:root {
  color-scheme: light;
  --sidebar-width: 300px;
  --bg: #f5f5f5;
  --panel: #ffffff;
  --panel-soft: #f0f0f0;
  --border: #d7d7d7;
  --border-strong: #bdbdbd;
  --tree-guide: #9b9b9b;
  --text: #1f1f1f;
  --muted: #676767;
  --shadow: 0 12px 28px rgba(0, 0, 0, 0.05);
  --weak: #e6b85c;
  --hard: #d86f6f;
  --mastered: #78b886;
  --unmarked: #dddddd;
}

body.theme-dark {
  color-scheme: dark;
  --bg: #101010;
  --panel: #1a1a1a;
  --panel-soft: #262626;
  --border: #383838;
  --border-strong: #565656;
  --tree-guide: #666666;
  --text: #f0f0f0;
  --muted: #b5b5b5;
  --shadow: 0 12px 28px rgba(0, 0, 0, 0.35);
  --unmarked: #4e4e4e;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
  color: var(--text);
  background: linear-gradient(180deg, var(--panel) 0%, var(--bg) 100%);
}

button {
  font: inherit;
}

.layout {
  display: grid;
  grid-template-columns: var(--sidebar-width) 8px 1fr;
  min-height: 100vh;
}

.sidebar {
  position: sticky;
  top: 0;
  height: 100vh;
  display: flex;
  flex-direction: column;
  padding: 24px 18px;
  border-right: 1px solid var(--border);
  background: color-mix(in srgb, var(--panel) 92%, transparent);
}

.sidebar-resizer {
  position: sticky;
  top: 0;
  z-index: 25;
  width: 8px;
  height: 100vh;
  cursor: col-resize;
  background: transparent;
}

.sidebar-resizer::after {
  content: "";
  display: block;
  width: 1px;
  height: 100%;
  margin: 0 auto;
  background: transparent;
}

.sidebar-resizer:hover::after,
body.is-resizing-sidebar .sidebar-resizer::after {
  background: var(--border-strong);
}

body.is-resizing-sidebar {
  cursor: col-resize;
  user-select: none;
}

.sidebar-header h1,
.hero h2,
.board-header h3,
.question-title {
  margin: 0;
}

.sidebar-header p,
.hero-notes,
.save-tip,
.question-kicker,
.question-meta,
.state-text,
.save-text,
.tile-metrics,
.metric-label,
.daily-label,
.daily-value,
.tree-meta,
.chapter-note {
  color: var(--muted);
}

.tree {
  flex: 1;
  overflow: auto;
  padding-right: 6px;
}

.sidebar-home-entry {
  margin: 12px 0 4px;
}

.tree-home-button {
  background: var(--panel-soft);
  border-color: var(--border);
}

.tree-group {
  margin-top: 12px;
}

.tree-button,
.tree-leaf {
  width: 100%;
  display: flex;
  justify-content: space-between;
  align-items: center;
  border: 1px solid transparent;
  border-radius: 14px;
  background: transparent;
  padding: 10px 12px;
  color: var(--text);
  text-align: left;
  cursor: pointer;
}

.tree-left {
  min-width: 0;
  display: flex;
  flex-direction: column;
  gap: 6px;
  align-items: flex-start;
  flex: 1;
}

.tree-label {
  display: block;
}

.tree-mini-track {
  width: 100%;
  max-width: 96px;
  height: 4px;
  border-radius: 999px;
  background: #d9e5ef;
  overflow: hidden;
}

.tree-mini-fill {
  display: block;
  height: 100%;
  width: 0%;
  border-radius: 999px;
  background: #8ecbff;
}

.tree-button:hover,
.tree-leaf:hover,
.status-button:hover,
.answer-toggle:hover,
.icon-button:hover,
.image-original-toggle:hover {
  border-color: var(--border);
  background: var(--panel-soft);
}

.tree-button.active,
.tree-leaf.active {
  background: var(--panel-soft);
  border-color: var(--border-strong);
}

.tree-children {
  margin-left: 16px;
  padding-left: 8px;
  border-left: 1px dashed var(--tree-guide);
}

.tree-meta {
  font-size: 12px;
}

.sidebar-footer {
  padding-top: 14px;
  border-top: 1px solid var(--border);
}

.save-status {
  font-size: 14px;
  font-weight: 600;
}

.main {
  padding: 28px;
}

.topbar {
  position: sticky;
  top: 0;
  z-index: 20;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 16px;
  margin-bottom: 20px;
  padding: 12px 16px;
  border: 1px solid var(--border);
  border-radius: 18px;
  background: color-mix(in srgb, var(--panel) 92%, transparent);
  box-shadow: var(--shadow);
}

.topbar-title-group {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.topbar-title {
  font-weight: 700;
}

.topbar-subtitle {
  font-size: 13px;
  color: var(--muted);
}

.topbar-actions {
  display: flex;
  gap: 10px;
  align-items: center;
}

.color-filter-wrapper {
  position: relative;
}

.color-filter-wrapper.is-filtered .icon-button {
  border-color: var(--border-strong);
  background: var(--panel-soft);
}

.color-filter-popover {
  position: absolute;
  top: calc(100% + 10px);
  right: 0;
  z-index: 40;
  min-width: 220px;
  padding: 14px;
  border: 1px solid var(--border);
  border-radius: 18px;
  background: var(--panel);
  box-shadow: var(--shadow);
}

.color-filter-options {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 10px;
  margin-bottom: 14px;
}

.color-filter-option {
  display: flex;
  gap: 8px;
  align-items: center;
  color: var(--text);
  font-size: 14px;
}

.color-filter-actions {
  display: flex;
  justify-content: flex-end;
  gap: 8px;
}

.color-filter-actions .primary-button,
.color-filter-actions .secondary-button {
  padding: 7px 10px;
  font-size: 13px;
}

.topbar-progress {
  flex: 1;
  min-width: 180px;
  max-width: 420px;
}

.topbar-progress-text {
  display: flex;
  justify-content: space-between;
  gap: 10px;
  margin-bottom: 6px;
  font-size: 13px;
  color: var(--muted);
}

.topbar-progress-track {
  height: 10px;
  border-radius: 999px;
  background: var(--panel-soft);
  overflow: hidden;
}

.topbar-progress-fill {
  height: 100%;
  width: 0%;
  border-radius: 999px;
  background: #8ecbff;
  transition: width 0.18s ease;
}

.icon-button {
  width: 40px;
  height: 40px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--border);
  border-radius: 12px;
  background: var(--panel-soft);
  color: var(--text);
  cursor: pointer;
  padding: 0;
}

.icon-button svg {
  width: 18px;
  height: 18px;
  stroke: currentColor;
  fill: none;
  stroke-width: 1.9;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.status-button.active svg,
.action-button.active svg {
  stroke: currentColor;
}

.page-view.hidden {
  display: none;
}

.hero,
.summary-section,
.dashboard-filter-panel,
.overview-board,
.history-board,
.questions-section {
  margin-bottom: 24px;
}

.dashboard-filter-panel {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 18px;
}

.dashboard-color-filter {
  display: grid;
  grid-template-columns: repeat(5, max-content);
  gap: 12px;
}

.hero,
.overview-board,
.history-board,
.questions-section {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 24px;
  box-shadow: var(--shadow);
}

.hero {
  display: flex;
  justify-content: space-between;
  gap: 24px;
  padding: 24px;
}

.eyebrow {
  margin: 0 0 8px;
  font-size: 12px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--muted);
}

.hero-meta {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
  align-content: flex-start;
}

.meta-pill {
  padding: 10px 14px;
  border-radius: 999px;
  background: var(--panel-soft);
  border: 1px solid var(--border);
  white-space: nowrap;
}

.summary-section {
  display: grid;
  grid-template-columns: repeat(5, minmax(0, 1fr));
  gap: 16px;
}

.summary-card {
  padding: 18px;
  border-radius: 22px;
  background: var(--panel);
  border: 1px solid var(--border);
  box-shadow: var(--shadow);
}

.summary-value {
  font-size: 30px;
  font-weight: 700;
  margin: 8px 0 4px;
}

.summary-label,
.summary-subtext {
  color: var(--muted);
}

.board-header {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  align-items: center;
  padding: 24px 24px 0;
}

.legend {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
  font-size: 13px;
  color: var(--muted);
}

.legend-chip {
  width: 12px;
  height: 12px;
  display: inline-block;
  border-radius: 4px;
  margin-right: 6px;
  vertical-align: -1px;
}

.legend-chip.unmarked { background: var(--unmarked); }
.legend-chip.weak { background: var(--weak); }
.legend-chip.hard { background: var(--hard); }
.legend-chip.mastered { background: var(--mastered); }

.overview-panels {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 16px;
  padding: 24px;
}

.tile-panel {
  padding: 18px;
  border: 1px solid var(--border);
  border-radius: 22px;
  background: color-mix(in srgb, var(--panel) 94%, var(--bg));
}

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

.panel-title {
  margin: 0;
  font-size: 18px;
}

.tile-metrics {
  font-size: 13px;
}

.tile-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(11px, 1fr));
  gap: 4px;
}

.tile {
  width: 100%;
  aspect-ratio: 1;
  border-radius: 4px;
  background: var(--unmarked);
}

.tile.weak { background: var(--weak); }
.tile.hard { background: var(--hard); }
.tile.mastered { background: var(--mastered); }

.mini-metrics {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 10px;
  margin-top: 14px;
}

.metric-box {
  padding: 12px;
  border-radius: 14px;
  background: var(--panel-soft);
}

.metric-value {
  display: block;
  font-size: 20px;
  font-weight: 700;
}

.metric-label {
  font-size: 12px;
}

.daily-history {
  display: grid;
  gap: 10px;
  padding: 24px;
}

.daily-row {
  display: grid;
  grid-template-columns: 110px 1fr 50px;
  gap: 14px;
  align-items: center;
}

.daily-bar-track {
  height: 12px;
  border-radius: 999px;
  background: var(--panel-soft);
  overflow: hidden;
}

.daily-bar {
  height: 100%;
  border-radius: 999px;
  background: linear-gradient(90deg, #9e9e9e 0%, #727272 100%);
}

.question-list {
  padding: 0 24px 24px;
}

.chapter-block {
  padding-top: 24px;
}

.chapter-block + .chapter-block {
  border-top: 1px solid var(--border);
}

.chapter-header {
  margin-bottom: 18px;
}

.chapter-title {
  margin: 0;
  font-size: 26px;
}

.question-card {
  padding: 18px;
  border: 1px solid var(--border);
  border-radius: 24px;
  background: color-mix(in srgb, var(--panel) 94%, var(--bg));
  content-visibility: auto;
  contain: layout paint style;
  contain-intrinsic-size: 900px;
}

.question-card + .question-card {
  margin-top: 16px;
}

.question-header {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 14px;
}

.question-side-meta {
  display: flex;
  flex-direction: column;
  gap: 8px;
  align-items: flex-end;
}

.question-number-badge {
  padding: 10px 14px;
  border-radius: 14px;
  border: 1px solid var(--border);
  background: var(--panel-soft);
  font-weight: 700;
  color: var(--text);
}

.frame-color-dot {
  width: 28px;
  height: 28px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0;
  border-radius: 50%;
  border: 0;
  box-shadow: none;
  color: #fff;
  font-size: 11px;
  font-weight: 300;
  line-height: 1;
  text-shadow: 0 1px 2px rgba(0, 0, 0, 0.28);
}

.frame-color-dot.light-text {
  color: #111;
  text-shadow: none;
}

.image-frame {
  position: relative;
  width: min(100%, 960px);
  margin: 0 auto;
  border: 1px solid var(--border);
  border-radius: 19px;
  overflow: hidden;
  background: color-mix(in srgb, var(--panel) 90%, #ececec);
  min-height: 120px;
}

.image-original-toggle {
  position: absolute;
  top: 10px;
  right: 10px;
  z-index: 2;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: rgba(0, 0, 0, 0.62);
  color: #fff;
  padding: 8px 12px;
  cursor: pointer;
}

.question-kicker {
  margin: 0 0 6px;
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.question-image,
.answer-image {
  width: 100%;
  display: block;
  border-radius: 18px;
  border: 0;
  background: transparent;
  opacity: 0;
  transition: opacity 0.14s ease;
  visibility: hidden;
}

.study-image.is-ready {
  opacity: 1;
  visibility: visible;
}

body.theme-dark .study-image {
  filter: invert(1) hue-rotate(180deg);
}

body.theme-dark .study-image.show-original {
  filter: none;
}

body.theme-dark .image-frame {
  background: #161616;
}

.question-actions {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 14px;
  margin-top: 14px;
}

.question-actions-left,
.question-actions-right {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  align-items: center;
}

.action-button {
  min-width: 44px;
  height: 44px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0 12px;
}

.action-button svg {
  width: 18px;
  height: 18px;
  stroke: currentColor;
  fill: none;
  stroke-width: 1.9;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.status-button.weak svg {
  width: 22px;
  height: 22px;
  stroke-width: 2.25;
}

.status-button.hard svg,
.status-button.mastered svg {
  width: 20px;
  height: 20px;
}

.status-button,
.answer-toggle {
  border: 1px solid var(--border);
  border-radius: 999px;
  background: var(--panel-soft);
  padding: 10px 14px;
  cursor: pointer;
}

.status-button.active.weak { background: rgba(230, 184, 92, 0.18); border-color: var(--weak); }
.status-button.active.hard { background: rgba(216, 111, 111, 0.18); border-color: var(--hard); }
.status-button.active.mastered { background: rgba(120, 184, 134, 0.18); border-color: var(--mastered); }

.question-state-row {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  margin-top: 10px;
  font-size: 13px;
}

.note-preview {
  margin-top: 10px;
  padding: 12px 14px;
  border: 1px solid var(--border);
  border-radius: 14px;
  background: var(--panel-soft);
  color: var(--muted);
  white-space: pre-wrap;
  line-height: 1.5;
}

.answer-panel {
  margin-top: 14px;
}

.hidden {
  display: none;
}

.modal {
  position: fixed;
  inset: 0;
  z-index: 120;
}

.modal-backdrop {
  position: absolute;
  inset: 0;
  background: rgba(0, 0, 0, 0.48);
}

.modal-dialog {
  position: relative;
  z-index: 1;
  width: min(760px, calc(100vw - 32px));
  margin: 8vh auto 0;
  padding: 20px;
  border: 1px solid var(--border);
  border-radius: 24px;
  background: var(--panel);
  box-shadow: 0 22px 60px rgba(0, 0, 0, 0.28);
}

.modal-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 16px;
  margin-bottom: 16px;
}

.note-textarea {
  width: 100%;
  min-height: 260px;
  resize: vertical;
  padding: 14px 16px;
  border: 1px solid var(--border);
  border-radius: 16px;
  background: var(--panel-soft);
  color: var(--text);
  font: inherit;
}

.modal-actions {
  display: flex;
  justify-content: flex-end;
  gap: 12px;
  margin-top: 16px;
}

.primary-button,
.secondary-button {
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 10px 16px;
  cursor: pointer;
  font: inherit;
}

.primary-button {
  background: var(--text);
  color: var(--panel);
}

.secondary-button {
  background: var(--panel-soft);
  color: var(--text);
}

@media (max-width: 1100px) {
  .layout {
    grid-template-columns: 1fr;
  }

  .sidebar-resizer {
    display: none;
  }

  .sidebar {
    position: relative;
    height: auto;
    border-right: 0;
    border-bottom: 1px solid var(--border);
  }

  .summary-section,
  .overview-panels {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (max-width: 720px) {
  .main {
    padding: 16px;
  }

  .hero,
  .board-header,
  .question-list,
  .daily-history,
  .overview-panels {
    padding-left: 16px;
    padding-right: 16px;
  }

  .hero {
    flex-direction: column;
  }

  .topbar {
    flex-wrap: wrap;
    padding-left: 12px;
    padding-right: 12px;
  }

  .topbar-progress {
    order: 3;
    width: 100%;
    max-width: none;
  }

  .topbar-progress {
    order: 3;
    width: 100%;
    max-width: none;
  }

  .summary-section,
  .overview-panels {
    grid-template-columns: 1fr;
  }

  .question-actions {
    flex-direction: column;
    align-items: stretch;
  }

  .question-actions-left,
  .question-actions-right {
    justify-content: space-between;
  }

  .question-image,
  .answer-image,
  .image-frame {
    width: 100%;
  }

  .daily-row {
    grid-template-columns: 88px 1fr 40px;
  }
}