:root {
  --bg: #f3f7f6;
  --surface: #ffffff;
  --surface-2: #eef5f4;
  --ink: #17211f;
  --muted: #586763;
  --line: #c9d7d3;
  --water: #1686a0;
  --water-dark: #0f6074;
  --field: #5e8d45;
  --gold: #c18a20;
  --warning: #c6422b;
  --sediment: #77716a;
  --ok: #24714e;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: "Segoe UI", Roboto, Arial, sans-serif;
  color: var(--ink);
  background:
    linear-gradient(180deg, rgba(22, 134, 160, 0.08), rgba(94, 141, 69, 0.07)),
    var(--bg);
}

button,
input,
select,
textarea {
  font: inherit;
}

.app {
  width: min(1460px, 100%);
  margin: 0 auto;
  padding: 18px;
  display: flex;
  flex-direction: column;
}

.topbar {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(280px, 480px);
  gap: 18px;
  align-items: end;
  margin-bottom: 14px;
}

.eyebrow {
  margin: 0 0 6px;
  color: #31584c;
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0;
  text-transform: uppercase;
}

h1,
h2,
h3 {
  margin: 0;
  line-height: 1.1;
}

h1 {
  font-size: 2.1rem;
}

h2 {
  font-size: 1.24rem;
}

h3 {
  font-size: 1rem;
}

.summary,
.hint,
.feedback,
.concept-card p,
.misconceptions p,
.lesson-intro p,
.data-card span,
.impact-grid span,
.impact-grid small,
.task-box,
.concept-question {
  color: var(--muted);
}

.summary {
  margin: 0;
  line-height: 1.45;
}

.page-nav,
.page-panel,
.concept-card,
.misconceptions,
.scene-frame,
.data-card,
.panel-block,
.checkpoint,
.question-block,
.sample-response {
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--surface);
}

.page-nav {
  display: flex;
  gap: 8px;
  padding: 8px;
  margin-bottom: 14px;
}

.tab-btn,
.btn {
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 10px 14px;
  background: #fff;
  color: var(--ink);
  font-weight: 700;
  cursor: pointer;
}

.tab-btn.active,
.btn.primary {
  border-color: #17626a;
  background: #17626a;
  color: #fff;
}

.tab-btn:disabled,
.tab-btn[aria-disabled="true"] {
  cursor: not-allowed;
  opacity: 0.62;
}

.unlock-status {
  margin: -4px 0 12px;
  color: #526561;
  font-weight: 700;
}

.page-panel {
  padding: 14px;
  animation: panel-in 180ms ease-out;
}

.tab-panel[hidden] {
  display: none;
}

.lesson-intro {
  padding: 8px 4px 16px;
  max-width: 920px;
}

.lesson-intro h2 {
  font-size: 1.55rem;
}

.lesson-intro p {
  margin: 10px 0 0;
  line-height: 1.5;
}

.concept-strip {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 10px;
  margin-bottom: 14px;
}

.concept-card {
  padding: 13px;
}

.concept-card p {
  margin: 8px 0 0;
  line-height: 1.38;
}

.misconceptions {
  padding: 14px;
}

.misconception-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 12px;
  margin-top: 12px;
}

.misconception-grid article {
  padding-top: 10px;
  border-top: 4px solid var(--gold);
}

.misconception-grid p {
  margin: 8px 0 0;
}

.lab-shell {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(320px, 390px);
  gap: 14px;
  align-items: start;
}

.scene-zone,
.control-panel,
.data-card,
.page-panel,
.checkpoint,
.question-block {
  min-width: 0;
}

.scene-frame {
  background: #dfece8;
  overflow: hidden;
}

#popCanvas {
  display: block;
  width: 100%;
  height: min(58vh, 620px);
  min-height: 420px;
  background: #dcece7;
}

.data-zone {
  display: grid;
  grid-template-columns: minmax(320px, 0.9fr) minmax(360px, 1.1fr);
  gap: 10px;
  margin-top: 10px;
}

.data-card,
.panel-block {
  padding: 14px;
}

#graphCanvas {
  display: block;
  width: 100%;
  height: 230px;
}

.concentration-table {
  display: grid;
  gap: 9px;
}

.organism-row {
  display: grid;
  grid-template-columns: minmax(120px, 1fr) minmax(96px, auto);
  gap: 10px;
  align-items: center;
}

.meter-track {
  grid-column: 1 / -1;
  height: 10px;
  border-radius: 999px;
  background: #e5ece9;
  overflow: hidden;
}

.meter-fill {
  height: 100%;
  width: 0%;
  border-radius: 999px;
  background: linear-gradient(90deg, var(--water), var(--gold), var(--warning));
  transition: width 260ms ease;
  background-size: 180% 100%;
  animation: meter-flow 1.8s linear infinite;
}

.organism-name {
  font-weight: 700;
}

.organism-value {
  font-variant-numeric: tabular-nums;
  font-weight: 800;
  text-align: right;
  white-space: nowrap;
}

.control-panel {
  display: grid;
  gap: 10px;
}

.panel-block h2 {
  margin-bottom: 8px;
}

.panel-block p {
  line-height: 1.42;
}

.task-box {
  border-left: 4px solid var(--water);
  padding: 10px 12px;
  margin: 10px 0;
  background: var(--surface-2);
}

.step-actions,
.checkpoint-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  align-items: center;
}

.control {
  display: grid;
  gap: 7px;
  margin-top: 12px;
}

.control span {
  font-size: 0.82rem;
  font-weight: 800;
  text-transform: uppercase;
}

.control output {
  color: var(--muted);
  font-weight: 700;
}

input[type="range"] {
  width: 100%;
  accent-color: #17626a;
}

select,
textarea {
  width: 100%;
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 10px 11px;
  background: #fff;
  color: var(--ink);
}

.result-panel {
  background: #fbfcfc;
}

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

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

.impact-grid span,
.impact-grid small {
  display: block;
}

.impact-grid strong {
  display: block;
  margin: 5px 0;
  overflow-wrap: anywhere;
}

@keyframes meter-flow {
  from {
    background-position: 0% 50%;
  }

  to {
    background-position: 180% 50%;
  }
}

@keyframes panel-in {
  from {
    opacity: 0.72;
    transform: translateY(3px);
  }

  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.checkpoint {
  padding: 16px;
}

.assessment-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
  margin-top: 14px;
}

.question-block {
  padding: 14px;
  margin: 0;
}

.question-block legend {
  font-weight: 800;
  line-height: 1.35;
}

.question-block label {
  display: block;
  margin-top: 10px;
  line-height: 1.36;
}

.question-block input {
  margin-right: 7px;
}

.cer-block,
.checkpoint-actions {
  grid-column: 1 / -1;
}

.cer-response {
  min-height: 120px;
  resize: vertical;
}

.feedback {
  margin: 0;
  font-weight: 800;
}

.feedback .ok {
  color: var(--ok);
}

.feedback .bad {
  color: var(--warning);
}

.sample-response {
  width: 100%;
  padding: 12px;
  margin-top: 6px;
  background: var(--surface-2);
}

.sample-response p:last-child {
  margin: 0;
  line-height: 1.45;
}

@media (max-width: 1080px) {
  .topbar,
  .lab-shell,
  .data-zone {
    grid-template-columns: 1fr;
  }

  #popCanvas {
    height: 520px;
  }
}

@media (max-width: 780px) {
  .app {
    padding: 12px;
  }

  h1 {
    font-size: 1.75rem;
  }

  .concept-strip,
  .misconception-grid,
  .assessment-grid,
  .impact-grid {
    grid-template-columns: 1fr;
  }

  .page-nav {
    flex-wrap: wrap;
  }

  .tab-btn,
  .btn {
    flex: 1 1 auto;
  }

  #popCanvas {
    min-height: 360px;
    height: 62vh;
  }
}