:root {
  --bg: #f5f1e8;
  --paper: #fffdf8;
  --paper-strong: #f8f4ec;
  --ink: #201912;
  --muted: #746452;
  --line: #dfd4c4;
  --accent: #b44f2a;
  --accent-strong: #8f3d1d;
  --accent-soft: #f5dfd4;
  --green: #1f6a57;
  --green-soft: #d9eee7;
  --shadow: 0 20px 70px rgba(66, 47, 28, 0.12);
  --radius: 22px;
  --font-display: Georgia, "Times New Roman", serif;
  --font-body: "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
}

* {
  box-sizing: border-box;
}

[hidden] {
  display: none !important;
}

body {
  margin: 0;
  min-height: 100vh;
  color: var(--ink);
  font-family: var(--font-body);
  background:
    radial-gradient(circle at top left, rgba(180, 79, 42, 0.12), transparent 24%),
    radial-gradient(circle at 90% 12%, rgba(31, 106, 87, 0.12), transparent 18%),
    linear-gradient(180deg, #fbf8f2 0%, var(--bg) 100%);
}

.page-shell {
  width: min(1440px, calc(100% - 32px));
  margin: 0 auto;
  padding: 24px 0 36px;
}

.hero {
  display: block;
  margin-bottom: 20px;
}

.hero-subtitle {
  margin: 14px 0 0;
  max-width: 560px;
  font-size: 1rem;
  line-height: 1.6;
}

.mode-panel {
  margin-bottom: 20px;
}

.quick-jump-panel {
  margin-bottom: 20px;
}

body[data-browse-mode="formula"] .quick-jump-panel,
body[data-browse-mode="topic"] .quick-jump-panel {
  display: none;
}

.quick-jump-form {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 12px;
  align-items: end;
}

.quick-jump-field {
  margin: 0;
}

.quick-jump-field select {
  appearance: none;
  padding-right: 40px;
  background:
    linear-gradient(45deg, transparent 50%, var(--accent) 50%) calc(100% - 22px) calc(50% - 2px) / 8px 8px no-repeat,
    linear-gradient(135deg, var(--accent) 50%, transparent 50%) calc(100% - 16px) calc(50% - 2px) / 8px 8px no-repeat,
    #fff;
}

.quick-jump-status {
  margin-top: 12px;
}

.quick-jump-status.is-error {
  color: #a03d2a;
}

.mode-toggle {
  display: inline-flex;
  gap: 8px;
  padding: 6px;
  border-radius: 999px;
  border: 1px solid rgba(116, 100, 82, 0.12);
  background: rgba(255, 253, 248, 0.9);
  box-shadow: var(--shadow);
}

.mode-chip {
  border: 0;
  border-radius: 999px;
  padding: 10px 18px;
  background: transparent;
  color: var(--muted);
  font: inherit;
  font-weight: 700;
  cursor: pointer;
  transition: background 140ms ease, color 140ms ease, transform 140ms ease;
}

.mode-chip:hover {
  transform: translateY(-1px);
}

.mode-chip.active {
  background: var(--accent);
  color: #fff;
}

.hero-copy,
.hero-panel,
.panel {
  background: rgba(255, 253, 248, 0.9);
  border: 1px solid rgba(116, 100, 82, 0.12);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}

.hero-copy,
.hero-panel,
.panel {
  padding: 22px;
}

.hero-copy {
  position: relative;
}

.hero-logout {
  position: absolute;
  top: 22px;
  right: 22px;
}

.eyebrow {
  margin: 0 0 8px;
  text-transform: uppercase;
  letter-spacing: 0.14em;
  font-size: 0.74rem;
  font-weight: 700;
  color: var(--accent-strong);
}

.hero h1,
.panel h2,
.panel h3,
.panel h4 {
  margin: 0;
  font-family: var(--font-display);
}

.hero h1 {
  font-size: clamp(2rem, 3vw, 3.5rem);
  line-height: 1;
}

.muted {
  color: var(--muted);
}

.hero-actions,
.panel-head,
.group-head,
.stat-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}

.layout {
  display: grid;
  grid-template-columns: 340px minmax(0, 1fr);
  gap: 18px;
}

body[data-browse-mode="question"] .layout {
  grid-template-columns: 1fr;
}

.sidebar,
.content {
  min-width: 0;
}

.sidebar {
  display: flex;
  flex-direction: column;
  gap: 18px;
}

.content {
  display: grid;
  grid-template-columns: minmax(0, 1.85fr) minmax(300px, 340px);
  gap: 18px;
  align-items: start;
}

body[data-browse-mode="question"] .sidebar {
  display: none;
}

body[data-browse-mode="question"] .content {
  grid-template-columns: minmax(0, 1.5fr) minmax(320px, 0.7fr);
}

.formula-detail-panel {
  grid-column: 1;
}

.question-detail-panel {
  grid-column: 2;
  position: sticky;
  top: 24px;
  max-height: calc(100vh - 48px);
  overflow-y: auto;
}

body[data-browse-mode="question"] .question-detail-panel {
  position: static;
  top: auto;
  max-height: none;
}

.panel-grow {
  min-height: 560px;
}

.stack {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.field {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.field span,
.toggle-row span,
.stat-label {
  font-size: 0.85rem;
  color: var(--muted);
}

input,
select,
button {
  font: inherit;
}

input[type="text"],
input[type="password"],
input[type="search"],
select {
  width: 100%;
  border-radius: 14px;
  border: 1px solid var(--line);
  background: #fff;
  padding: 11px 12px;
  color: var(--ink);
}

.login-view {
  display: grid;
  min-height: 52vh;
  place-items: center;
}

.login-panel {
  width: min(440px, 100%);
}

.login-form {
  display: grid;
  gap: 14px;
  margin-top: 18px;
}

.button:disabled {
  opacity: 0.55;
  cursor: default;
}

.button {
  border-radius: 14px;
  border: 1px solid transparent;
  padding: 11px 14px;
  font-weight: 700;
  cursor: pointer;
  transition: transform 140ms ease, background 140ms ease, border-color 140ms ease;
}

.button:hover {
  transform: translateY(-1px);
}

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

.button-secondary {
  background: var(--paper-strong);
  border-color: var(--line);
  color: var(--ink);
}

.toggle-row {
  display: flex;
  align-items: center;
  gap: 10px;
}

.pill,
.badge {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 4px 10px;
  border-radius: 999px;
  font-size: 0.78rem;
  font-weight: 700;
}

.pill {
  background: var(--accent-soft);
  color: var(--accent-strong);
}

.pill-soft {
  background: var(--green-soft);
  color: var(--green);
}

.badge {
  background: rgba(31, 106, 87, 0.12);
  color: var(--green);
}

.formula-list,
.question-list {
  display: flex;
  gap: 10px;
  margin-top: 14px;
}

.formula-list {
  flex-direction: column;
  max-height: 428px;
  overflow-x: hidden;
  overflow-y: auto;
  scroll-snap-type: y proximity;
  padding-right: 4px;
}

.formula-list::-webkit-scrollbar {
  width: 10px;
}

.formula-list::-webkit-scrollbar-track {
  background: rgba(116, 100, 82, 0.08);
  border-radius: 999px;
}

.formula-list::-webkit-scrollbar-thumb {
  background: rgba(180, 79, 42, 0.35);
  border-radius: 999px;
}

.question-list {
  flex-direction: column;
  max-height: 428px;
  overflow-x: hidden;
  overflow-y: auto;
  scroll-snap-type: y proximity;
  padding-right: 4px;
}

.question-list::-webkit-scrollbar {
  width: 10px;
}

.question-list::-webkit-scrollbar-track {
  background: rgba(116, 100, 82, 0.08);
  border-radius: 999px;
}

.question-list::-webkit-scrollbar-thumb {
  background: rgba(31, 106, 87, 0.28);
  border-radius: 999px;
}

.formula-card,
.question-card {
  border: 1px solid rgba(116, 100, 82, 0.14);
  background: #fff;
  border-radius: 18px;
  padding: 14px;
  text-align: left;
  cursor: pointer;
  transition: transform 140ms ease, border-color 140ms ease, box-shadow 140ms ease;
}

.formula-card:hover,
.question-card:hover {
  transform: translateY(-1px);
  border-color: rgba(180, 79, 42, 0.45);
}

.formula-card.active,
.question-card.active {
  border-color: var(--accent);
  box-shadow: 0 12px 30px rgba(180, 79, 42, 0.12);
}

.formula-card {
  width: 100%;
  min-width: 0;
  display: flex;
  flex-direction: column;
  gap: 12px;
  scroll-snap-align: start;
}

.topic-card {
  padding: 16px;
}

.question-card {
  width: 100%;
  scroll-snap-align: start;
  min-height: 108px;
}

.formula-card-figure {
  border: 1px solid rgba(116, 100, 82, 0.14);
  border-radius: 16px;
  background:
    linear-gradient(180deg, rgba(180, 79, 42, 0.04), rgba(31, 106, 87, 0.04)),
    #fff;
  display: grid;
  place-items: center;
}

.formula-card-figure {
  min-height: 112px;
  overflow: hidden;
}

.formula-card-figure img {
  width: 100%;
  height: 100%;
  object-fit: contain;
  display: block;
}

.formula-card-title,
.question-card-title {
  margin: 0;
  font-size: 1.08rem;
}

.formula-card-body {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.topic-card-body {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.topic-card-header {
  display: flex;
  align-items: start;
  justify-content: space-between;
  gap: 10px;
}

.formula-card-meta,
.question-card-meta {
  margin: 6px 0 0;
  color: var(--muted);
  font-size: 0.85rem;
  line-height: 1.5;
}

.formula-card-footer {
  margin-top: 10px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 8px;
  flex-wrap: wrap;
}

.formula-card-footer .pill {
  flex-shrink: 0;
}

.formula-id-pill {
  max-width: 150px;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.topic-split-count {
  color: var(--muted);
  font-size: 0.8rem;
}

.formula-hero {
  display: block;
}

.formula-stage {
  min-height: 320px;
  margin-bottom: 20px;
}

.formula-stage-empty {
  min-height: 280px;
}

#formula-detail-empty {
  overflow: hidden;
  display: grid;
  place-items: center;
  text-align: center;
  align-content: center;
}

#formula-stage-placeholder {
  display: grid;
  gap: 10px;
  justify-items: center;
}

#formula-stage-image {
  width: auto;
  max-width: 100%;
  max-height: 320px;
  object-fit: contain;
  display: block;
  margin: 0 auto;
  align-self: center;
  justify-self: center;
}

.question-stage {
  margin-bottom: 24px;
}

.question-stage-toolbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 12px;
  flex-wrap: wrap;
}

.question-stage-pagination {
  display: inline-flex;
  align-items: center;
  gap: 10px;
}

.stage-nav-btn {
  border: 1px solid var(--line);
  background: #fff;
  color: var(--ink);
  border-radius: 999px;
  padding: 8px 14px;
  font: inherit;
  font-weight: 700;
  cursor: pointer;
}

.stage-nav-btn:disabled {
  opacity: 0.45;
  cursor: default;
}

.question-stage-hint {
  margin: 0;
}

.question-stage-images {
  position: relative;
  min-height: 520px;
  border: 1px solid rgba(116, 100, 82, 0.14);
  border-radius: 20px;
  background:
    linear-gradient(180deg, rgba(180, 79, 42, 0.04), rgba(31, 106, 87, 0.04)),
    #fff;
  overflow: hidden;
}

.question-stage-section-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin: 0;
  padding: 12px 16px 10px;
  border-top: 1px solid rgba(116, 100, 82, 0.14);
  background: rgba(255, 255, 255, 0.9);
}

.question-stage-section-head h3 {
  margin: 0;
  font-size: 1rem;
}

.mark-scheme-image-list {
  display: grid;
  gap: 12px;
  padding: 0 16px 16px;
  background: #fff;
}

.mark-scheme-image-card {
  margin: 0;
  border: 1px solid rgba(116, 100, 82, 0.14);
  border-radius: 12px;
  background: #fff;
  overflow: hidden;
}

.mark-scheme-image-card figcaption {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 10px 12px;
  border-bottom: 1px solid rgba(116, 100, 82, 0.12);
  color: var(--muted);
  font-size: 0.82rem;
  font-weight: 800;
}

.mark-scheme-image-actions {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  white-space: nowrap;
}

.mark-scheme-open-link {
  display: inline-flex;
  align-items: center;
  min-height: 28px;
  padding: 0 10px;
  border: 1px solid rgba(31, 106, 87, 0.22);
  border-radius: 8px;
  color: var(--accent);
  background: rgba(31, 106, 87, 0.06);
  text-decoration: none;
}

.mark-scheme-open-link:hover {
  background: rgba(31, 106, 87, 0.12);
}

.mark-scheme-image-scroll {
  max-height: min(72vh, 760px);
  overflow: auto;
  background: #fff;
}

.mark-scheme-image-card img {
  width: 100%;
  height: auto;
  display: block;
  background: #fff;
}

.question-stage-viewport {
  position: relative;
  min-height: 520px;
  overflow: hidden;
  cursor: grab;
  touch-action: none;
}

.question-stage-viewport.dragging {
  cursor: grabbing;
}

#question-stage-active-image {
  position: absolute;
  top: 50%;
  left: 50%;
  max-width: min(100%, 1200px);
  max-height: min(100%, 960px);
  object-fit: contain;
  display: block;
  transform-origin: center center;
  user-select: none;
  -webkit-user-drag: none;
}

#question-stage-empty {
  min-height: 100%;
  border: 0;
  background: transparent;
}

.formula-copy h2 {
  font-size: clamp(1.35rem, 2vw, 2rem);
  margin-top: 2px;
}

.stat-row {
  margin-top: 18px;
  justify-content: flex-start;
  flex-wrap: wrap;
}

.stat-card {
  min-width: 0;
  padding: 12px 14px;
  border-radius: 16px;
  border: 1px solid rgba(116, 100, 82, 0.12);
  background: var(--paper-strong);
}

.stat-card strong {
  display: block;
  margin-top: 4px;
  font-size: 1.25rem;
}

.question-sections {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
  gap: 16px;
  margin-top: 18px;
}

body[data-browse-mode="question"] #formula-detail-empty,
body[data-browse-mode="question"] #formula-detail,
body[data-browse-mode="question"] .question-sections {
  display: none !important;
}

.side-section:first-child {
  margin-top: 0;
}

.side-meta h3 {
  margin-top: 0;
  margin-bottom: 6px;
  font-size: 1.35rem;
}

.side-stats {
  margin-top: 12px;
  display: grid;
  grid-template-columns: 1fr;
}

.side-stats .stat-card {
  min-width: 0;
}

.question-group {
  min-width: 0;
}

.group-head h3 {
  font-size: 1.2rem;
}

.question-card-summary {
  margin: 10px 0 0;
  color: var(--ink);
  line-height: 1.6;
  font-size: 0.96rem;
}

.meta-grid {
  display: grid;
  grid-template-columns: 88px 1fr;
  gap: 10px 14px;
  margin: 10px 0 0;
}

.meta-grid dt {
  color: var(--muted);
}

.meta-grid dd {
  margin: 0;
  font-weight: 600;
}

.question-image-frame {
  border: 1px solid rgba(116, 100, 82, 0.14);
  border-radius: 16px;
  padding: 8px;
  background: #fff;
}

.question-image-frame img {
  width: 100%;
  display: block;
  border-radius: 10px;
}

.detail-section {
  margin-top: 14px;
}

.detail-section h4 {
  margin-bottom: 8px;
  font-size: 0.96rem;
}

.detail-chip-group + .detail-chip-group {
  margin-top: 16px;
}

.mark-scheme-list {
  display: grid;
  gap: 10px;
}

.mark-scheme-card {
  border: 1px solid rgba(31, 106, 87, 0.18);
  border-radius: 8px;
  background: rgba(31, 106, 87, 0.04);
  overflow: hidden;
}

.mark-scheme-card summary {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 10px 12px;
  cursor: pointer;
  color: var(--ink);
  font-weight: 800;
}

.mark-scheme-body {
  border-top: 1px solid rgba(31, 106, 87, 0.14);
  padding: 12px;
  background: #fff;
}

.mark-scheme-meta {
  margin: 0 0 10px;
  color: var(--muted);
  font-size: 0.82rem;
  font-weight: 700;
}

.mark-scheme-body pre {
  margin: 0;
  white-space: pre-wrap;
  overflow-wrap: anywhere;
  font-family: inherit;
  line-height: 1.55;
  color: var(--ink);
}

.mark-scheme-notes {
  margin-top: 12px;
  padding-top: 12px;
  border-top: 1px solid rgba(116, 100, 82, 0.14);
}

.mark-scheme-notes h5 {
  margin: 0 0 6px;
  color: var(--muted);
  font-size: 0.8rem;
  text-transform: uppercase;
}

.chip-row {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.chip {
  display: inline-flex;
  align-items: center;
  padding: 6px 10px;
  border-radius: 999px;
  background: rgba(180, 79, 42, 0.1);
  color: var(--accent-strong);
  font-size: 0.8rem;
  font-weight: 700;
}

.empty-state {
  min-height: 220px;
  display: grid;
  place-items: center;
  text-align: center;
  color: var(--muted);
  border: 1px dashed rgba(116, 100, 82, 0.22);
  border-radius: 18px;
  background: linear-gradient(180deg, rgba(180, 79, 42, 0.02), rgba(31, 106, 87, 0.03));
  padding: 20px;
}

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

.empty-state.compact {
  min-height: 80px;
}

.empty-list {
  padding: 18px 14px;
  border: 1px dashed rgba(116, 100, 82, 0.22);
  border-radius: 16px;
  color: var(--muted);
  background: rgba(255, 255, 255, 0.68);
}

.tiny {
  font-size: 0.8rem;
  line-height: 1.6;
}

.site-footer {
  padding: 18px 0 4px;
  text-align: center;
  color: var(--muted);
  font-size: 0.78rem;
}

.site-footer a {
  color: inherit;
  text-decoration: none;
}

.site-footer a:hover {
  color: var(--accent-strong);
  text-decoration: underline;
}

@media (max-width: 1180px) {
  .layout,
  .content,
  .hero,
  .formula-hero,
  .question-sections {
    grid-template-columns: 1fr;
  }

  .formula-detail-panel,
  .question-detail-panel {
    grid-column: auto;
    position: static;
    max-height: none;
    overflow: visible;
  }

}

@media (max-width: 720px) {
  .page-shell {
    width: min(100%, calc(100% - 20px));
    padding-top: 12px;
  }

  .hero-copy,
  .hero-panel,
  .panel {
    padding: 16px;
  }

  .formula-card {
    gap: 10px;
  }

  .question-stage-images {
    min-height: 360px;
  }
}