:root {
  --bg: #efe9dc;
  --bg-soft: #f8f5ef;
  --surface: rgba(255, 255, 255, 0.82);
  --surface-strong: #fffdfa;
  --border: rgba(53, 44, 31, 0.12);
  --text: #2e2924;
  --muted: #73685f;
  --navy: #17354e;
  --orange: #d76d3f;
  --orange-soft: #f3d9c9;
  --green: #3d765d;
  --shadow: 0 18px 40px rgba(64, 42, 18, 0.08);
  --radius-lg: 28px;
  --radius-md: 18px;
  --radius-sm: 12px;
  --font-display: "Georgia", "Times New Roman", serif;
  --font-body: "Microsoft YaHei UI", "Segoe UI", sans-serif;
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  min-height: 100%;
  background:
    radial-gradient(circle at top left, rgba(215, 109, 63, 0.18), transparent 28%),
    linear-gradient(180deg, #f7f1e8, #eee5d7);
  color: var(--text);
  font-family: var(--font-body);
}

button,
select {
  font: inherit;
}

.app-shell {
  display: grid;
  grid-template-columns: 300px minmax(0, 1fr);
  min-height: 100vh;
}

.sidebar {
  padding: 28px;
  background: rgba(23, 53, 78, 0.96);
  color: #f8f3eb;
  display: flex;
  flex-direction: column;
  gap: 24px;
  border-right: 1px solid rgba(255, 255, 255, 0.08);
}

.brand-block h1,
.topbar h2,
.panel h3,
.courseware-slide h3,
.courseware-slide h4,
.print-preview h3 {
  margin: 0;
  font-family: var(--font-display);
  letter-spacing: 0.02em;
}

.eyebrow {
  margin: 0 0 8px;
  font-size: 0.76rem;
  text-transform: uppercase;
  letter-spacing: 0.14em;
  color: rgba(115, 104, 95, 0.88);
}

.sidebar .eyebrow,
.sidebar p {
  color: rgba(248, 243, 235, 0.8);
}

.main-nav,
.card-stack,
.lesson-grid,
.compact-list {
  display: grid;
  gap: 12px;
}

.nav-link,
.secondary-button,
.slide-nav-button,
.practice-tab,
.card-type-button {
  border: none;
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: transform 140ms ease, background 140ms ease;
}

.nav-link {
  padding: 14px 16px;
  background: rgba(255, 255, 255, 0.08);
  text-align: left;
  color: #fff;
}

.nav-link.active,
.nav-link:hover {
  background: rgba(255, 255, 255, 0.18);
  transform: translateX(2px);
}

.sidebar-panel {
  margin-top: auto;
  padding: 18px;
  border-radius: var(--radius-md);
  background: rgba(255, 255, 255, 0.08);
}

.sidebar-shortcut {
  padding: 18px;
  border-radius: var(--radius-md);
  background: rgba(255, 255, 255, 0.08);
}

.sidebar-panel h2 {
  margin-top: 0;
  font-size: 1rem;
}

.sidebar-shortcut h2 {
  margin: 0 0 12px;
  font-size: 1rem;
}

.shortcut-link {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 100%;
  min-height: 44px;
  padding: 0 16px;
  border-radius: var(--radius-sm);
  background: rgba(255, 255, 255, 0.16);
  color: #fff;
  text-decoration: none;
}

.shortcut-link:hover {
  background: rgba(255, 255, 255, 0.24);
}

.sidebar-shortcut p {
  margin: 12px 0 0;
  color: rgba(248, 243, 235, 0.8);
  line-height: 1.7;
}

.compact-list {
  margin: 0;
  padding-left: 18px;
}

.content {
  padding: 28px;
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.topbar,
.topbar-actions,
.panel-header,
.courseware-toolbar,
.courseware-controls,
.courseware-slide-top,
.practice-toolbar {
  display: flex;
  gap: 12px;
  align-items: center;
}

.topbar,
.panel-header,
.courseware-toolbar,
.courseware-slide-top {
  justify-content: space-between;
}

.courseware-controls {
  justify-content: flex-end;
  flex-wrap: wrap;
}

.topbar-actions label {
  display: grid;
  gap: 8px;
  font-size: 0.92rem;
}

select {
  min-width: 220px;
  padding: 12px 14px;
  border-radius: 14px;
  border: 1px solid var(--border);
  background: rgba(255, 255, 255, 0.86);
}

.secondary-button {
  padding: 12px 16px;
  background: var(--orange-soft);
  color: #8f451f;
}

.view {
  display: none;
}

.view.active {
  display: block;
}

.section-shell,
.classroom-grid,
.cards-grid,
.courseware-tabs,
.courseware-slide-grid,
.practice-grid {
  display: grid;
  gap: 18px;
}

.split-shell {
  grid-template-columns: 360px minmax(0, 1fr);
}

#courseware-view .split-shell {
  grid-template-columns: 1fr;
}

#courseware-view .split-shell > .panel:first-child {
  display: none;
}

.classroom-grid {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.cards-grid {
  grid-template-columns: 300px minmax(0, 1fr);
}

.panel,
.courseware-panel,
.print-preview,
.practice-stage-panel {
  padding: 22px;
  border-radius: var(--radius-lg);
  background: var(--surface);
  border: 1px solid rgba(255, 255, 255, 0.55);
  box-shadow: var(--shadow);
  backdrop-filter: blur(12px);
}

.print-preview {
  display: grid;
  align-content: start;
}

.helper-text {
  color: var(--muted);
  font-size: 0.92rem;
}

.lesson-grid {
  grid-template-columns: 1fr;
}

.lesson-item,
.content-card,
.courseware-slide,
.practice-question,
.practice-plan,
.knowledge-card,
.outline-card {
  border-radius: var(--radius-md);
  border: 1px solid var(--border);
  background: var(--surface-strong);
  min-width: 0;
}

.lesson-item,
.outline-card {
  padding: 16px;
  cursor: pointer;
}

.lesson-item:hover,
.lesson-item.active,
.outline-card.active {
  border-color: rgba(215, 109, 63, 0.4);
  box-shadow: 0 10px 24px rgba(215, 109, 63, 0.1);
}

.lesson-phase {
  display: inline-flex;
  padding: 6px 10px;
  border-radius: 999px;
  background: #efe4d6;
  color: #8f4a24;
  font-size: 0.82rem;
}

.courseware-panel {
  display: grid;
  gap: 16px;
  min-width: 0;
  align-content: start;
}

.courseware-tabs {
  grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
}

.slide-tab {
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: rgba(255,255,255,0.78);
  color: var(--muted);
  cursor: pointer;
}

.slide-tab.active {
  background: var(--navy);
  border-color: var(--navy);
  color: #fff;
}

.courseware-slide {
  min-height: 0;
  padding: 28px;
  overflow: hidden;
  background:
    radial-gradient(circle at top right, rgba(215, 109, 63, 0.14), transparent 28%),
    linear-gradient(180deg, rgba(255,255,255,0.88), rgba(248,244,236,0.96));
}

.courseware-slide > * + * {
  margin-top: 18px;
}

.courseware-slide.cover {
  color: #fff7ef;
  background:
    radial-gradient(circle at top left, rgba(255,255,255,0.14), transparent 26%),
    linear-gradient(135deg, rgba(23, 53, 78, 0.98), rgba(215, 109, 63, 0.86));
}

.courseware-slide.cover p,
.courseware-slide.cover li,
.courseware-slide.cover h3,
.courseware-slide.cover h4 {
  color: inherit;
}

.courseware-step {
  display: inline-flex;
  padding: 7px 12px;
  border-radius: 999px;
  background: var(--orange-soft);
  color: #8f451f;
  font-weight: 700;
}

.courseware-slide-grid {
  grid-template-columns: repeat(2, minmax(0, 1fr));
  align-items: start;
}

.courseware-slide-top {
  margin-bottom: 18px;
}

.content-card,
.knowledge-card,
.practice-question,
.practice-plan {
  padding: 16px;
}

.content-card {
  background: rgba(255, 253, 250, 0.98);
}

.content-card h4,
.knowledge-card h4,
.practice-question h4,
.practice-plan h4,
.outline-card h4 {
  margin: 0 0 10px;
  font-size: 1rem;
  color: var(--navy);
}

.content-card p,
.knowledge-card p,
.practice-question p,
.practice-plan p,
.outline-card p,
.print-preview p {
  margin: 0 0 10px;
  line-height: 1.68;
  color: var(--muted);
}

.content-card p:last-child,
.knowledge-card p:last-child,
.practice-question p:last-child,
.practice-plan p:last-child {
  margin-bottom: 0;
}

.content-card ul,
.courseware-slide ul,
.courseware-slide ol,
.panel ul,
.print-preview ul {
  margin: 8px 0 0;
  padding-left: 18px;
  line-height: 1.7;
}

.practice-toolbar {
  margin-bottom: 18px;
}

.practice-tab {
  padding: 12px 18px;
  background: rgba(255,255,255,0.72);
  color: var(--muted);
  border: 1px solid var(--border);
}

.practice-tab.active {
  background: var(--navy);
  color: #fff;
  border-color: var(--navy);
}

.practice-grid {
  grid-template-columns: 1.15fr 0.85fr;
}

.knowledge-card-preview .knowledge-card,
.print-preview .knowledge-card {
  margin: 0 auto;
}

.card-type-button {
  padding: 14px 16px;
  text-align: left;
  border: 1px solid var(--border);
  background: rgba(255,255,255,0.76);
  color: var(--muted);
}

.card-type-button.active {
  background: var(--orange-soft);
  color: #8f451f;
  border-color: rgba(215, 109, 63, 0.34);
}

.knowledge-card {
  width: min(860px, 100%);
  margin: 0;
  padding: 26px;
  background: #fffdfa;
}

@media (max-width: 1200px) {
  .app-shell,
  .split-shell,
  .classroom-grid,
  .cards-grid,
  .practice-grid,
  .courseware-slide-grid {
    grid-template-columns: 1fr;
  }

  .sidebar {
    border-right: none;
    border-bottom: 1px solid rgba(255,255,255,0.08);
  }
}

@media (max-width: 760px) {
  .content,
  .sidebar {
    padding: 18px;
  }

  .topbar,
  .topbar-actions,
  .panel-header,
  .courseware-toolbar,
  .courseware-controls,
  .courseware-slide-top {
    flex-direction: column;
    align-items: stretch;
  }
}

@media print {
  .sidebar,
  .topbar,
  .main-nav,
  .courseware-tabs,
  .courseware-footer,
  .practice-toolbar,
  .compact-panel {
    display: none !important;
  }

  .app-shell,
  .content,
  .view,
  .view.active {
    display: block !important;
  }

  .courseware-slide,
  .print-preview,
  .knowledge-card {
    box-shadow: none;
    border: none;
    background: #fff !important;
  }

  .cards-grid,
  #knowledge-card-preview {
    display: block !important;
  }

  .knowledge-card {
    width: 100%;
    min-height: 250mm;
    padding: 18mm 16mm;
    page-break-after: always;
  }
}