:root {
  --bg: #edf1ef;
  --surface: #f8faf8;
  --surface-soft: #f2f5f3;
  --surface-alt: #e8eeeb;
  --line: #d5ded9;
  --line-strong: #c3cec8;
  --ink: #24323a;
  --muted: #66757c;
  --muted-strong: #4b5d64;
  --primary: #3f6d68;
  --primary-soft: #dbe9e5;
  --primary-strong: #315752;
  --green: #3f8067;
  --green-soft: #e3f0e8;
  --amber: #9b7441;
  --amber-soft: #f4eadb;
  --rose: #9d616a;
  --rose-soft: #f4e7ea;
  --shadow: 0 10px 24px rgba(36, 50, 58, 0.035);
  --radius: 12px;
  --radius-sm: 9px;
  --max-width: 1180px;
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; min-height: 100%; }
body {
  font-family: -apple-system, BlinkMacSystemFont, 'PingFang SC', 'Segoe UI', sans-serif;
  background: linear-gradient(180deg, #eef2f0 0%, #e9eeeb 100%);
  color: var(--ink);
}
button, input, select, textarea { font: inherit; }
a { color: inherit; text-decoration: none; }
h1, h2, h3, h4, p { margin: 0; }
ul { margin: 0; padding-left: 18px; }

.app-shell {
  min-height: 100vh;
  display: grid;
  transition: grid-template-columns .2s ease;
}
.app-shell.overview-layout { grid-template-columns: minmax(0, 1fr); }
.app-shell.workspace-layout { grid-template-columns: 276px minmax(0, 1fr); }
.app-shell.workspace-layout.chapter-sidebar-collapsed { grid-template-columns: 76px minmax(0, 1fr); }

.sidebar {
  background: #f1f4f2;
  border-right: 1px solid var(--line);
  padding: 20px 18px;
  position: sticky;
  top: 0;
  height: 100vh;
  overflow: auto;
}
.sidebar-empty { display: none; }
.sidebar.collapsed {
  padding: 20px 10px;
  overflow: hidden;
}
.rail-brand {
  display: flex;
  gap: 12px;
  align-items: center;
  margin-bottom: 18px;
}
.rail-brand-collapsed {
  flex-direction: column;
  align-items: center;
}
.rail-mark {
  width: 38px;
  height: 38px;
  border-radius: 12px;
  display: grid;
  place-items: center;
  background: #d8e5e0;
  color: var(--primary-strong);
  font-weight: 700;
}
.rail-brand h1 { font-size: 17px; }
.rail-brand p { margin-top: 4px; color: var(--muted); font-size: 12px; }
.rail-toolbar {
  display: flex;
  justify-content: flex-end;
  margin-bottom: 14px;
}
.rail-collapse-btn {
  width: 38px;
  height: 38px;
  padding: 0;
}
.rail-panel {
  background: rgba(248, 250, 248, 0.88);
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 14px;
  margin-bottom: 14px;
  box-shadow: 0 4px 10px rgba(36, 50, 58, 0.025);
}
.rail-progress .muted { margin-top: 8px; }
.rail-head {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 10px;
  font-size: 13px;
}
.rail-head span { color: var(--muted-strong); }
.rail-stat {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  font-size: 13px;
  padding: 8px 0;
  border-bottom: 1px solid rgba(215, 226, 232, 0.7);
}
.rail-stat:last-child { border-bottom: 0; }
.rail-stat span { color: var(--muted); }
.rail-stat strong { color: var(--ink); }
.rail-panel h3 { font-size: 14px; margin-bottom: 10px; }
.chapter-tree.compact { display: grid; gap: 8px; }
.chapter-part { display: grid; gap: 6px; }
.chapter-part h4 {
  margin: 2px 0 0;
  font-size: 12px;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: .08em;
}
.chapter-link {
  width: 100%;
  text-align: left;
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 9px 11px;
  background: var(--surface);
  color: var(--ink);
  cursor: pointer;
  transition: .18s ease;
}
.chapter-link:hover { border-color: var(--line-strong); background: var(--surface-soft); }
.chapter-link.active { border-color: var(--primary); background: #f1f6f4; }
.chapter-link strong { display: block; font-size: 13px; line-height: 1.28; }
.chapter-link span { display: block; margin-top: 3px; font-size: 11px; line-height: 1.42; color: var(--muted); }
.chapter-link-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 8px;
}
.chapter-link-meta {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 6px 10px;
  margin-top: 7px;
  font-size: 11px;
  color: var(--muted-strong);
}
.chapter-node {
  display: grid;
  gap: 6px;
}
.chapter-node-head {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 30px;
  gap: 6px;
  align-items: stretch;
}
.chapter-expand-btn {
  width: 30px;
  height: 30px;
  padding: 0;
  min-height: 30px;
  border-radius: 9px;
  font-size: 11px;
}
.section-tree {
  display: grid;
  gap: 6px;
  padding-left: 10px;
}
.section-link {
  width: 100%;
  text-align: left;
  border: 1px solid rgba(197, 208, 202, 0.85);
  border-radius: 9px;
  padding: 8px 10px;
  background: rgba(248, 250, 248, 0.92);
  color: var(--ink);
  cursor: pointer;
  transition: .18s ease;
}
.section-link:hover { border-color: var(--line-strong); background: var(--surface-soft); }
.section-link.active { border-color: var(--primary); background: #ecf4f1; }
.section-link-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 6px;
}
.section-link strong { display: block; font-size: 12px; line-height: 1.28; }
.section-link span { display: block; margin-top: 2px; font-size: 11px; line-height: 1.38; color: var(--muted); }
.chapter-outline-list, .stack-xs, .featured-list, .dense-list, .timeline-list, .wrongbook-list, .point-list, .simulator-card-list { display: grid; gap: 10px; }
.outline-chip, .map-row, .featured-item, .timeline-item {
  padding: 10px 12px;
  border-radius: 10px;
  background: var(--surface-alt);
  color: var(--muted-strong);
  font-size: 13px;
}
.featured-item, .timeline-item { display: grid; gap: 4px; }
.timeline-item small { color: var(--muted); }

.main-shell { min-width: 0; display: grid; grid-template-rows: auto minmax(0, 1fr); }
.topbar {
  position: sticky;
  top: 0;
  z-index: 10;
  background: rgba(237, 241, 239, 0.9);
  backdrop-filter: blur(14px);
  border-bottom: 1px solid rgba(197, 208, 202, 0.82);
  padding: 16px 24px;
}
.topbar-inner {
  width: min(100%, var(--max-width));
  margin: 0 auto;
  display: flex;
  justify-content: space-between;
  align-items: flex-end;
  gap: 18px;
  flex-wrap: wrap;
}
.topbar-left {
  display: flex;
  gap: 14px;
  align-items: flex-start;
}
.topbar-copy {
  display: grid;
  gap: 2px;
}
.topbar-right {
  display: flex;
  gap: 14px;
  align-items: center;
  justify-content: flex-end;
  flex-wrap: wrap;
}
.account-bar {
  display: flex;
  gap: 10px;
  align-items: center;
  flex-wrap: wrap;
}
.sync-pill {
  display: inline-flex;
  align-items: center;
  padding: 8px 12px;
  border-radius: 999px;
  background: #eef3f0;
  border: 1px solid var(--line);
  color: var(--muted-strong);
  font-size: 12px;
  font-weight: 600;
}
.sync-pill.synced { background: var(--green-soft); color: var(--green); }
.sync-pill.pending { background: var(--amber-soft); color: var(--amber); }
.sync-pill.syncing { background: var(--primary-soft); color: var(--primary-strong); }
.sync-pill.sync-error { background: var(--rose-soft); color: var(--rose); }
.sync-pill.local-only { background: #eef1ef; color: var(--muted-strong); }
.topbar h2 { margin-top: 4px; font-size: 24px; line-height: 1.1; }
.topbar p { margin-top: 6px; color: var(--muted); font-size: 14px; max-width: 720px; line-height: 1.6; }
.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 11px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: .08em;
  color: var(--muted);
}
.primary-tabs {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}
.primary-tab, .segment-tab, .btn, .icon-btn, .text-link, .chip-btn {
  border: 1px solid transparent;
  background: transparent;
  color: inherit;
  cursor: pointer;
}
.primary-tab {
  padding: 10px 15px;
  border-radius: 999px;
  background: rgba(248, 250, 248, 0.78);
  border-color: var(--line);
  color: var(--muted-strong);
  transition: .18s ease;
}
.primary-tab.active {
  background: var(--surface);
  border-color: rgba(63, 109, 104, 0.3);
  color: var(--primary-strong);
  box-shadow: inset 0 0 0 1px rgba(63, 109, 104, 0.08);
}
.icon-btn {
  width: 40px;
  height: 40px;
  border-radius: 12px;
  background: rgba(248, 250, 248, 0.86);
  border: 1px solid var(--line);
}
.mobile-toggle { display: none; }
.page {
  min-width: 0;
  padding: 24px;
}
.page-stack, .overview-stack { width: min(100%, var(--max-width)); margin: 0 auto; display: grid; gap: 20px; }
.surface-panel {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 22px;
  box-shadow: var(--shadow);
}
.compact-panel { padding: 18px; }
.emphasis-panel { background: linear-gradient(180deg, #f7faf8 0%, #f1f5f3 100%); }
.body-copy, .muted, .question-head span, .wrong-meta, .footer-note { color: var(--muted); line-height: 1.7; }
.auth-layer {
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 40;
}
.auth-layer.open {
  pointer-events: auto;
}
.auth-backdrop {
  position: absolute;
  inset: 0;
  background: rgba(26, 36, 41, 0.42);
}
.auth-modal {
  position: absolute;
  top: 50%;
  left: 50%;
  width: min(92vw, 520px);
  transform: translate(-50%, -50%);
  display: grid;
  gap: 18px;
  box-shadow: 0 24px 60px rgba(23, 35, 40, 0.16);
}
.auth-modal-head {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  align-items: flex-start;
}
.auth-stack {
  display: grid;
  gap: 14px;
}
.field-stack {
  display: grid;
  gap: 8px;
}
.field-label {
  color: var(--muted-strong);
  font-size: 13px;
  font-weight: 600;
}
.auth-info-card,
.generated-box {
  display: grid;
  gap: 10px;
  padding: 16px;
  border-radius: 12px;
  background: var(--surface-soft);
  border: 1px solid var(--line);
}
.auth-info-row {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  align-items: center;
}
.auth-info-row span {
  color: var(--muted);
  font-size: 13px;
}
.auth-info-row strong {
  color: var(--ink);
  font-size: 14px;
}
.danger-box {
  display: grid;
  gap: 10px;
  padding: 16px;
  border-radius: 12px;
  background: #fbf4f5;
  border: 1px solid rgba(157, 97, 106, 0.2);
}
.section-heading {
  display: flex;
  justify-content: space-between;
  gap: 14px;
  align-items: center;
  margin-bottom: 16px;
}
.section-heading.align-start { align-items: flex-start; }
.section-heading.spread { align-items: flex-start; }
.section-heading h3 { margin-top: 6px; font-size: 22px; line-height: 1.24; }
.soft-badge, .tiny-pill, .status-pill, .info-pill {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border-radius: 999px;
  font-size: 12px;
  font-weight: 600;
}
.soft-badge { padding: 7px 10px; background: var(--primary-soft); color: var(--primary-strong); }
.tiny-pill { padding: 5px 8px; background: #e7edea; color: var(--muted-strong); }
.info-pill { padding: 8px 12px; background: #e6efeb; color: var(--primary-strong); }
.status-pill { padding: 7px 10px; background: #e8eeeb; color: var(--muted-strong); }
.status-pill.mastered { background: var(--green-soft); color: var(--green); }
.status-pill.review { background: var(--amber-soft); color: var(--amber); }

.overview-hero {
  display: grid;
  grid-template-columns: minmax(0, 1.45fr) minmax(280px, .85fr);
  gap: 22px;
  align-items: stretch;
  background:
    radial-gradient(circle at top left, rgba(122, 171, 160, 0.12) 0%, rgba(122, 171, 160, 0) 34%),
    linear-gradient(135deg, #fbfdfc 0%, #f4f8f6 50%, #eef4f1 100%);
  border: 1px solid rgba(191, 204, 198, 0.86);
  border-radius: 20px;
  padding: 28px;
  box-shadow: 0 10px 26px rgba(36, 50, 58, 0.05);
  position: relative;
  overflow: hidden;
}
.hero-title {
  margin-top: 10px;
  font-size: 36px;
  line-height: 1.12;
  max-width: 11ch;
  letter-spacing: 0;
}
.hero-copy {
  display: grid;
  align-content: start;
  gap: 16px;
}
.hero-copy .body-copy { max-width: 56ch; }
.hero-actions { margin-top: 4px; }
.hero-side { display: flex; align-items: stretch; }
.hero-note {
  width: 100%;
  display: grid;
  gap: 14px;
  align-content: start;
  background: rgba(252, 253, 252, 0.92);
  border: 1px solid rgba(191, 204, 198, 0.86);
  border-radius: 16px;
  box-shadow: 0 8px 20px rgba(36, 50, 58, 0.04);
}
.hero-note-head {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 12px;
}
.hero-note-head h4 {
  margin-top: 6px;
  font-size: 18px;
  line-height: 1.35;
}
.hero-status-card .metric-card strong {
  font-size: 22px;
}
.hero-status-card .metric-grid.single-column {
  grid-template-columns: repeat(2, minmax(0, 1fr));
}
.hero-status-card .metric-card small {
  color: var(--muted);
  font-size: 12px;
  line-height: 1.5;
}
.metric-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 12px; }
.metric-grid.single-column { grid-template-columns: 1fr; width: 100%; }
.metric-card {
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 14px;
  background: rgba(245, 248, 246, 0.95);
  display: grid;
  gap: 6px;
}
.metric-card span { color: var(--muted); font-size: 12px; }
.metric-card strong { font-size: 24px; font-weight: 700; }
.hero-meta-grid { display: grid; grid-template-columns: repeat(3, minmax(120px, 1fr)); gap: 12px; }
.overview-metrics-panel,
.overview-next-panel {
  display: grid;
  gap: 16px;
}
.overview-metrics-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 14px;
}
.overview-number-card {
  display: grid;
  gap: 8px;
  padding: 18px;
  border-radius: 14px;
  border: 1px solid rgba(197, 208, 202, 0.82);
  background: rgba(250, 252, 250, 0.92);
}
.overview-number-card span {
  color: var(--muted);
  font-size: 12px;
}
.overview-number-card strong {
  font-size: 28px;
  line-height: 1.1;
  color: var(--ink);
}
.overview-number-card small {
  color: var(--muted-strong);
  line-height: 1.5;
}
.overview-next-layout {
  display: grid;
  grid-template-columns: minmax(0, 1.3fr) minmax(260px, .7fr);
  gap: 18px;
}
.overview-chapter-entry {
  display: grid;
  gap: 16px;
}
.overview-entry-row {
  display: grid;
  grid-template-columns: minmax(0, 1.2fr) auto;
  gap: 18px;
  align-items: center;
  padding: 18px;
  border: 1px solid rgba(197, 208, 202, 0.8);
  border-radius: 14px;
  background: rgba(250, 252, 250, 0.9);
}
.overview-entry-copy {
  display: grid;
  gap: 8px;
}
.overview-entry-copy strong {
  font-size: 18px;
  color: var(--ink);
}
.overview-entry-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  justify-content: flex-end;
}
.next-main-card,
.next-side-card {
  border: 1px solid rgba(197, 208, 202, 0.8);
  border-radius: 14px;
  background: rgba(250, 252, 250, 0.9);
  padding: 18px;
}
.next-main-card {
  display: grid;
  gap: 14px;
}
.next-links {
  display: flex;
  flex-wrap: wrap;
  gap: 14px;
}
.next-side-card {
  display: grid;
  gap: 14px;
  align-content: start;
}
.mini-wrong-row {
  display: grid;
  gap: 4px;
  padding: 12px 0;
  border-bottom: 1px solid rgba(197, 208, 202, 0.72);
}
.mini-wrong-row:last-of-type {
  border-bottom: 0;
  padding-bottom: 0;
}
.mini-wrong-row strong {
  font-size: 14px;
}
.mini-wrong-row span {
  color: var(--muted-strong);
  font-size: 13px;
  line-height: 1.5;
}
.mini-wrong-row.empty strong {
  color: var(--ink);
}
/* ── Wrongbook per-option explanation ── */
.wrongbook-options {
  list-style: none;
  padding-left: 0;
  display: grid;
  gap: 10px;
}
.wrongbook-option {
  padding: 14px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--line);
  background: var(--surface);
  border-left: 4px solid var(--line-strong);
}
.wrongbook-option.is-user {
  background: #fef0f2;
  border-left: 5px solid #d94f5c;
  box-shadow: inset 0 0 0 1px rgba(217, 79, 92, 0.12);
}
.wrongbook-option.is-correct {
  background: var(--green-soft);
  border-left: 5px solid var(--green);
}
.wrongbook-option.is-both {
  background: var(--green-soft);
  border-left: 5px solid var(--green);
}
.wrongbook-option-row {
  display: flex;
  align-items: center;
  gap: 10px;
}
.wrongbook-option-label {
  font-family: monospace;
  font-weight: 700;
  font-size: 14px;
  min-width: 22px;
  color: var(--ink);
}
.wrongbook-option.is-user .wrongbook-option-label {
  color: #c03b46;
}
.wrongbook-option-text {
  flex: 1;
  font-size: 14px;
  color: var(--ink);
}
.wrongbook-option.is-user .wrongbook-option-text {
  color: #a03842;
}
.wrongbook-tag {
  display: inline-flex;
  align-items: center;
  padding: 3px 10px;
  border-radius: 999px;
  font-size: 12px;
  font-weight: 600;
  flex-shrink: 0;
}
.wrongbook-tag.tag-user {
  background: #fef0f2;
  color: #c03b46;
  border: 1px solid #e8a0a6;
  font-weight: 700;
}
.wrongbook-tag.tag-correct {
  background: var(--green-soft);
  color: var(--green);
  border: 1px solid var(--green);
}
.wrongbook-option-explain {
  margin: 8px 0 0 32px;
  padding: 8px 12px;
  font-size: 13px;
  color: var(--muted);
  line-height: 1.6;
  border-left: 3px solid var(--line);
  background: var(--surface-alt);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
}
/* ── Wrongbook answer bar (judge/fill questions without options) ── */
.wrongbook-answer-bar {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 12px 14px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--line);
  background: var(--surface);
  flex-wrap: wrap;
}
.wrongbook-answer-label {
  font-size: 13px;
  color: var(--muted);
}
.wrongbook-answer-val {
  font-size: 15px;
  padding: 3px 12px;
  border-radius: 999px;
  font-weight: 700;
}
.wrongbook-answer-val.is-user {
  background: #fef0f2;
  color: #c03b46;
  border: 1px solid #e8a0a6;
}
.wrongbook-answer-val.is-correct {
  background: var(--green-soft);
  color: var(--green);
  border: 1px solid var(--green);
}
/* ── Fallback notice when userAnswer doesn't match any option label ── */
.wrongbook-user-notice {
  margin: 0 0 6px 0;
  padding: 6px 12px;
  font-size: 13px;
  color: #c03b46;
  background: #fef0f2;
  border-radius: var(--radius-sm);
  border: 1px solid #e8a0a6;
}
.next-side-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}
.workspace-grid { display: grid; grid-template-columns: minmax(0, 1.35fr) minmax(280px, .85fr); gap: 18px; align-items: start; }
.overview-main, .overview-side { display: grid; gap: 18px; }
.overview-stat-list {
  display: grid;
  gap: 12px;
}
.overview-stat-row {
  display: flex;
  justify-content: space-between;
  gap: 14px;
  align-items: center;
  padding: 12px 0;
  border-bottom: 1px solid rgba(197, 208, 202, 0.75);
}
.overview-stat-row:last-child { border-bottom: 0; padding-bottom: 0; }
.overview-stat-row:first-child { padding-top: 0; }
.overview-stat-row span {
  color: var(--muted);
  font-size: 13px;
}
.overview-stat-row strong {
  font-size: 15px;
  color: var(--ink);
}
.wrong-grid, .chapter-overview-grid, .guide-grid, .summary-board { display: grid; gap: 18px; }
.wrong-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.chapter-overview-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.guide-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.summary-board { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.summary-column h4 { margin-bottom: 10px; font-size: 15px; }
.chapter-overview-card, .wrong-card, .dense-row, .simulator-card, .quiz-card, .wrong-item, .point-card {
  border: 1px solid var(--line);
  border-radius: 12px;
  background: var(--surface);
}
.chapter-overview-card, .wrong-card, .wrong-item, .simulator-card, .quiz-card { padding: 16px; }
.chapter-card-head, .simulator-card-head, .point-card-head, .question-head { display: grid; gap: 8px; }
.chapter-card-head { display: flex; justify-content: space-between; gap: 16px; align-items: flex-start; }
.chapter-overview-card {
  display: grid;
  gap: 12px;
  padding: 18px;
}
.chapter-overview-card h4 { margin-top: 8px; font-size: 18px; }
.chapter-card-summary {
  margin-top: 8px;
  color: var(--muted);
  line-height: 1.6;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}
.chapter-card-progress-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 12px;
}
.chapter-card-progress-row span {
  color: var(--muted);
  font-size: 13px;
}
.chapter-card-progress-row strong {
  font-size: 15px;
}
.chapter-card-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}
.chapter-card-meta.secondary span {
  padding: 5px 9px;
  background: #f1f5f3;
  color: var(--muted-strong);
}
.chapter-card-meta span {
  display: inline-flex;
  align-items: center;
  padding: 6px 10px;
  border-radius: 999px;
  background: var(--surface-alt);
  color: var(--muted-strong);
  font-size: 12px;
}
.card-actions, .action-row, .point-actions { display: flex; gap: 10px; flex-wrap: wrap; }
.action-row.small { gap: 8px; }
.text-link {
  padding: 0;
  color: var(--primary-strong);
  font-weight: 600;
}
.progress-bar, .mini-progress {
  height: 8px;
  border-radius: 999px;
  background: #dde5e0;
  overflow: hidden;
}
.progress-bar > span, .mini-progress span {
  display: block;
  height: 100%;
  border-radius: inherit;
  background: linear-gradient(90deg, #8db1a7, #466d67);
}
.plain-list { display: grid; gap: 8px; color: var(--muted-strong); }
.pill-list { display: flex; gap: 10px; flex-wrap: wrap; }
.featured-item span, .dense-row span { color: var(--muted); font-size: 13px; }
.dense-row {
  width: 100%;
  text-align: left;
  padding: 14px;
  display: flex;
  justify-content: space-between;
  gap: 12px;
  cursor: pointer;
}
.dense-row em { font-style: normal; color: var(--primary-strong); font-weight: 700; }
.dense-row > div { display: grid; gap: 4px; }
.chapter-stack .section-heading h3, .training-stack .section-heading h3 { font-size: 22px; }
.compact-heading {
  margin-bottom: 14px;
}
.chapter-hero {
  background: linear-gradient(180deg, #f7faf8 0%, #eff4f1 100%);
}
.chapter-hero-layout {
  display: grid;
  grid-template-columns: minmax(0, 1.35fr) minmax(280px, .85fr);
  gap: 20px;
  align-items: start;
}
.chapter-hero-copy {
  display: grid;
  gap: 14px;
}
.chapter-hero-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}
.chapter-hero-tags span {
  display: inline-flex;
  align-items: center;
  padding: 7px 11px;
  border-radius: 999px;
  background: rgba(232, 238, 235, 0.95);
  color: var(--muted-strong);
  font-size: 12px;
}
.chapter-hero-metrics {
  align-self: stretch;
}
.chapter-guide-card {
  display: grid;
  align-content: start;
}
.section-head-actions {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
}
.section-block {
  padding: 24px;
  border-radius: 16px;
  background: linear-gradient(180deg, #fafcfb 0%, #f4f7f5 100%);
}
.section-block + .section-block {
  margin-top: 4px;
}
.section-overview-stack,
.section-mode-shell {
  display: grid;
  gap: 18px;
}
.section-overview-card {
  display: grid;
  gap: 16px;
}
.section-mode-nav {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  align-items: center;
}
.section-mode-switch {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  justify-content: flex-end;
}
.training-shell {
  display: grid;
  gap: 18px;
  background: linear-gradient(180deg, #f8faf8 0%, #f3f6f4 100%);
}
.training-shell-head {
  display: grid;
  grid-template-columns: minmax(0, 1.45fr) minmax(260px, .75fr);
  gap: 18px;
  align-items: start;
}
.training-status-card {
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 13px 14px;
  background: rgba(242, 245, 243, 0.94);
  display: grid;
  gap: 6px;
}
.training-status-card h4 {
  font-size: 16px;
  line-height: 1.35;
}
.training-tabs { margin-top: 12px; }
.training-panel {
  min-width: 0;
}
.training-panel-sheet {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 20px;
  box-shadow: 0 8px 18px rgba(36, 50, 58, 0.03);
}
.training-panel-head {
  margin-bottom: 18px;
}
.test-sheet {
  background: linear-gradient(180deg, #fbfcfb 0%, #f6f8f7 100%);
}
.point-list {
  gap: 16px;
}
.point-card {
  padding: 0;
  overflow: hidden;
  background: #fcfdfc;
  border-radius: 16px;
  box-shadow: 0 6px 16px rgba(36, 50, 58, 0.035);
}
.point-card summary {
  list-style: none;
  cursor: pointer;
  display: grid;
  gap: 16px;
  padding: 20px;
}
.point-card summary::-webkit-details-marker { display: none; }
.point-card-head {
  grid-template-columns: minmax(0, 1fr) auto;
  align-items: start;
}
.point-label-row {
  display: flex;
  align-items: center;
  gap: 10px;
}
.point-index {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 32px;
  height: 32px;
  padding: 0 10px;
  border-radius: 999px;
  background: linear-gradient(180deg, #eff5f2 0%, #e1ebe6 100%);
  color: var(--primary-strong);
  font-size: 12px;
  font-weight: 700;
}
.point-card-head strong {
  font-size: 18px;
  line-height: 1.35;
}
.point-conclusion {
  padding: 16px 18px;
  border-radius: 14px;
  background: linear-gradient(180deg, #e8f0ec 0%, #eef4f1 100%);
  color: var(--primary-strong);
  font-weight: 600;
  line-height: 1.6;
}
.point-excerpt {
  display: grid;
  gap: 6px;
  padding: 2px 2px 0;
}
.point-excerpt span, .detail-label, .field-label {
  font-size: 12px;
  font-weight: 700;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: .06em;
}
.point-excerpt p { color: var(--muted-strong); line-height: 1.7; }
.point-hint-row {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  color: var(--muted);
  font-size: 13px;
  padding-top: 2px;
  border-top: 1px dashed rgba(197, 208, 202, 0.9);
}
.point-detail-wrap {
  border-top: 1px solid var(--line);
  padding: 0 20px 20px;
  display: grid;
  gap: 16px;
  background: linear-gradient(180deg, rgba(245, 248, 246, 0.95) 0%, rgba(249, 251, 250, 0.95) 100%);
}
.point-detail-block {
  padding-top: 18px;
  border-top: 4px solid transparent;
}
.point-body { margin-top: 8px; line-height: 1.85; color: var(--ink); }
.point-meta-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 14px; }
.point-tip, .point-compare {
  padding: 16px;
  border-radius: 12px;
  background: var(--surface-alt);
}
.point-tip p { margin-top: 8px; color: #8b5b18; line-height: 1.7; }
.svg-box {
  padding: 14px;
  border-radius: 12px;
  background: linear-gradient(180deg, #f7faf8 0%, #eef4f1 100%);
  border: 1px solid rgba(183, 198, 190, 0.95);
  overflow: auto;
}
.svg-box svg {
  width: 100%;
  height: auto;
  display: block;
  min-width: 540px;
}
.select, .input {
  width: 100%;
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 12px 13px;
  background: #f9fbf9;
  color: var(--ink);
}
.toolbar-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 16px; }
.segment-tabs {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 16px;
}
.segment-tab {
  padding: 10px 14px;
  border-radius: 999px;
  border: 1px solid var(--line);
  background: var(--surface-soft);
  color: var(--muted-strong);
}
.segment-tab.active {
  background: var(--primary-soft);
  border-color: rgba(63, 109, 104, 0.18);
  color: var(--primary-strong);
}
.btn {
  padding: 11px 15px;
  border-radius: 12px;
  border: 1px solid var(--line);
  background: #f8faf8;
  color: var(--ink);
  transition: .18s ease;
}
.btn:hover, .segment-tab:hover, .primary-tab:hover, .simulator-card:hover, .dense-row:hover, .chapter-link:hover { transform: translateY(-1px); }
.btn.primary {
  background: var(--primary);
  border-color: var(--primary);
  color: #fff;
}
.btn.subtle {
  background: #eef3f0;
  border-color: var(--line);
  color: var(--muted-strong);
}
.btn.success {
  background: var(--green-soft);
  border-color: transparent;
  color: var(--green);
}
.btn.danger {
  background: var(--rose-soft);
  border-color: rgba(157, 97, 106, 0.22);
  color: var(--rose);
}
.btn.active { outline: 2px solid rgba(63, 109, 104, 0.12); }
.btn.tiny { padding: 9px 12px; font-size: 13px; }
.chip-btn {
  padding: 9px 12px;
  border-radius: 999px;
  background: #e5efea;
  color: var(--primary-strong);
}
.quiz-flow-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}
.quiz-flow-progress {
  display: grid;
  gap: 4px;
}
.quiz-flow-progress strong {
  font-size: 18px;
  line-height: 1.2;
}
.quiz-flow-progress small {
  font-size: 12px;
  color: var(--muted);
}
.quiz-list { display: grid; gap: 14px; }
.quiz-card.correct { border-color: rgba(63, 128, 103, 0.28); background: #f4fbf7; }
.quiz-card.wrong { border-color: rgba(157, 97, 106, 0.22); background: #fbf5f6; }
.option-list { display: grid; gap: 10px; margin-top: 14px; }
.option-btn {
  width: 100%;
  text-align: left;
  border: 1px solid var(--line);
  background: #fbfcfb;
  color: var(--ink);
  border-radius: 12px;
  padding: 12px 14px;
  cursor: pointer;
}
.option-btn.selected { border-color: rgba(63, 109, 104, 0.26); background: #eff5f2; }
.option-btn.correct { border-color: rgba(45, 143, 111, 0.32); background: var(--green-soft); }
.option-btn.wrong { border-color: rgba(187, 90, 104, 0.28); background: var(--rose-soft); }
.btn:disabled, .option-btn:disabled {
  opacity: 0.48;
  cursor: not-allowed;
  transform: none;
}
.feedback {
  margin-top: 12px;
  padding: 12px 14px;
  border-radius: 12px;
  line-height: 1.7;
}
.feedback.correct { background: var(--green-soft); color: var(--green); }
.feedback.wrong { background: var(--rose-soft); color: var(--rose); }
/* ── Option flag button ── */
.option-row {
  display: flex;
  gap: 8px;
  align-items: stretch;
}
.option-row .option-btn {
  flex: 1;
}
.option-flag-btn {
  flex-shrink: 0;
  width: 36px;
  border: 1px solid var(--line);
  background: #fbfcfb;
  color: var(--muted);
  border-radius: 10px;
  cursor: pointer;
  font-size: 15px;
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.15s;
}
.option-flag-btn:hover {
  border-color: var(--amber);
  color: var(--amber);
  background: #fffaf0;
}
.option-flag-btn.flagged {
  background: #fff7ed;
  border-color: var(--amber);
  color: var(--amber);
  box-shadow: inset 0 0 0 1px rgba(217, 150, 49, 0.15);
}
/* ── Guessed row ── */
.guessed-row {
  margin-top: 8px;
  text-align: right;
}
.guessed-row .btn {
  font-size: 12px;
  opacity: 0.65;
}
.guessed-row .btn:hover {
  opacity: 1;
}
/* ── Review list ── */
.review-guessed-banner {
  margin: 0 0 10px 0;
  padding: 6px 12px;
  font-size: 13px;
  font-weight: 600;
  color: #b85c10;
  background: #fff8f0;
  border-left: 4px solid var(--amber);
  border-radius: 6px;
}
.wrongbook-option.review-flagged {
  background: #fff8f0;
  border-left: 5px solid var(--amber);
  box-shadow: inset 0 0 0 1px rgba(217, 150, 49, 0.12);
}
.wrongbook-option.review-flagged .wrongbook-option-label {
  color: #b85c10;
}
.wrongbook-option.review-flagged .wrongbook-option-text {
  color: #8b6914;
}
.wrongbook-tag.review-tag {
  background: #fff8f0;
  color: #b85c10;
  border: 1px solid #e8c878;
  font-weight: 700;
}
.score-box {
  margin-top: 18px;
  display: flex;
  justify-content: space-between;
  gap: 12px;
  align-items: center;
  padding: 16px;
  border-radius: 12px;
  background: var(--surface-alt);
}
.score-box strong { font-size: 30px; }
.simulator-layout {
  display: grid;
  grid-template-columns: 320px minmax(0, 1fr);
  gap: 18px;
  align-items: start;
}
.simulator-rail {
  position: sticky;
  top: 110px;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: var(--surface);
  padding: 18px;
  box-shadow: 0 8px 18px rgba(36, 50, 58, 0.03);
}
.simulator-group-block { display: grid; gap: 10px; }
.simulator-group-block h4 { font-size: 14px; color: var(--muted-strong); }
.simulator-card {
  width: 100%;
  text-align: left;
  cursor: pointer;
}
.simulator-card span { display: block; margin-top: 8px; font-size: 13px; color: var(--muted); line-height: 1.6; }
.simulator-card.active { border-color: var(--primary); background: #f1f6f4; }
.simulator-main { display: grid; gap: 18px; }
.simulator-context {
  border: 1px solid var(--line);
  border-radius: 14px;
  background: linear-gradient(180deg, #f8faf8 0%, #f2f5f3 100%);
  padding: 18px;
}
.simulator-stage-host .sim-stage { display: grid; gap: 18px; }
.simulator-stage-host .sim-help { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 18px; }
.simulator-stage-host canvas { width: 100%; max-width: 100%; border-radius: 14px; background: #0f172a; }
.empty-state {
  border: 1px dashed var(--line-strong);
  border-radius: 14px;
  padding: 28px 18px;
  text-align: center;
  color: var(--muted);
  background: rgba(244, 247, 245, 0.8);
}
.error-box {
  margin-top: 14px;
  padding: 14px;
  border-radius: 12px;
  background: #163043;
  color: #e7f1f6;
  overflow: auto;
  white-space: pre-wrap;
}

.dual-track-grid,
.chapter-guide-grid,
.point-lane-list,
.checklist-grid {
  display: grid;
  gap: 16px;
}

.dual-track-grid {
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.track-card {
  display: grid;
  gap: 12px;
  padding: 18px;
  border-radius: 18px;
  border: 1px solid rgba(183, 198, 190, 0.95);
  background: rgba(255, 255, 255, 0.62);
}

.track-card.accent {
  background: linear-gradient(180deg, rgba(226, 240, 235, 0.94) 0%, rgba(241, 248, 244, 0.92) 100%);
  border-color: rgba(111, 149, 136, 0.5);
}

.track-card h4 {
  font-size: 20px;
  line-height: 1.3;
}

.track-meta {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}

.track-meta span,
.must-topic-chip,
.checklist-item {
  font-size: 13px;
}

.track-meta span {
  display: inline-flex;
  align-items: center;
  padding: 7px 11px;
  border-radius: 999px;
  background: rgba(240, 245, 242, 0.9);
  color: var(--muted-strong);
}

.btn.subtle.strong {
  background: #dfece7;
  color: var(--primary-strong);
  border-color: rgba(111, 149, 136, 0.35);
}

.chapter-guide-shell {
  padding: 18px;
  background: linear-gradient(180deg, #f8faf8 0%, #f2f6f4 100%);
}

.chapter-guide-grid {
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.chapter-guide-card {
  padding: 18px;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: rgba(255, 255, 255, 0.72);
}

.chapter-guide-card.accent {
  background: linear-gradient(180deg, #edf5f1 0%, #f8fbf9 100%);
}

.must-topic-list {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}

.must-topic-chip {
  border: 1px solid rgba(111, 149, 136, 0.24);
  background: #edf4f1;
  color: var(--primary-strong);
  border-radius: 999px;
  padding: 9px 12px;
  cursor: pointer;
}

.must-topic-chip.compact {
  padding: 7px 10px;
  background: #f3f6f4;
}

.section-quickstart {
  display: grid;
  gap: 10px;
  padding: 14px 16px;
  border-radius: 14px;
  background: #f2f6f4;
  border: 1px solid var(--line);
  margin-bottom: 18px;
}

.section-snapshot-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 10px;
}

.section-snapshot-card {
  display: grid;
  gap: 4px;
  padding: 12px 14px;
  border-radius: 12px;
  border: 1px solid var(--line);
  background: rgba(255, 255, 255, 0.86);
}

.section-snapshot-card span,
.teacher-paper-sequence span {
  font-size: 12px;
  color: var(--muted);
}

.section-snapshot-card strong {
  font-size: 15px;
  color: var(--primary-strong);
}

.section-snapshot-card small {
  line-height: 1.5;
  color: var(--muted-strong);
}

.section-snapshot-card.essential {
  background: #f6faf8;
}

.section-snapshot-card.standard {
  background: #fbfcfb;
}

.section-snapshot-card.review {
  background: #faf6f0;
}

.point-lane-head {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  align-items: baseline;
  margin-bottom: 12px;
}

.point-lane-head strong {
  font-size: 15px;
}

.point-lane-head span {
  color: var(--muted);
  font-size: 13px;
}

.point-lane {
  padding: 16px;
  border-radius: 16px;
  border: 1px solid var(--line);
  background: #f9fbfa;
}

.lane-essential {
  background: linear-gradient(180deg, #f6faf8 0%, #f1f7f4 100%);
}

.lane-standard {
  background: linear-gradient(180deg, #fbfcfb 0%, #f5f8f7 100%);
}

.lane-advanced {
  background: linear-gradient(180deg, #fcfaf7 0%, #f8f2e9 100%);
}

.checklist-panel {
  margin-top: 18px;
  padding-top: 18px;
  border-top: 1px solid var(--line);
  display: grid;
  gap: 12px;
}

.checklist-panel h4 {
  font-size: 15px;
}

.checklist-grid {
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.checklist-item {
  display: grid;
  gap: 4px;
  padding: 14px;
  border-radius: 12px;
  background: #f4f7f5;
  border: 1px solid var(--line);
}

.checklist-item.done {
  background: var(--green-soft);
  border-color: rgba(63, 128, 103, 0.2);
}

.checklist-item strong {
  color: var(--primary-strong);
}

.passline-sheet {
  background: linear-gradient(180deg, #f7fbf9 0%, #f1f6f3 100%);
}

.passline-summary-strip {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 12px;
  margin-bottom: 16px;
}

.passline-summary-strip > div {
  padding: 14px;
  border-radius: 12px;
  background: rgba(255, 255, 255, 0.72);
  border: 1px solid var(--line);
  display: grid;
  gap: 6px;
}

.passline-summary-strip span {
  color: var(--muted);
  font-size: 12px;
}

.passline-summary-strip strong {
  font-size: 20px;
}

.teacher-filter-shell {
  display: grid;
  gap: 16px;
}

.teacher-paper-shell {
  display: grid;
  gap: 14px;
  padding: 18px;
  border: 1px solid rgba(61, 117, 153, 0.14);
  border-radius: 18px;
  background: linear-gradient(180deg, rgba(250, 252, 255, 0.98) 0%, rgba(244, 248, 251, 0.98) 100%);
}

.teacher-paper-head {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  align-items: end;
}

.teacher-paper-head h4,
.teacher-active-paper-copy h4,
.teacher-quick-card h4 {
  font-size: 18px;
  margin: 6px 0 0;
}

.teacher-paper-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
}

.teacher-paper-sequence {
  display: grid;
  gap: 8px;
}

.teacher-sequence-row {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.teacher-sequence-row span {
  display: inline-flex;
  align-items: center;
  padding: 8px 12px;
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.82);
  border: 1px solid rgba(78, 107, 130, 0.1);
  color: var(--muted-strong);
  font-size: 13px;
}

.teacher-quick-card {
  border: 1px solid rgba(78, 107, 130, 0.12);
  border-radius: 16px;
  padding: 16px;
  background: #fff;
  text-align: left;
  display: grid;
  gap: 10px;
  box-shadow: 0 10px 28px rgba(29, 53, 74, 0.05);
}

.teacher-quick-card.active {
  border-color: rgba(61, 117, 153, 0.3);
  background: linear-gradient(180deg, #f8fbff 0%, #eef6fb 100%);
  box-shadow: 0 14px 32px rgba(46, 88, 120, 0.1);
}

.teacher-quick-card p {
  margin: 0;
  color: var(--muted);
  line-height: 1.6;
}

.teacher-quick-card-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}

.teacher-active-paper {
  display: grid;
  gap: 14px;
  padding: 18px;
}

.teacher-active-paper-copy {
  display: grid;
  gap: 6px;
}

.teacher-active-paper-copy p {
  margin: 0;
}

.teacher-active-paper-meta {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 12px;
}

.teacher-active-paper-meta > div {
  display: grid;
  gap: 4px;
  padding: 12px 14px;
  border-radius: 14px;
  background: rgba(255, 255, 255, 0.78);
  border: 1px solid rgba(78, 107, 130, 0.1);
}

.teacher-active-paper-meta span,
.teacher-question-meta span {
  color: var(--muted);
  font-size: 12px;
}

.teacher-active-paper-meta strong {
  font-size: 16px;
}

.teacher-selection-strip {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 10px;
}

.teacher-selection-strip > div {
  display: grid;
  gap: 4px;
  padding: 12px 14px;
  border-radius: 12px;
  background: rgba(255, 255, 255, 0.72);
  border: 1px solid rgba(78, 107, 130, 0.1);
}

.teacher-selection-strip span {
  color: var(--muted);
  font-size: 12px;
}

.teacher-selection-strip strong {
  font-size: 15px;
  color: var(--primary-strong);
}

.teacher-custom-shell {
  display: grid;
  gap: 12px;
}

.teacher-toolbar {
  align-items: end;
}

.teacher-focus-card {
  border-color: rgba(61, 117, 153, 0.22);
  background: linear-gradient(180deg, #fbfdff 0%, #f5f9fc 100%);
}

.teacher-sheet {
  display: grid;
  gap: 18px;
}

.teacher-question-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 8px;
}

.teacher-summary-strip {
  margin-bottom: 0;
}

.teacher-tag-row {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 10px;
}

.teacher-source-pills {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.teacher-source-pills .tiny-pill {
  background: #edf2ef;
}

.teacher-source-pills .tiny-pill.active {
  background: var(--primary-soft);
  color: var(--primary-strong);
}

.teacher-helper-note {
  padding: 14px 16px;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: rgba(243, 247, 245, 0.92);
}

.teacher-guide-card {
  border-style: dashed;
}

.teacher-empty-state {
  display: grid;
  gap: 12px;
}

.teacher-empty-state strong {
  font-size: 18px;
  color: var(--primary-strong);
}

.teacher-empty-state p {
  margin: 0;
}

@media (max-width: 1180px) {
  .workspace-grid, .overview-hero, .overview-next-layout, .overview-metrics-grid, .overview-entry-row, .guide-grid, .summary-board, .simulator-layout, .simulator-stage-host .sim-help, .wrong-grid, .overview-route, .route-grid, .chapter-hero-layout, .training-shell-head, .hero-band-grid, .dual-track-grid, .chapter-guide-grid, .checklist-grid, .passline-summary-strip, .chapter-node-head { grid-template-columns: 1fr; }
  .chapter-overview-grid { grid-template-columns: 1fr; }
  .hero-title { max-width: none; }
  .teacher-paper-grid, .teacher-active-paper-meta, .teacher-selection-strip, .section-snapshot-grid { grid-template-columns: 1fr; }
}

@media (max-width: 920px) {
  .app-shell.workspace-layout { grid-template-columns: 1fr; }
  .sidebar {
    position: fixed;
    inset: 0 auto 0 0;
    width: min(84vw, 320px);
    transform: translateX(-100%);
    transition: transform .22s ease;
    z-index: 30;
    box-shadow: 0 24px 40px rgba(23, 42, 58, 0.12);
  }
  .sidebar.open { transform: translateX(0); }
  .mobile-toggle { display: inline-grid; place-items: center; }
  .topbar { padding: 16px 18px; }
  .page { padding: 18px; }
  .toolbar-grid { grid-template-columns: 1fr; }
  .topbar-right { width: 100%; justify-content: flex-start; }
  .chapter-tree.compact { gap: 7px; }
  .chapter-link { padding: 8px 10px; }
  .section-link { padding: 7px 9px; }
}

@media (max-width: 640px) {
  .page { padding: 14px; }
  .topbar h2 { font-size: 21px; }
  .hero-title { font-size: 32px; }
  .overview-hero { padding: 22px; border-radius: 20px; }
  .topbar-inner { align-items: flex-start; }
  .primary-tabs { width: 100%; }
  .account-bar { width: 100%; }
  .hero-meta-grid, .metric-grid, .point-meta-grid, .overview-metrics-grid, .hero-status-card .metric-grid.single-column { grid-template-columns: 1fr; }
  .section-heading { flex-direction: column; align-items: flex-start; }
  .chapter-card-head { flex-direction: column; }
  .hero-note-head, .overview-stat-row { flex-direction: column; align-items: flex-start; }
  .score-box { flex-direction: column; align-items: flex-start; }
  .teacher-paper-head { flex-direction: column; align-items: flex-start; }
  .next-links, .next-side-actions, .overview-entry-actions, .section-mode-nav, .section-mode-switch, .quiz-flow-head { flex-direction: column; align-items: flex-start; }
  .chapter-tree.compact { gap: 6px; }
  .chapter-node { gap: 5px; }
  .chapter-node-head {
    grid-template-columns: minmax(0, 1fr) 28px;
    gap: 5px;
  }
  .chapter-link {
    padding: 8px 9px;
    border-radius: 9px;
  }
  .chapter-link strong,
  .section-link strong {
    font-size: 12px;
  }
  .chapter-link span,
  .section-link span {
    font-size: 11px;
    line-height: 1.32;
  }
  .chapter-link-meta {
    gap: 4px 8px;
    margin-top: 6px;
    font-size: 10px;
  }
  .chapter-expand-btn {
    width: 28px;
    height: 28px;
    min-height: 28px;
    border-radius: 8px;
    font-size: 10px;
  }
  .section-tree {
    gap: 5px;
    padding-left: 8px;
  }
  .section-link {
    padding: 7px 8px;
    border-radius: 8px;
  }
}