*, *::before, *::after {
  box-sizing: border-box;
}

body {
  margin: 0;
  padding: 16px;
  font-family: var(--font-sans, system-ui, -apple-system, sans-serif);
  color: var(--color-text-primary);
  background: var(--color-background-primary);
  line-height: 1.45;
}

.page {
  display: flex;
  flex-direction: column;
  gap: 14px;
  max-width: 1180px;
  margin: 0 auto;
}

.page-header {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.header-top {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
}

.back-link {
  color: var(--color-text-info);
  text-decoration: none;
  font-size: 13px;
  font-weight: 600;
}

.back-link:hover {
  text-decoration: underline;
}

.level-tag {
  font-size: 12px;
  font-weight: 600;
  padding: 2px 8px;
  border-radius: var(--border-radius-sm, 4px);
  background: var(--color-background-secondary);
  color: var(--color-text-secondary);
  border: 1px solid var(--color-border-primary);
}

h1 {
  font-size: 20px;
  margin: 0;
  font-weight: 700;
}

.subtitle {
  margin: 0;
  font-size: 13.5px;
  color: var(--color-text-secondary);
}

.preset-bar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 6px;
}

.bar-label {
  font-size: 12.5px;
  font-weight: 600;
  color: var(--color-text-secondary);
  margin-right: 2px;
}

.btn-chip, .btn-mini {
  font-family: inherit;
  font-size: 12.5px;
  font-weight: 500;
  padding: 5px 10px;
  border-radius: var(--border-radius-sm, 6px);
  border: 1px solid var(--color-border-primary);
  background: var(--color-background-secondary);
  color: var(--color-text-primary);
  cursor: pointer;
}

.btn-mini {
  font-size: 12px;
  padding: 4px 8px;
}

.btn-chip:hover, .btn-mini:hover {
  border-color: var(--color-border-secondary);
}

.btn-chip.active, .btn-mini.active {
  background: var(--color-background-info);
  color: var(--color-text-info);
  border-color: var(--color-text-info);
  font-weight: 600;
}

.workspace {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 440px), 1fr));
  gap: 14px;
  align-items: start;
}

.visual-col, .maths-col {
  display: flex;
  flex-direction: column;
  gap: 12px;
  min-width: 0;
}

.canvas-card, .calc-card {
  border: 1px solid var(--color-border-primary);
  border-radius: var(--border-radius-md, 8px);
  background: var(--color-background-secondary);
  padding: 12px;
  display: flex;
  flex-direction: column;
  gap: 10px;
  min-width: 0;
}

.canvas-toolbar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
}

.drag-mode-group, .view-btn-group {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 4px;
}

.toolbar-caption {
  font-size: 12px;
  font-weight: 600;
  color: var(--color-text-secondary);
  margin-right: 2px;
}

.canvas-wrap {
  position: relative;
  width: 100%;
  border: 1px solid var(--color-border-primary);
  border-radius: var(--border-radius-sm, 6px);
  background: var(--color-background-primary);
  overflow: hidden;
}

#vec-canvas {
  display: block;
  width: 100%;
  height: auto;
  aspect-ratio: 16 / 11;
  touch-action: none;
  cursor: grab;
}

#vec-canvas:active {
  cursor: grabbing;
}

.canvas-legend {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  padding: 6px 10px;
  border-top: 1px solid var(--color-border-primary);
  background: var(--color-background-secondary);
  font-size: 12px;
}

.leg-item {
  display: inline-flex;
  align-items: center;
  gap: 5px;
}

.swatch {
  display: inline-block;
  width: 10px;
  height: 10px;
  border-radius: 50%;
}

.sw-a { background: var(--traycer-chart-1, #2563eb); }
.sw-b { background: var(--traycer-chart-2, #d97706); }
.sw-cross { background: var(--traycer-chart-3, #16a34a); }
.sw-plane { background: var(--traycer-chart-4, #9333ea); }

.layer-toggles {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  font-size: 12.5px;
}

.chk-label, .radio-label {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  cursor: pointer;
  color: var(--color-text-primary);
}

.controls-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 210px), 1fr));
  gap: 10px;
}

.vec-box {
  margin: 0;
  padding: 10px;
  border: 1px solid var(--color-border-primary);
  border-radius: var(--border-radius-md, 8px);
  background: var(--color-background-secondary);
  display: flex;
  flex-direction: column;
  gap: 6px;
  min-width: 0;
}

.vec-box legend {
  font-size: 12.5px;
  font-weight: 600;
  padding: 0 4px;
  display: inline-flex;
  align-items: center;
  gap: 5px;
}

.slider-row {
  display: grid;
  grid-template-columns: 24px 1fr 34px;
  align-items: center;
  gap: 6px;
  font-size: 12.5px;
}

.slider-row label {
  font-weight: 600;
  font-family: var(--font-mono, monospace);
}

.slider-row input[type="range"] {
  width: 100%;
  margin: 0;
}

.slider-row output {
  font-family: var(--font-mono, monospace);
  font-size: 12px;
  text-align: right;
  font-weight: 600;
}

.normal-mode-row {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  font-size: 12.5px;
}

.custom-n-wrap {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.custom-n-wrap[hidden] {
  display: none;
}

.helper-note {
  margin: 0;
  font-size: 12px;
  color: var(--color-text-secondary);
}

.card-head {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 6px;
}

.card-head h2 {
  font-size: 15px;
  margin: 0;
  font-weight: 700;
}

.status-pill {
  font-size: 11.5px;
  font-weight: 600;
  padding: 2px 8px;
  border-radius: var(--border-radius-sm, 4px);
  background: var(--color-background-info);
  color: var(--color-text-info);
}

.concept-note {
  margin: 0;
  font-size: 12.5px;
  color: var(--color-text-secondary);
}

.formula-block {
  background: var(--color-background-primary);
  border: 1px solid var(--color-border-primary);
  border-radius: var(--border-radius-sm, 6px);
  padding: 10px;
  font-family: var(--font-mono, monospace);
  font-size: 12.5px;
  display: flex;
  flex-direction: column;
  gap: 6px;
  overflow-x: auto;
}

.math-line {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 6px;
}

.math-label {
  font-family: var(--font-sans, sans-serif);
  font-size: 12px;
  font-weight: 600;
  color: var(--color-text-secondary);
  min-width: 110px;
}

.math-expr {
  color: var(--color-text-primary);
}

.math-highlight {
  font-weight: 700;
  color: var(--color-text-info);
}

.math-divider {
  border: 0;
  border-top: 1px dashed var(--color-border-primary);
  margin: 2px 0;
}