:root {
  --bg: #f4f7f8;
  --panel: #ffffff;
  --ink: #17202a;
  --muted: #60717d;
  --line: #d4dde2;
  --positive: #c9362c;
  --negative: #2368b8;
  --primary: #16625b;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: "Segoe UI", Roboto, Arial, sans-serif;
  color: var(--ink);
  background:
    linear-gradient(90deg, rgba(23, 32, 42, 0.04) 1px, transparent 1px),
    linear-gradient(rgba(23, 32, 42, 0.04) 1px, transparent 1px),
    var(--bg);
  background-size: 28px 28px;
}

button,
input {
  font: inherit;
}

.app {
  width: min(1440px, 100%);
  margin: 0 auto;
  padding: 16px;
}

.workspace {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 320px;
  align-items: start;
  gap: 16px;
  min-height: calc(100vh - 32px);
}

.stage,
.panel {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 8px;
  box-shadow: 0 18px 44px rgba(23, 32, 42, 0.1);
}

.stage {
  overflow: hidden;
  display: grid;
  grid-template-rows: auto minmax(480px, calc(100vh - 226px)) auto auto;
}

.topbar {
  display: flex;
  justify-content: space-between;
  align-items: start;
  gap: 16px;
  padding: 14px 16px;
  border-bottom: 1px solid var(--line);
}

.topbar h1 {
  margin: 2px 0 0;
  font-size: 30px;
}

.eyebrow {
  margin: 0 0 8px;
  color: var(--muted);
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.readout {
  min-width: 260px;
  padding: 10px 12px;
  border: 1px solid var(--line);
  border-radius: 8px;
  color: var(--muted);
  background: #f8fbfc;
  font-size: 14px;
  line-height: 1.4;
}

#fieldCanvas {
  display: block;
  width: 100%;
  height: 100%;
  background: #fbfdfe;
  cursor: crosshair;
}

.canvas-legend {
  display: flex;
  flex-wrap: wrap;
  gap: 14px;
  align-items: center;
  padding: 8px 12px;
  border-top: 1px solid var(--line);
  background: #ffffff;
  color: var(--muted);
  font-size: 13px;
  font-weight: 700;
}

.canvas-legend span {
  display: inline-flex;
  align-items: center;
  gap: 8px;
}

.legend-line {
  display: inline-block;
  width: 36px;
  height: 0;
  border-top: 3px solid;
}

.legend-line--field {
  border-color: #125c54;
}

.stage--draw #fieldCanvas {
  cursor: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='24' height='24' viewBox='0 0 24 24'%3E%3Cpath fill='%2317202a' d='M5 19.1 6.1 15l9.8-9.8 3 3-9.8 9.8L5 19.1Zm12-12 1-1a1.4 1.4 0 0 0 0-2l-.1-.1a1.4 1.4 0 0 0-2 0l-1 1 2.1 2.1Z'/%3E%3C/svg%3E") 2 22, crosshair;
}

.mode-bar {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 8px;
  padding: 10px;
  border-top: 1px solid var(--line);
  background: #f8fbfc;
}

.mode-btn {
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 11px 12px;
  color: var(--ink);
  background: #fff;
  cursor: pointer;
  font-weight: 800;
}

.mode-btn:disabled,
.mode-btn[aria-disabled="true"] {
  opacity: 0.45;
}

.mode-btn--active {
  color: #fff;
  border-color: var(--primary);
  background: var(--primary);
}

.panel {
  max-height: calc(100vh - 32px);
  overflow: auto;
  padding: 16px;
  display: grid;
  align-content: start;
  gap: 22px;
}

.button-grid {
  display: grid;
  gap: 8px;
}

.btn {
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 10px 12px;
  color: var(--ink);
  background: #fff;
  cursor: pointer;
  font-weight: 700;
}

.btn:hover {
  border-color: #9fb3bd;
}

.btn.primary {
  color: #fff;
  border-color: var(--positive);
  background: var(--positive);
}

.btn.negative {
  color: #fff;
  border-color: var(--negative);
  background: var(--negative);
}

.btn.primary-action {
  color: #fff;
  border-color: var(--primary);
  background: var(--primary);
}

.lab-card {
  padding: 14px;
  border: 1px solid #b7c9d0;
  border-radius: 8px;
  background: #f8fbfc;
}

.lab-card h2 {
  margin: 0 0 8px;
  font-size: 22px;
}

.lab-task {
  margin: 12px 0;
  padding: 10px 12px;
  border-left: 4px solid var(--primary);
  background: #ffffff;
  color: var(--ink);
  line-height: 1.45;
}

.test-charge-callout {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 10px;
  align-items: center;
  margin: 12px 0;
  padding: 10px;
  border: 1px solid #dfc46a;
  border-radius: 8px;
  background: #fff9df;
}

.test-charge-callout p {
  margin: 0;
  color: var(--ink);
  line-height: 1.35;
}

.test-charge-icon {
  display: grid;
  place-items: center;
  width: 36px;
  height: 36px;
  border: 4px solid #ffd166;
  border-radius: 50%;
  color: #fff;
  background: #1f2d36;
  font-weight: 900;
}

#labResponse {
  width: 100%;
  min-height: 92px;
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 10px 12px;
  color: var(--ink);
  background: #fff;
  resize: vertical;
}

.assessment-answer {
  display: grid;
  gap: 8px;
  margin: 12px 0;
}

.assessment-choice {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 8px;
  align-items: start;
  padding: 9px 10px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
}

.assessment-short {
  width: 100%;
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 10px 12px;
  color: var(--ink);
  background: #fff;
}

.modal-backdrop {
  position: fixed;
  inset: 0;
  z-index: 20;
  display: grid;
  place-items: center;
  padding: 20px;
  background: rgba(23, 32, 42, 0.52);
}

.modal-backdrop[hidden] {
  display: none;
}

.modal {
  width: min(420px, 100%);
  padding: 18px;
  border-radius: 8px;
  background: #fff;
  box-shadow: 0 24px 70px rgba(0, 0, 0, 0.28);
}

.modal h2 {
  margin: 0 0 8px;
}

.modal p {
  margin: 0 0 16px;
  color: var(--muted);
  line-height: 1.45;
}

.control,
.toggle {
  display: grid;
  gap: 8px;
  color: var(--ink);
  font-weight: 700;
}

.toggle {
  grid-template-columns: auto 1fr;
  align-items: center;
  margin: 10px 0;
  font-weight: 600;
}

input[type="range"] {
  width: 100%;
}

.hint,
.notes {
  color: var(--muted);
  font-size: 14px;
  line-height: 1.45;
}

.hint {
  margin: 8px 0 0;
}

.notes {
  margin: 0;
  padding-left: 18px;
}

.notes li + li {
  margin-top: 6px;
}

@media (max-width: 920px) {
  .workspace {
    grid-template-columns: 1fr;
  }

  .topbar {
    display: grid;
  }

  .readout {
    min-width: 0;
  }

  #fieldCanvas {
    min-height: 0;
  }
}