:root {
  --bg: #fafaf8;
  --fg: #1a1a1a;
  --fg-muted: #64748b;
  --accent: #2563eb;
  --accent-light: #dbeafe;
  --border: #e5e5e5;
  --card-bg: #ffffff;
  --toc-bg: #f8fafc;
  --sidebar-w: 280px;
  --right-sidebar-w: 260px;
  --header-h: 56px;
  --content-max-w: 860px;
  --radius: 12px;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f172a;
    --fg: #e2e8f0;
    --fg-muted: #94a3b8;
    --accent: #60a5fa;
    --accent-light: #1e3a5f;
    --border: #334155;
    --card-bg: #1e293b;
    --toc-bg: #1e293b;
  }
}
* { margin: 0; padding: 0; box-sizing: border-box; }
html {
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--header-h) + 20px);
  -webkit-text-size-adjust: 100%;
}
body {
  font-family: "Hiragino Kaku Gothic ProN", "Noto Sans JP", "Yu Gothic", "Meiryo", sans-serif;
  background: var(--bg);
  color: var(--fg);
  line-height: 1.85;
  font-size: clamp(14px, 0.9vw + 11px, 16px);
  overflow-x: hidden;
}

/* ========== Header ========== */
.header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--header-h);
  background: var(--accent);
  color: #fff;
  display: flex;
  align-items: center;
  padding: 0 24px;
  gap: 8px;
  z-index: 1000;
  box-shadow: 0 2px 8px rgba(0,0,0,.15);
}
.header h1 {
  font-size: clamp(14px, 1.8vw + 6px, 18px);
  font-weight: 700;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.header .subtitle {
  font-size: 12px;
  opacity: .8;
  white-space: nowrap;
}
.menu-toggle {
  display: none;
  align-items: center;
  justify-content: center;
  background: none;
  border: none;
  color: #fff;
  font-size: 22px;
  width: 40px;
  height: 40px;
  cursor: pointer;
  border-radius: 8px;
  flex-shrink: 0;
  transition: background .15s;
  -webkit-tap-highlight-color: transparent;
}
.menu-toggle:hover { background: rgba(255,255,255,.15); }

/* ========== Sidebar Overlay ========== */
.sidebar-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,.4);
  z-index: 899;
  opacity: 0;
  transition: opacity .3s ease;
  -webkit-tap-highlight-color: transparent;
}
.sidebar-overlay.visible {
  display: block;
  opacity: 1;
}

/* ========== Sidebar ========== */
.sidebar {
  position: fixed;
  top: var(--header-h);
  left: 0;
  width: var(--sidebar-w);
  height: calc(100vh - var(--header-h));
  overflow-y: auto;
  -webkit-overflow-scrolling: touch;
  background: var(--toc-bg);
  border-right: 1px solid var(--border);
  padding: 12px 0 24px;
  z-index: 900;
  transition: transform .3s cubic-bezier(.4,0,.2,1), visibility .3s;
}
.sidebar .toc h2 { display: none; }
.toc-section { margin-bottom: 4px; }
.toc-section-title {
  display: block;
  padding: 8px 20px;
  font-weight: 700;
  font-size: 13px;
  color: var(--accent);
  text-decoration: none;
  letter-spacing: .04em;
  transition: background .15s;
}
.toc-section-title:hover { background: var(--accent-light); }
.toc-section ul {
  list-style: none;
  padding: 0;
  margin: 0;
}
.toc-section li a {
  display: flex;
  align-items: center;
  padding: 6px 16px 6px 32px;
  font-size: 13px;
  color: var(--fg);
  text-decoration: none;
  border-left: 3px solid transparent;
  transition: all .15s;
  min-height: 36px;
}
.toc-section li a:hover,
.toc-section li a.active {
  background: var(--accent-light);
  border-left-color: var(--accent);
  color: var(--accent);
}

/* ========== Right Sidebar (Notes) ========== */
.right-sidebar {
  position: fixed;
  top: var(--header-h);
  right: 0;
  width: var(--right-sidebar-w);
  height: calc(100vh - var(--header-h));
  background: var(--toc-bg);
  border-left: 1px solid var(--border);
  z-index: 800;
  display: flex;
  flex-direction: column;
  padding: 16px;
}
.right-sidebar-title {
  font-size: 11px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: .06em;
  color: var(--fg-muted);
  margin-bottom: 8px;
  flex-shrink: 0;
}
.right-sidebar-chapter {
  font-size: 13px;
  font-weight: 700;
  color: var(--accent);
  margin-bottom: 12px;
  flex-shrink: 0;
  line-height: 1.4;
  min-height: 1.4em;
  overflow: hidden;
  text-overflow: ellipsis;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
}
.right-sidebar-textarea {
  flex: 1;
  width: 100%;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 12px;
  font-family: inherit;
  font-size: 13px;
  line-height: 1.6;
  color: var(--fg);
  background: var(--card-bg);
  resize: none;
  outline: none;
  transition: border-color .15s;
}
.right-sidebar-textarea:focus {
  border-color: var(--accent);
}
.right-sidebar-textarea::placeholder {
  color: var(--fg-muted);
}
.right-sidebar-status {
  font-size: 11px;
  color: var(--fg-muted);
  margin-top: 8px;
  flex-shrink: 0;
  min-height: 16px;
}

/* ========== Main ========== */
.main {
  margin-left: var(--sidebar-w);
  margin-right: var(--right-sidebar-w);
  margin-top: var(--header-h);
  padding: 32px 40px 100px;
}

/* ========== Parts & Chapters ========== */
.part {
  max-width: var(--content-max-w);
  margin: 0 auto 48px;
}
.part-title {
  font-size: clamp(20px, 2.5vw + 8px, 26px);
  font-weight: 800;
  color: var(--accent);
  border-bottom: 3px solid var(--accent);
  padding-bottom: 8px;
  margin-bottom: 28px;
}
.chapter {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px 32px;
  margin-bottom: 24px;
  box-shadow: 0 1px 3px rgba(0,0,0,.04);
}
.chapter > h2:first-of-type {
  font-size: clamp(17px, 1.8vw + 8px, 22px);
  font-weight: 800;
  color: var(--accent);
  border-left: 5px solid var(--accent);
  padding-left: 14px;
  margin-bottom: 20px;
}

/* ========== Headings ========== */
h3 {
  font-size: clamp(15px, 1.2vw + 8px, 18px);
  font-weight: 700;
  margin: 24px 0 12px;
  padding-bottom: 4px;
  border-bottom: 2px solid var(--border);
}
h4 {
  font-size: clamp(14px, 1vw + 8px, 16px);
  font-weight: 700;
  margin: 20px 0 8px;
  color: var(--accent);
}
h5 { font-size: 15px; font-weight: 700; margin: 16px 0 8px; }
h6 { font-size: 14px; font-weight: 700; margin: 12px 0 6px; }

/* ========== Text ========== */
p { margin: 8px 0; }
blockquote {
  background: var(--accent-light);
  border-left: 4px solid var(--accent);
  padding: 12px 16px;
  margin: 12px 0;
  border-radius: 0 8px 8px 0;
  font-size: 0.9em;
}
strong { color: var(--accent); font-weight: 700; }

/* ========== Lists ========== */
ul, ol { margin: 8px 0 8px 24px; }
li { margin: 4px 0; }
li > ul, li > ol { margin: 4px 0 4px 20px; }

/* ========== Tables ========== */
.table-wrap {
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  margin: 12px 0;
  border-radius: 8px;
  border: 1px solid var(--border);
  position: relative;
}
.table-wrap.scrollable::after {
  content: "";
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  width: 24px;
  background: linear-gradient(to right, transparent, rgba(0,0,0,.06));
  pointer-events: none;
  border-radius: 0 8px 8px 0;
}
.table-wrap table {
  margin: 0;
  border-radius: 0;
}
table {
  width: 100%;
  border-collapse: collapse;
  margin: 12px 0;
  font-size: clamp(12px, 0.8vw + 8px, 14px);
}
thead { background: var(--accent); color: #fff; }
th {
  padding: 10px 12px;
  text-align: left;
  font-weight: 600;
  white-space: nowrap;
}
td {
  padding: 8px 12px;
  border-bottom: 1px solid var(--border);
}
tbody tr:nth-child(even) { background: rgba(0,0,0,.02); }
tbody tr:hover { background: var(--accent-light); }

/* ========== Code ========== */
code {
  background: rgba(0,0,0,.06);
  padding: 2px 6px;
  border-radius: 4px;
  font-size: 0.88em;
  font-family: "Consolas", "Monaco", monospace;
}
pre {
  background: #1e293b;
  color: #e2e8f0;
  padding: 16px;
  border-radius: 8px;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  margin: 12px 0;
  font-size: 13px;
  line-height: 1.6;
}
pre code { background: none; padding: 0; color: inherit; }

/* ========== Horizontal rule ========== */
hr {
  border: none;
  border-top: 2px dashed var(--border);
  margin: 28px 0;
}

/* ========== Back to top ========== */
.back-top {
  position: fixed;
  bottom: 24px;
  right: 24px;
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background: var(--accent);
  color: #fff;
  border: none;
  font-size: 20px;
  cursor: pointer;
  box-shadow: 0 2px 12px rgba(0,0,0,.2);
  opacity: 0;
  visibility: hidden;
  transform: translateY(12px);
  transition: opacity .25s, visibility .25s, transform .25s;
  z-index: 999;
  -webkit-tap-highlight-color: transparent;
}
.back-top.visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}
.back-top:hover { opacity: .85; }

/* ========== Tablet (<=1024px) ========== */
@media (max-width: 1024px) {
  :root { --sidebar-w: 240px; }
  .right-sidebar { display: none; }
  .main { margin-right: 0; padding: 28px 28px 80px; }
  .chapter { padding: 24px; }
  .toc-section-title { font-size: 12px; }
  .toc-section li a { padding: 5px 14px 5px 26px; font-size: 12px; }
}

/* ========== Mobile (<=768px) ========== */
@media (max-width: 768px) {
  .menu-toggle { display: flex; }
  .sidebar {
    transform: translateX(-100%);
    visibility: hidden;
    width: 280px;
    box-shadow: 4px 0 24px rgba(0,0,0,.2);
  }
  .sidebar.open {
    transform: translateX(0);
    visibility: visible;
  }
  .main {
    margin-left: 0;
    padding: 20px 16px 80px;
  }
  .chapter { padding: 20px 16px; border-radius: 10px; }
  .header .subtitle { display: none; }
  th, td { padding: 8px 10px; }
  ul, ol { margin-left: 18px; }
  .toc-section li a {
    padding: 8px 16px 8px 28px;
    font-size: 14px;
    min-height: 44px;
  }
  .toc-section-title {
    padding: 10px 16px;
    font-size: 14px;
  }
}

/* ========== Small phone (<=480px) ========== */
@media (max-width: 480px) {
  .header h1 { font-size: 14px; }
  .main { padding: 16px 10px 80px; }
  .chapter { padding: 16px 12px; border-radius: 8px; }
  th, td { padding: 6px 8px; }
  .sidebar { width: 260px; }
  .back-top { bottom: 16px; right: 16px; }
}

/* ========== Very small phone (<=360px) ========== */
@media (max-width: 360px) {
  .main { padding: 12px 8px 80px; }
  .chapter { padding: 14px 10px; border-radius: 6px; }
  .header { padding: 0 8px; gap: 4px; }
  .header h1 { font-size: 13px; }
  th, td { padding: 4px 6px; }
  .sidebar { width: 240px; }
}

/* ========== Landscape phone ========== */
@media (max-width: 768px) and (orientation: landscape) {
  :root { --header-h: 44px; }
  .back-top { bottom: 12px; right: 12px; width: 40px; height: 40px; font-size: 16px; }
}

/* ========== Quiz Modal ========== */
.quiz-launcher {
  background: linear-gradient(90deg, var(--accent), #7c3aed);
  color: #fff !important;
  margin: 6px 12px 12px;
  border-radius: 8px;
  padding: 10px 16px !important;
  text-align: center;
  letter-spacing: .02em;
}
.quiz-launcher:hover { opacity: .9; background: linear-gradient(90deg, var(--accent), #7c3aed); }
.quiz-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,.55);
  z-index: 2000;
  align-items: flex-start;
  justify-content: center;
  padding: 40px 16px;
  overflow-y: auto;
  -webkit-overflow-scrolling: touch;
}
.quiz-overlay.visible { display: flex; }
.quiz-modal {
  background: var(--card-bg);
  color: var(--fg);
  width: 100%;
  max-width: 720px;
  border-radius: var(--radius);
  box-shadow: 0 12px 48px rgba(0,0,0,.3);
  display: flex;
  flex-direction: column;
  max-height: calc(100vh - 80px);
}
.quiz-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 24px;
  border-bottom: 1px solid var(--border);
  flex-shrink: 0;
}
.quiz-title { font-size: 16px; font-weight: 800; color: var(--accent); }
.quiz-close {
  background: none;
  border: none;
  font-size: 20px;
  cursor: pointer;
  color: var(--fg-muted);
  width: 32px;
  height: 32px;
  border-radius: 6px;
}
.quiz-close:hover { background: var(--accent-light); color: var(--accent); }
.quiz-body {
  padding: 16px 24px;
  overflow-y: auto;
  flex: 1;
}
.quiz-score {
  font-size: 18px;
  font-weight: 800;
  text-align: center;
  padding: 12px;
  margin-bottom: 16px;
  background: var(--accent-light);
  color: var(--accent);
  border-radius: 8px;
}
.quiz-item {
  padding: 14px 0;
  border-bottom: 1px dashed var(--border);
  font-size: 14px;
  line-height: 1.9;
}
.quiz-item:last-child { border-bottom: none; }
.quiz-q-num {
  display: inline-block;
  background: var(--accent);
  color: #fff;
  font-size: 11px;
  font-weight: 700;
  padding: 2px 8px;
  border-radius: 4px;
  margin-right: 8px;
}
.quiz-chapter {
  font-size: 11px;
  color: var(--fg-muted);
  margin-left: 8px;
}
.quiz-input {
  display: inline-block;
  border: none;
  border-bottom: 2px solid var(--accent);
  background: var(--accent-light);
  font-family: inherit;
  font-size: inherit;
  padding: 2px 8px;
  min-width: 80px;
  color: var(--fg);
  border-radius: 4px 4px 0 0;
  outline: none;
}
.quiz-input:focus { border-bottom-color: #7c3aed; }
.quiz-input.correct {
  background: rgba(34,197,94,.15);
  border-bottom-color: #22c55e;
  color: #15803d;
}
.quiz-input.wrong {
  background: rgba(239,68,68,.15);
  border-bottom-color: #ef4444;
  color: #b91c1c;
  text-decoration: line-through;
}
.quiz-answer {
  display: inline-block;
  margin-left: 6px;
  font-weight: 700;
  color: #15803d;
}
.quiz-footer {
  padding: 12px 24px;
  border-top: 1px solid var(--border);
  display: flex;
  gap: 8px;
  justify-content: flex-end;
  flex-shrink: 0;
}
.quiz-btn {
  padding: 8px 18px;
  border: 1px solid var(--border);
  background: var(--card-bg);
  color: var(--fg);
  border-radius: 8px;
  font-size: 13px;
  font-weight: 700;
  cursor: pointer;
  font-family: inherit;
}
.quiz-btn:hover { background: var(--accent-light); }
.quiz-btn-primary {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}
.quiz-btn-primary:hover { opacity: .85; background: var(--accent); }
.quiz-empty {
  text-align: center;
  color: var(--fg-muted);
  padding: 40px 20px;
}
.quiz-progress {
  font-size: 12px;
  font-weight: 700;
  color: var(--fg-muted);
  margin-left: auto;
  margin-right: 12px;
  white-space: nowrap;
}
.quiz-meta {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 6px;
  margin-bottom: 10px;
}
.quiz-question {
  font-size: 15px;
  line-height: 1.85;
  margin-bottom: 14px;
  padding: 12px 14px;
  background: var(--toc-bg);
  border-left: 3px solid var(--accent);
  border-radius: 6px;
  white-space: pre-wrap;
}
.quiz-choices {
  display: flex;
  flex-direction: column;
  gap: 8px;
  margin-bottom: 14px;
}
.quiz-choice {
  display: flex;
  align-items: flex-start;
  gap: 10px;
  text-align: left;
  padding: 10px 14px;
  border: 1.5px solid var(--border);
  background: var(--card-bg);
  color: var(--fg);
  border-radius: 8px;
  font-family: inherit;
  font-size: 14px;
  line-height: 1.7;
  cursor: pointer;
  transition: background .12s, border-color .12s;
}
.quiz-choice:hover:not(:disabled) {
  background: var(--accent-light);
  border-color: var(--accent);
}
.quiz-choice:disabled { cursor: default; }
.quiz-choice-num {
  flex-shrink: 0;
  width: 24px;
  height: 24px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  background: var(--accent-light);
  color: var(--accent);
  border-radius: 50%;
  font-weight: 700;
  font-size: 12px;
}
.quiz-choice-text { flex: 1; }
.quiz-choice.correct {
  border-color: #22c55e;
  background: rgba(34,197,94,.12);
}
.quiz-choice.correct .quiz-choice-num {
  background: #22c55e;
  color: #fff;
}
.quiz-choice.wrong {
  border-color: #ef4444;
  background: rgba(239,68,68,.12);
}
.quiz-choice.wrong .quiz-choice-num {
  background: #ef4444;
  color: #fff;
}
.quiz-explanation {
  margin-top: 12px;
  padding: 12px 14px;
  background: var(--toc-bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  font-size: 13px;
  line-height: 1.85;
}
.quiz-verdict {
  display: inline-block;
  font-weight: 800;
  font-size: 14px;
  margin-bottom: 8px;
}
.quiz-verdict.ok { color: #15803d; }
.quiz-verdict.ng { color: #b91c1c; }
.quiz-explanation-body { color: var(--fg); white-space: pre-wrap; }
.quiz-result-msg {
  text-align: center;
  color: var(--fg-muted);
  font-size: 13px;
  margin-top: 12px;
}
@media (max-width: 480px) {
  .quiz-overlay { padding: 16px 8px; }
  .quiz-header, .quiz-body, .quiz-footer { padding-left: 16px; padding-right: 16px; }
  .quiz-modal { max-height: calc(100vh - 32px); }
  .quiz-progress { font-size: 11px; }
  .quiz-question { font-size: 14px; }
  .quiz-choice { font-size: 13px; padding: 9px 12px; }
}

/* ========== Fill-in-blank ========== */
.fillin-launcher {
  background: linear-gradient(90deg, #7c3aed, #ec4899);
  color: #fff !important;
  margin: 0 12px 12px;
  border-radius: 8px;
  padding: 10px 16px !important;
  text-align: center;
  letter-spacing: .02em;
}
.fillin-launcher:hover { opacity: .9; background: linear-gradient(90deg, #7c3aed, #ec4899); }
.fillin-paragraph {
  background: var(--toc-bg);
  border-left: 3px solid #7c3aed;
  border-radius: 6px;
  padding: 14px 16px;
  font-size: 15px;
  line-height: 2;
  margin-bottom: 12px;
}
.fillin-line { margin: 4px 0; }
.fillin-li { margin: 4px 0 4px 8px; }
.fillin-hint {
  font-size: 12px;
  color: var(--fg-muted);
  margin-bottom: 8px;
  padding: 6px 10px;
  background: var(--accent-light);
  border-radius: 6px;
}
.fillin-input {
  display: inline-block;
  border: none;
  border-bottom: 2px solid #7c3aed;
  background: rgba(124,58,237,.08);
  font-family: inherit;
  font-size: inherit;
  padding: 2px 10px;
  min-width: 100px;
  color: var(--fg);
  border-radius: 4px 4px 0 0;
  outline: none;
  margin: 0 2px;
}
.fillin-input:focus {
  border-bottom-color: #ec4899;
  background: rgba(236,72,153,.10);
}
.fillin-input.correct {
  background: rgba(34,197,94,.18);
  border-bottom-color: #22c55e;
  color: #15803d;
  font-weight: 700;
}
.fillin-input.wrong {
  background: rgba(239,68,68,.18);
  border-bottom-color: #ef4444;
  color: #b91c1c;
  text-decoration: line-through;
}
.fillin-answer-correct {
  font-weight: 700;
  color: #15803d;
  margin-left: 4px;
}
.fillin-answer-hl {
  background: rgba(34,197,94,.18);
  padding: 0 4px;
  border-radius: 3px;
}
@media (max-width: 480px) {
  .fillin-paragraph { font-size: 14px; padding: 12px 14px; }
  .fillin-input { min-width: 80px; font-size: 14px; }
}

/* 設定画面 */
.fillin-setup {
  display: flex;
  flex-direction: column;
  gap: 18px;
  padding: 4px;
}
.fillin-setup-section {
  display: flex;
  flex-direction: column;
  gap: 8px;
}
.fillin-setup-label {
  font-size: 13px;
  font-weight: 700;
  color: var(--accent);
  letter-spacing: .03em;
}
.fillin-setup-actions {
  display: flex;
  gap: 6px;
}
.fillin-btn-mini {
  padding: 4px 10px !important;
  font-size: 11px !important;
  font-weight: 600 !important;
}
.fillin-cats {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(160px, 1fr));
  gap: 6px 10px;
}
.fillin-cat {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 6px 10px;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: var(--card-bg);
  cursor: pointer;
  font-size: 13px;
  transition: background .12s, border-color .12s;
}
.fillin-cat:hover { background: var(--accent-light); }
.fillin-cat input[type=checkbox] {
  width: 16px;
  height: 16px;
  accent-color: #7c3aed;
  cursor: pointer;
}
.fillin-cat em {
  color: var(--fg-muted);
  font-style: normal;
  font-size: 11px;
  margin-left: 2px;
}
.fillin-size-select {
  padding: 6px 10px;
  font-family: inherit;
  font-size: 13px;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: var(--card-bg);
  color: var(--fg);
  width: fit-content;
  min-width: 120px;
  cursor: pointer;
}
.fillin-setup-start {
  align-items: stretch;
  margin-top: 8px;
}
.fillin-setup-start .quiz-btn {
  padding: 12px 24px;
  font-size: 14px;
}
@media (max-width: 480px) {
  .fillin-cats { grid-template-columns: 1fr; }
}

/* ========== Print ========== */
@media print {
  .header, .sidebar, .right-sidebar, .back-top, .menu-toggle, .sidebar-overlay { display: none !important; }
  .main { margin: 0; padding: 0; max-width: 100%; }
  .chapter { break-inside: avoid; border: none; box-shadow: none; padding: 0; margin-bottom: 16px; }
  .part { break-before: page; }
  body { font-size: 11pt; line-height: 1.6; }
  table { font-size: 10pt; }
}