:root {
  --bg: #f4f6f8;
  --panel: #ffffff;
  --ink: #1d2433;
  --muted: #687386;
  --line: #dfe4ea;
  --accent: #0f9f7a;
  --accent-dark: #08765b;
  --warn: #c24b3a;
  --gold: #a46a00;
  --draw: #e44747;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  display: grid;
  grid-template-columns: 320px minmax(0, 1fr);
  background: var(--bg);
  color: var(--ink);
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

button,
select,
input {
  font: inherit;
}

button {
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  color: var(--ink);
  min-height: 40px;
  padding: 0 14px;
  cursor: pointer;
}

button:hover {
  border-color: #aeb8c5;
}

button.active {
  border-color: var(--accent);
  color: var(--accent-dark);
  background: #ecfbf6;
}

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

.sidebar {
  height: 100vh;
  overflow: auto;
  padding: 20px;
  border-right: 1px solid var(--line);
  background: var(--panel);
}

.brand {
  display: flex;
  gap: 12px;
  align-items: center;
  margin-bottom: 22px;
}

.brand-mark {
  width: 44px;
  height: 44px;
  border-radius: 8px;
  display: grid;
  place-items: center;
  background: #16324f;
  color: #fff;
  font-weight: 800;
}

h1,
h2,
p {
  margin: 0;
}

h1 {
  font-size: 22px;
}

.brand p,
.crumb,
.field span,
.stats span,
.answer-summary {
  color: var(--muted);
  font-size: 13px;
}

.subject-tabs {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
  margin-bottom: 16px;
}

.field {
  display: grid;
  gap: 8px;
  margin-bottom: 14px;
}

select,
input {
  width: 100%;
  min-height: 42px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  padding: 0 10px;
  color: var(--ink);
}

.stats {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 8px;
  margin: 14px 0;
}

.stats div {
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 10px;
  background: #fafbfc;
}

.stats strong,
.stats span {
  display: block;
}

.stats strong {
  font-size: 22px;
}

.jump {
  display: grid;
  grid-template-columns: 1fr 78px;
  gap: 8px;
  margin-bottom: 14px;
}

.nav-toggle {
  display: none;
  width: 100%;
  margin-bottom: 10px;
}

.page-grid {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 6px;
}

.page-grid button {
  min-height: 34px;
  padding: 0;
  border-radius: 6px;
  font-size: 13px;
}

.page-grid button.done {
  background: #edf8f3;
  border-color: #92d4bd;
}

.page-grid button.wrong {
  background: #fff1ef;
  border-color: #ebb0a8;
}

.page-grid button.favorite {
  color: var(--gold);
  border-color: #ddb56e;
}

.main {
  min-width: 0;
  height: 100vh;
  display: grid;
  grid-template-rows: auto minmax(0, 1fr) auto auto;
}

.toolbar,
.actions,
.answer-panel {
  background: rgba(255, 255, 255, 0.94);
  border-bottom: 1px solid var(--line);
  padding: 14px 22px;
  display: flex;
  justify-content: space-between;
  gap: 16px;
  align-items: center;
}

.toolbar-actions,
.mark-actions,
.choice-buttons,
.answer-tools {
  display: flex;
  gap: 8px;
  align-items: center;
}

h2 {
  margin-top: 4px;
  font-size: 22px;
}

.viewer {
  overflow: auto;
  padding: 22px;
  display: flex;
  justify-content: center;
  align-items: flex-start;
}

.viewer-frame {
  position: relative;
  width: min(100%, 1120px);
  background: #fff;
  box-shadow: 0 14px 40px rgba(21, 31, 45, 0.13);
}

.viewer-frame.natural {
  width: auto;
  max-width: none;
}

.viewer img {
  width: 100%;
  height: auto;
  display: block;
  background: #fff;
}

.viewer-frame.natural img {
  width: auto;
  max-width: none;
}

#drawingCanvas {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
  touch-action: none;
}

.draw-mode #drawingCanvas {
  pointer-events: auto;
  cursor: crosshair;
}

.choice-buttons button {
  min-width: 52px;
  padding: 0 16px;
  font-weight: 700;
}

.choice-buttons button.selected {
  border-color: var(--accent);
  background: var(--accent);
  color: #fff;
}

.answer-summary {
  min-width: 130px;
  text-align: right;
}

#clearPaperAnswersBtn {
  white-space: nowrap;
}

.answer-summary.correct {
  color: var(--accent-dark);
  font-weight: 700;
}

.answer-summary.wrong {
  color: var(--warn);
  font-weight: 700;
}

.answer-summary.unknown {
  color: var(--gold);
  font-weight: 700;
}

.actions {
  border-top: 1px solid var(--line);
  border-bottom: 0;
}

#wrongBtn.active {
  border-color: var(--warn);
  background: #fff1ef;
  color: var(--warn);
}

#favBtn.active {
  border-color: #d39a39;
  background: #fff7e7;
  color: var(--gold);
}

#drawBtn.active {
  border-color: var(--draw);
  background: #fff1f1;
  color: var(--draw);
}

@media (max-width: 860px) {
  body {
    display: grid;
    grid-template-columns: 1fr;
    grid-template-rows: auto minmax(0, 1fr);
    min-height: 100vh;
  }

  .sidebar {
    height: auto;
    max-height: none;
    border-right: 0;
    border-bottom: 1px solid var(--line);
    padding: 10px;
    overflow: visible;
  }

  .brand {
    margin-bottom: 10px;
  }

  .brand-mark {
    width: 34px;
    height: 34px;
    font-size: 15px;
  }

  h1 {
    font-size: 18px;
  }

  .brand p {
    display: none;
  }

  .subject-tabs,
  .field,
  .jump,
  .stats {
    margin-bottom: 8px;
  }

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

  .stats div {
    padding: 6px 8px;
  }

  .stats strong {
    font-size: 18px;
  }

  .nav-toggle {
    display: block;
  }

  .page-grid {
    display: none;
    max-height: 34vh;
    overflow: auto;
    padding-bottom: 4px;
  }

  .sidebar.nav-open .page-grid {
    display: grid;
  }

  .main {
    height: auto;
    min-height: 0;
    grid-template-rows: auto minmax(0, 1fr) auto auto;
  }

  .toolbar,
  .actions,
  .answer-panel {
    padding: 10px;
    flex-wrap: wrap;
  }

  .toolbar-actions {
    display: grid;
    grid-template-columns: repeat(4, minmax(0, 1fr));
    width: 100%;
  }

  .toolbar-actions button {
    padding: 0 8px;
  }

  .answer-panel {
    align-items: stretch;
  }

  .choice-buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    width: 100%;
  }

  .answer-summary {
    width: 100%;
    text-align: left;
  }

  .answer-tools {
    display: grid;
    grid-template-columns: auto minmax(0, 1fr);
    width: 100%;
  }

  .mark-actions {
    order: 3;
    width: 100%;
    display: grid;
    grid-template-columns: repeat(3, 1fr);
  }

  .viewer {
    padding: 10px;
    align-items: stretch;
  }

  .viewer-frame {
    width: 100%;
    box-shadow: none;
  }
}