-border);
  padding: 0 2rem;
  height: 64px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.site-logo {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--color-text);
  text-decoration: none;
}

.site-logo .logo-icon {
  width: 32px;
  height: 32px;
  background: linear-gradient(135deg, var(--color-primary), var(--color-accent));
  border-radius: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1rem;
}

.site-nav {
  display: flex;
  align-items: center;
  gap: 0.25rem;
}

.nav-link {
  padding: 0.4rem 0.9rem;
  border-radius: var(--radius);
  color: var(--color-text-muted);
  font-size: 0.9rem;
  transition: var(--transition);
}

.nav-link:hover, .nav-link.active {
  background: var(--color-surface);
  color: var(--color-text);
}

.nav-link.active {
  color: var(--color-primary-light);
}

/* ===== Sidebar layout ===== */
.page-wrapper {
  display: grid;
  grid-template-columns: 260px 1fr;
  min-height: calc(100vh - 64px);
}

.sidebar {
  position: sticky;
  top: 64px;
  height: calc(100vh - 64px);
  overflow-y: auto;
  background: var(--color-surface);
  border-right: 1px solid var(--color-border);
  padding: 1.5rem 1rem;
}

.sidebar-title {
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--color-text-dim);
  padding: 0 0.5rem;
  margin-bottom: 0.75rem;
  margin-top: 1.25rem;
}

.sidebar-title:first-child { margin-top: 0; }

.sidebar-link {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.45rem 0.5rem;
  border-radius: var(--radius);
  color: var(--color-text-muted);
  font-size: 0.875rem;
  transition: var(--transition);
  line-height: 1.4;
}

.sidebar-link:hover {
  background: var(--color-surface2);
  color: var(--color-text);
}

.sidebar-link.active {
  background: rgba(217,119,6,0.12);
  color: var(--color-primary-light);
}

.sidebar-link .link-num {
  font-size: 0.75rem;
  color: var(--color-text-dim);
  min-width: 20px;
}

/* ===== Main content ===== */
.main-content {
  padding: 3rem 4rem;
  max-width: 860px;
  min-width: 0; /* グリッドアイテムのデフォルト min-width:auto によるはみ出しを防ぐ */
  overflow-x: hidden;
}

/* ===== kbd ===== */
kbd {
  font-family: var(--font-mono);
  font-size: 0.8em;
  background: var(--color-surface2);
  border: 1px solid var(--color-border);
  border-bottom-width: 2px;
  border-radius: 4px;
  padding: 0.1em 0.45em;
  color: var(--color-text);
}

/* ===== Hero (top page) ===== */
.hero {
  padding: 5rem 4rem 4rem;
  text-align: center;
  background: radial-gradient(ellipse 80% 60% at 50% 0%, rgba(217,119,6,0.08) 0%, transparent 70%);
  border-bottom: 1px solid var(--color-border);
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  background: rgba(99,102,241,0.12);
  border: 1px solid rgba(99,102,241,0.3);
  color: var(--color-accent-light);
  font-size: 0.8rem;
  font-weight: 600;
  padding: 0.3rem 0.9rem;
  border-radius: 99px;
  margin-bottom: 1.5rem;
}

.hero h1 {
  font-size: clamp(2rem, 5vw, 3.2rem);
  font-weight: 800;
  line-height: 1.2;
  margin-bottom: 1rem;
  background: linear-gradient(135deg, #fff 30%, var(--color-primary-light));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero p {
  font-size: 1.1rem;
  color: var(--color-text-muted);
  max-width: 580px;
  margin: 0 auto 2.5rem;
}

.hero-actions {
  display: flex;
  gap: 1rem;
  justify-content: center;
  flex-wrap: wrap;
}

/* ===== Buttons ===== */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.7rem 1.6rem;
  border-radius: var(--radius);
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
  border: none;
  text-decoration: none;
}

.btn-primary {
  background: var(--color-primary);
  color: #fff;
}

.btn-primary:hover {
  background: var(--color-primary-light);
  color: #000;
  transform: translateY(-1px);
  box-shadow: 0 8px 24px rgba(217,119,6,0.35);
}

.btn-outline {
  background: transparent;
  border: 1px solid var(--color-border);
  color: var(--color-text-muted);
}

.btn-outline:hover {
  border-color: var(--color-accent-light);
  color: var(--color-accent-light);
  transform: translateY(-1px);
}

/* ===== Chapter cards ===== */
.chapters-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 1.25rem;
  padding: 3rem 4rem;
}

.chapter-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 1.75rem;
  transition: var(--transition);
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  text-decoration: none;
  color: inherit;
}

.chapter-card:hover {
  border-color: var(--color-primary);
  transform: translateY(-3px);
  box-shadow: 0 12px 40px rgba(217,119,6,0.15);
  color: inherit;
}

.chapter-card .card-num {
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  color: var(--color-primary);
  text-transform: uppercase;
}

.chapter-card h3 {
  font-size: 1.1rem;
  font-weight: 700;
  line-height: 1.4;
}

.chapter-card p {
  font-size: 0.875rem;
  color: var(--color-text-muted);
  flex: 1;
}

.chapter-card .card-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-top: 0.5rem;
}

.tag {
  display: inline-block;
  font-size: 0.72rem;
  font-weight: 600;
  padding: 0.2rem 0.6rem;
  border-radius: 99px;
  background: rgba(99,102,241,0.12);
  color: var(--color-accent-light);
  border: 1px solid rgba(99,102,241,0.2);
}

.tag.beginner {
  background: rgba(16,185,129,0.1);
  color: #6ee7b7;
  border-color: rgba(16,185,129,0.2);
}

/* ===== Typography in article ===== */
.article h1 {
  font-size: 2rem;
  font-weight: 800;
  margin-bottom: 0.5rem;
  line-height: 1.3;
}

.article .chapter-label {
  font-size: 0.8rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--color-primary);
  margin-bottom: 0.5rem;
}

.article .lead {
  font-size: 1.1rem;
  color: var(--color-text-muted);
  margin-bottom: 2.5rem;
  border-bottom: 1px solid var(--color-border);
  padding-bottom: 1.5rem;
}

.article h2 {
  font-size: 1.4rem;
  font-weight: 700;
  margin: 2.5rem 0 1rem;
  padding-left: 0.75rem;
  border-left: 3px solid var(--color-primary);
}

.article h3 {
  font-size: 1.1rem;
  font-weight: 700;
  margin: 1.75rem 0 0.75rem;
  color: var(--color-text);
}

.article p {
  margin-bottom: 1rem;
  color: var(--color-text-muted);
}

.article ul, .article ol {
  margin: 0.75rem 0 1.25rem 1.5rem;
  color: var(--color-text-muted);
}

.article li {
  margin-bottom: 0.4rem;
}

.article strong {
  color: var(--color-text);
  font-weight: 600;
}

/* ===== Callout boxes ===== */
.callout {
  border-radius: var(--radius);
  padding: 1.25rem 1.5rem;
  margin: 1.5rem 0;
  display: flex;
  gap: 1rem;
  font-size: 0.9rem;
}

.callout-icon { font-size: 1.2rem; flex-shrink: 0; margin-top: 0.1rem; }

.callout-info {
  background: rgba(99,102,241,0.08);
  border: 1px solid rgba(99,102,241,0.2);
  color: #c7d2fe;
}

.callout-tip {
  background: rgba(16,185,129,0.08);
  border: 1px solid rgba(16,185,129,0.2);
  color: #a7f3d0;
}

.callout-warning {
  background: rgba(245,158,11,0.08);
  border: 1px solid rgba(245,158,11,0.2);
  color: #fde68a;
}

.callout strong {
  display: block;
  margin-bottom: 0.25rem;
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  opacity: 0.7;
}

/* ===== Code blocks ===== */
.code-block {
  background: #0d1117;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  margin: 1.25rem 0;
  overflow: hidden;
}

.code-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.5rem 1rem;
  background: var(--color-surface2);
  border-bottom: 1px solid var(--color-border);
  font-size: 0.75rem;
  color: var(--color-text-dim);
}

.code-dots {
  display: flex;
  gap: 5px;
}

.code-dots span {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  display: block;
}

.code-dots span:nth-child(1) { background: #ff5f57; }
.code-dots span:nth-child(2) { background: #febc2e; }
.code-dots span:nth-child(3) { background: #28c840; }

.code-block pre {
  padding: 1.25rem 1.5rem;
  overflow-x: auto;
  font-family: var(--font-mono);
  font-size: 0.875rem;
  line-height: 1.6;
  color: #c9d1d9;
}

.code-block code { font-family: inherit; }

.token-keyword { color: #ff7b72; }
.token-string  { color: #a5d6ff; }
.token-comment { color: #8b949e; font-style: italic; }
.token-func    { color: #d2a8ff; }
.token-num     { color: #79c0ff; }

/* ===== Inline code ===== */
code:not(.code-block code) {
  font-family: var(--font-mono);
  font-size: 0.85em;
  background: var(--color-surface2);
  border: 1px solid var(--color-border);
  padding: 0.15em 0.45em;
  border-radius: 4px;
  color: var(--color-primary-light);
}

/* ===== Feature grid ===== */
.feature-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 1rem;
  margin: 1.5rem 0;
}

.feature-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 1.25rem;
  transition: var(--transition);
}

.feature-card:hover {
  border-color: var(--color-accent);
}

.feature-card .feat-icon {
  font-size: 1.5rem;
  margin-bottom: 0.6rem;
}

.feature-card h4 {
  font-size: 0.95rem;
  font-weight: 700;
  margin-bottom: 0.3rem;
}

.feature-card p {
  font-size: 0.82rem;
  color: var(--color-text-muted);
  margin: 0;
}

/* ===== Steps ===== */
.step-list {
  list-style: none;
  margin: 1.5rem 0;
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.step-item {
  display: flex;
  gap: 1rem;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 1.25rem;
  transition: var(--transition);
}

.step-item:hover { border-color: var(--color-primary); }

.step-num {
  width: 32px;
  height: 32px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--color-primary), var(--color-accent));
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 800;
  font-size: 0.85rem;
  color: #fff;
  flex-shrink: 0;
}

.step-content h4 {
  font-size: 0.95rem;
  font-weight: 700;
  margin-bottom: 0.3rem;
}

.step-content p {
  font-size: 0.875rem;
  color: var(--color-text-muted);
  margin: 0;
}

/* ===== OS tabs ===== */
.tab-bar {
  display: flex;
  gap: 0.25rem;
  border-bottom: 1px solid var(--color-border);
  margin-bottom: 0;
}

.tab-btn {
  padding: 0.5rem 1.1rem;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--color-text-muted);
  background: none;
  border: none;
  border-bottom: 2px solid transparent;
  cursor: pointer;
  transition: var(--transition);
  margin-bottom: -1px;
}

.tab-btn.active {
  color: var(--color-primary-light);
  border-bottom-color: var(--color-primary);
}

.tab-panel { display: none; }
.tab-panel.active { display: block; }

/* ===== Table ===== */
.article table {
  width: 100%;
  border-collapse: collapse;
  margin: 1.5rem 0;
  font-size: 0.875rem;
}

.article th {
  text-align: left;
  padding: 0.75rem 1rem;
  background: var(--color-surface2);
  color: var(--color-text-muted);
  font-size: 0.78rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  border-bottom: 1px solid var(--color-border);
}

.article td {
  padding: 0.75rem 1rem;
  border-bottom: 1px solid var(--color-border);
  color: var(--color-text-muted);
}

.article tr:last-child td { border-bottom: none; }

/* ===== Page nav ===== */
.page-nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 3rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--color-border);
  gap: 1rem;
}

.page-nav a {
  display: flex;
  flex-direction: column;
  gap: 0.2rem;
  padding: 0.75rem 1.25rem;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  transition: var(--transition);
  max-width: 240px;
}

.page-nav a:hover {
  border-color: var(--color-primary);
  color: var(--color-text);
}

.page-nav .nav-label {
  font-size: 0.72rem;
  color: var(--color-text-dim);
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.page-nav .nav-title {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--color-text-muted);
}

.page-nav a:hover .nav-title { color: var(--color-primary-light); }

.page-nav .next { text-align: right; margin-left: auto; }

/* ===== Access cards (3種類の使い方) ===== */
.access-cards {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 1rem;
  margin: 1.25rem 0 1.5rem;
}

.access-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 1.5rem 1.25rem;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  transition: var(--transition);
}

.access-card:hover {
  border-color: var(--color-accent);
  transform: translateY(-2px);
  box-shadow: 0 8px 28px rgba(99,102,241,0.12);
}

.access-card--highlight {
  border-color: var(--color-primary);
  background: linear-gradient(160deg, rgba(217,119,6,0.06) 0%, var(--color-surface) 60%);
}

.access-card--highlight:hover {
  border-color: var(--color-primary-light);
  box-shadow: 0 8px 28px rgba(217,119,6,0.18);
}

.access-icon {
  font-size: 1.8rem;
  line-height: 1;
}

.access-badge {
  display: inline-block;
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--color-text-dim);
}

.access-card--highlight .access-badge {
  color: var(--color-primary);
}

.access-card h4 {
  font-size: 1rem;
  font-weight: 700;
  margin: 0;
  color: var(--color-text);
}

.access-card p {
  font-size: 0.82rem;
  color: var(--color-text-muted);
  margin: 0;
  line-height: 1.5;
}

.access-card ul {
  margin: 0.25rem 0 0 1.1rem;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 0.2rem;
}

.access-card li {
  font-size: 0.78rem;
  color: var(--color-text-dim);
  margin: 0;
}

/* ===== Footer ===== */
.site-footer {
  text-align: center;
  padding: 2rem;
  border-top: 1px solid var(--color-border);
  color: var(--color-text-dim);
  font-size: 0.8rem;
}

/* ===== Hamburger button ===== */
.nav-toggle {
  display: none;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  gap: 5px;
  width: 36px;
  height: 36px;
  background: none;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  cursor: pointer;
  padding: 6px;
  flex-shrink: 0;
}

.nav-toggle span {
  display: block;
  width: 18px;
  height: 2px;
  background: var(--color-text-muted);
  border-radius: 2px;
  transition: var(--transition);
}

.nav-toggle[aria-expanded="true"] span:nth-child(1) {
  transform: rotate(45deg) translate(5px, 5px);
}
.nav-toggle[aria-expanded="true"] span:nth-child(2) {
  opacity: 0;
}
.nav-toggle[aria-expanded="true"] span:nth-child(3) {
  transform: rotate(-45deg) translate(5px, -5px);
}

/* ===== Responsive ===== */
@media (max-width: 900px) {
  .page-wrapper { grid-template-columns: 1fr; }
  .sidebar { display: none; }
  .main-content { padding: 2rem 1.5rem; max-width: 100%; }
  .hero { padding: 3rem 1.5rem; }
  .chapters-grid { padding: 2rem 1.5rem; }
}

@media (max-width: 768px) {
  .nav-toggle { display: flex; }

  .site-nav {
    display: none;
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    flex-direction: column;
    background: rgba(15,17,23,0.97);
    backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--color-border);
    padding: 0.75rem;
    gap: 0.25rem;
    z-index: 99;
  }

  .site-nav.open { display: flex; }

  .nav-link {
    padding: 0.65rem 1rem;
    font-size: 0.95rem;
  }

  /* テーブル横スクロール */
  .article table {
    display: block;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
  }

  /* ページナビ縦積み */
  .page-nav {
    flex-direction: column;
    gap: 0.75rem;
  }
  .page-nav a { max-width: 100%; }
  .page-nav .next { margin-left: 0; text-align: left; }

  /* 章カード */
  .chapters-grid { grid-template-columns: 1fr; }

  /* フォントサイズ調整 */
  .article h1 { font-size: 1.5rem; }
  .article h2 { font-size: 1.2rem; }
}