:root {
  --chart-blue: #0b4761;
  --chart-paper: #f7f4e9;
  --chart-line: #f15d40;
}

.study-tools {
  grid-template-columns: repeat(4, 1fr);
}

.chart-tool-card {
  background: linear-gradient(145deg, #fff 0%, #eef8f5 100%);
  border-color: #d2e8e3;
}

.chart-page {
  max-width: 1680px;
  min-height: 80vh;
  margin: 0 auto;
  padding: 38px clamp(14px, 3vw, 46px) 80px;
}

.chart-page-head {
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  gap: 24px;
  margin-bottom: 24px;
}

.chart-page-head h2 {
  margin: 7px 0 5px;
  color: var(--navy);
  font: 800 clamp(30px, 4vw, 48px)/1.08 Manrope;
}

.chart-page-head p {
  max-width: 760px;
  margin: 0;
  color: var(--muted);
}

.chart-head-actions {
  display: flex;
  flex: 0 0 auto;
  gap: 8px;
}

.chart-simulator {
  display: grid;
  grid-template-columns: 315px minmax(0, 1fr);
  gap: 18px;
  align-items: start;
}

.chart-side-panel {
  display: grid;
  gap: 14px;
}

.exercise-card,
.formula-card {
  border: 1px solid var(--line);
  border-radius: 14px;
  background: #fff;
  box-shadow: 0 12px 35px rgba(9, 45, 53, .08);
}

.exercise-card {
  padding: 22px;
}

.exercise-card > label {
  display: grid;
  gap: 7px;
  margin-top: 14px;
  color: var(--navy);
  font-size: 11px;
  font-weight: 800;
}

.exercise-card select {
  width: 100%;
  margin: 7px 0 17px;
  padding: 11px 35px 11px 12px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: white;
  color: var(--ink);
  font: 600 12px 'DM Sans';
}

#chartExerciseText h3 {
  margin: 0 0 8px;
  color: var(--navy);
  font: 750 17px/1.3 Manrope;
}

#chartExerciseText p,
#chartExerciseText li {
  color: var(--muted);
  font-size: 12px;
  line-height: 1.55;
}

#chartExerciseText ul {
  margin: 10px 0 16px;
  padding-left: 18px;
}

#chartExerciseText strong {
  color: var(--navy);
}

.exercise-progress {
  margin: 16px 0 13px;
}

.exercise-progress > span {
  color: var(--muted);
  font-size: 10px;
  font-weight: 700;
}

.exercise-progress > div {
  height: 5px;
  margin-top: 6px;
  overflow: hidden;
  border-radius: 99px;
  background: #e9eeeb;
}

.exercise-progress i {
  display: block;
  width: 33%;
  height: 100%;
  border-radius: inherit;
  background: var(--teal);
  transition: width .25s ease;
}

.exercise-card .button {
  width: 100%;
}

.chart-feedback {
  min-height: 18px;
  margin: 12px 0 0;
  color: var(--muted);
  font-size: 11px;
  line-height: 1.45;
}

.chart-feedback.success {
  color: #127052;
  font-weight: 700;
}

.chart-feedback.error {
  color: #b34a35;
}

.formula-card {
  padding: 18px;
}

.formula-card summary {
  color: var(--navy);
  font: 750 15px Manrope;
  cursor: pointer;
}

.formula-select {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 5px;
  margin: 14px 0;
}

.formula-select button {
  padding: 7px 4px;
  border: 1px solid var(--line);
  border-radius: 7px;
  background: white;
  color: var(--muted);
  font: 700 10px 'DM Sans';
  cursor: pointer;
}

.formula-select button.active {
  border-color: var(--teal);
  background: #e7f4f2;
  color: var(--teal);
}

.calculator-panel {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 7px;
}

.calculator-panel label {
  gap: 5px;
  color: var(--muted);
  font-size: 9px;
}

.calculator-panel input {
  min-width: 0;
  width: 100%;
  padding: 8px 6px;
  font-size: 12px;
}

.calculator-panel small {
  grid-column: 1 / -1;
  color: var(--muted);
  font-size: 9px;
}

.formula-card > .button {
  width: 100%;
  margin-top: 12px;
  padding: 9px;
}

#chartCalculationResult {
  display: block;
  min-height: 18px;
  margin-top: 9px;
  color: var(--teal);
  font-size: 11px;
  font-weight: 750;
}

.chart-workspace {
  min-width: 0;
  overflow: hidden;
  border: 1px solid #cbd9d7;
  border-radius: 14px;
  background: #dde6e4;
  box-shadow: 0 18px 55px rgba(9, 45, 53, .12);
}

.chart-toolbar {
  display: flex;
  align-items: center;
  gap: 5px;
  overflow-x: auto;
  padding: 9px;
  border-bottom: 1px solid #cad8d5;
  background: #fff;
  scrollbar-width: thin;
}

.chart-toolbar button,
.chart-zoom-controls button {
  flex: 0 0 auto;
  padding: 8px 10px;
  border: 1px solid transparent;
  border-radius: 7px;
  background: transparent;
  color: var(--muted);
  font: 700 10px 'DM Sans';
  cursor: pointer;
}

.chart-toolbar button span {
  display: inline-block;
  margin-right: 4px;
  color: var(--navy);
  font-size: 14px;
}

.chart-toolbar button:hover,
.chart-toolbar button.active {
  border-color: #badbd3;
  background: #e9f6f2;
  color: var(--navy);
}

.toolbar-separator {
  flex: 0 0 1px;
  width: 1px;
  height: 25px;
  margin: 0 3px;
  background: var(--line);
}

.chart-viewport {
  position: relative;
  width: 100%;
  aspect-ratio: 1400 / 990;
  min-height: 480px;
  overflow: hidden;
  background: #e7e7e2;
  touch-action: none;
}

#chartCanvas {
  display: block;
  width: 100%;
  height: 100%;
  cursor: grab;
  user-select: none;
}

#chartCanvas[data-tool="pencil"] { cursor: crosshair; }
#chartCanvas[data-tool="eraser"] { cursor: cell; }
#chartCanvas[data-tool="compass"] { cursor: crosshair; }
#chartCanvas[data-tool="protractor"] { cursor: crosshair; }
#chartCanvas[data-tool="parallel"] { cursor: copy; }
#chartCanvas[data-tool="ruler"] { cursor: crosshair; }
#chartCanvas.dragging { cursor: grabbing; }

#chartDrawings .chart-stroke,
#chartPreview .chart-stroke {
  fill: none;
  stroke: var(--chart-line);
  stroke-width: 3;
  vector-effect: non-scaling-stroke;
}

#chartDrawings .measurement,
#chartPreview .measurement {
  stroke: #076d87;
  stroke-dasharray: 7 5;
}

#chartDrawings text,
#chartPreview text,
#chartLandmarks text {
  paint-order: stroke;
  stroke: white;
  stroke-width: 4px;
  stroke-linejoin: round;
  fill: var(--navy);
  font: 800 15px 'DM Sans';
}

.landmark-dot {
  fill: #f15d40;
  stroke: white;
  stroke-width: 4px;
  vector-effect: non-scaling-stroke;
}

.solution-point {
  fill: #11946d;
  stroke: white;
  stroke-width: 4px;
  vector-effect: non-scaling-stroke;
}

.chart-loading {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  background: rgba(247, 244, 233, .92);
  color: var(--navy);
  font-size: 13px;
  font-weight: 800;
}

.chart-readout {
  position: absolute;
  left: 12px;
  bottom: 12px;
  max-width: calc(100% - 24px);
  padding: 8px 11px;
  border: 1px solid rgba(255, 255, 255, .5);
  border-radius: 8px;
  background: rgba(4, 31, 54, .88);
  color: white;
  font-size: 10px;
  pointer-events: none;
  backdrop-filter: blur(5px);
}

.chart-zoom-controls {
  display: flex;
  align-items: center;
  justify-content: flex-end;
  gap: 4px;
  padding: 8px 10px;
  border-top: 1px solid #cad8d5;
  background: white;
}

.chart-zoom-controls span {
  min-width: 45px;
  color: var(--muted);
  font-size: 10px;
  text-align: center;
}

.chart-zoom-controls button {
  border-color: var(--line);
  background: white;
}

.chart-instructions-modal {
  width: min(760px, calc(100% - 28px));
  max-height: 88vh;
}

.instruction-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 10px;
  margin-top: 20px;
}

.instruction-grid article {
  padding: 15px;
  border: 1px solid var(--line);
  border-radius: 10px;
  background: white;
}

.instruction-grid strong {
  color: var(--navy);
  font: 750 14px Manrope;
}

.instruction-grid p {
  margin: 6px 0 0;
  color: var(--muted);
  font-size: 11px;
  line-height: 1.5;
}

.chart-disclaimer {
  margin: 18px 0 0;
  color: var(--coral);
  font-size: 11px;
  font-weight: 800;
}

@media (max-width: 1180px) {
  .study-tools { grid-template-columns: repeat(2, 1fr); }
  .chart-simulator { grid-template-columns: 275px minmax(0, 1fr); }
  .chart-viewport { min-height: 420px; }
}

@media (max-width: 900px) {
  .chart-simulator { grid-template-columns: 1fr; }
  .chart-side-panel { grid-template-columns: 1fr 1fr; }
  .chart-workspace { grid-row: 1; }
  .chart-viewport { min-height: 0; }
}

@media (max-width: 600px) {
  .study-tools { grid-template-columns: 1fr; }
  .chart-page { padding: 25px 10px 70px; }
  .chart-page-head { align-items: flex-start; flex-direction: column; }
  .chart-head-actions { width: 100%; }
  .chart-head-actions .button { flex: 1; padding: 10px; }
  .chart-side-panel { grid-template-columns: 1fr; }
  .chart-toolbar { padding: 7px; }
  .chart-toolbar button { padding: 8px 9px; }
  .chart-viewport { aspect-ratio: 4 / 3; }
  .exercise-card { padding: 18px; }
  .instruction-grid { grid-template-columns: 1fr; }
}