:root {
  --bg: #f5f7f5;
  --surface: #ffffff;
  --surface-2: #eef5f2;
  --ink: #17211f;
  --muted: #586763;
  --line: #cbd8d2;
  --water: #1d8ca6;
  --water-dark: #116273;
  --heat: #d44f35;
  --green: #26734d;
  --gold: #a06a00;
  --ok: #20724a;
}

* {
  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(38, 115, 77, 0.08), rgba(29, 140, 166, 0.06)), var(--bg);
}

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

.app {
  width: min(1440px, 100%);
  margin: 0 auto;
  padding: 18px;
  display: flex;
  flex-direction: column;
}

.topbar {
  order: 0;
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(280px, 460px);
  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 {
  margin: 0;
  line-height: 1.1;
}

h1 {
  font-size: 2.15rem;
}

h2 {
  font-size: 1.25rem;
}

.summary,
.hint,
.feedback,
.model-notes p,
.concept-card p,
.explain-panel p,
.challenge-panel p,
.misconceptions p,
.site-card span,
.site-card small,
figcaption {
  color: var(--muted);
}

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

.lab-shell {
  order: 2;
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(320px, 390px);
  gap: 14px;
  align-items: start;
  margin-top: 14px;
}

.scene-zone,
.control-panel,
.checkpoint,
.model-notes,
.trial-log,
.concept-strip,
.misconceptions,
.page-panel,
.page-nav {
  min-width: 0;
}

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

.concept-card {
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 13px;
  background: #ffffff;
}

.concept-card h2 {
  font-size: 1.05rem;
}

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

.scene-frame {
  border: 2px solid #36554c;
  border-radius: 8px;
  background: #dfeadf;
  overflow: hidden;
}

#riverCanvas {
  display: block;
  width: 100%;
  height: min(62vh, 640px);
  min-height: 420px;
  background: #dcefd8;
}

.site-readouts {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 10px;
  margin-top: 10px;
  align-items: start;
}

.site-card,
.panel-block,
.explain-panel,
.challenge-panel,
.checkpoint,
.model-notes,
.trial-log,
.misconceptions,
.page-panel,
.page-nav {
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--surface);
}

.site-card {
  padding: 14px;
}

.community-impact-block {
  grid-column: 1 / -1;
}

.community-impact-grid {
  display: grid;
  grid-template-columns: minmax(260px, 0.8fr) minmax(360px, 1.2fr);
  gap: 14px;
  align-items: start;
}

.reading-pair {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 10px;
  align-items: baseline;
  padding: 8px 0;
  border-bottom: 1px solid var(--line);
}

.reading-pair span,
.impact-grid span {
  font-size: 0.82rem;
  font-weight: 700;
  text-transform: uppercase;
}

.reading-pair strong {
  color: var(--ink);
  font-size: 1.45rem;
  overflow-wrap: anywhere;
}

.do-reading strong {
  color: #0f5e70;
  font-size: 1.65rem;
}

.reading-note {
  margin: 10px 0 0;
  color: var(--muted);
  line-height: 1.35;
}

.impact-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 10px;
}

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

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

.impact-grid strong {
  margin-top: 5px;
  color: var(--ink);
  font-size: 1.08rem;
}

.impact-grid small {
  margin-top: 4px;
  line-height: 1.25;
}

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

.panel-block {
  padding: 14px;
}

.panel-block p {
  line-height: 1.4;
}

.concept-question {
  margin: 10px 0;
  padding: 10px;
  border: 1px solid #b8d1c7;
  border-radius: 8px;
  background: #f4faf7;
  color: #244f43;
  font-weight: 700;
}

.task-box {
  margin: 12px 0;
  padding: 10px;
  border-left: 4px solid var(--water);
  border-radius: 0 8px 8px 0;
  background: var(--surface-2);
}

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

.btn {
  border: 1px solid #8ba49a;
  border-radius: 8px;
  padding: 9px 12px;
  color: var(--ink);
  background: #ffffff;
  cursor: pointer;
  font-weight: 700;
}

.btn:hover {
  border-color: #36554c;
}

.btn:disabled {
  cursor: not-allowed;
  opacity: 0.55;
}

.btn:focus-visible,
input:focus-visible,
select:focus-visible,
textarea:focus-visible {
  outline: 3px solid rgba(245, 155, 99, 0.65);
  outline-offset: 2px;
}

.btn.primary {
  border-color: #155f4a;
  color: #ffffff;
  background: #155f4a;
}

.control {
  display: grid;
  gap: 6px;
  margin-top: 12px;
}

.control span,
.question-block > span {
  font-weight: 700;
}

output {
  color: var(--water-dark);
  font-weight: 800;
}

input[type="range"] {
  width: 100%;
  accent-color: var(--heat);
}

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

select {
  padding: 9px 10px;
}

textarea {
  margin-top: 8px;
  padding: 10px;
  resize: vertical;
  min-height: 92px;
}

.taxa-row {
  display: grid;
  grid-template-columns: minmax(130px, 1fr) minmax(120px, 180px) 48px;
  gap: 8px;
  align-items: center;
  margin-top: 10px;
}

meter {
  width: 100%;
  height: 16px;
}

.explain-panel {
  margin-top: 10px;
  padding: 14px;
}

.explain-panel h2 {
  font-size: 1.18rem;
}

.explain-panel p {
  margin: 8px 0 0;
  line-height: 1.45;
}

.concept-bullets {
  margin: 10px 0 0;
  padding-left: 20px;
  color: var(--ink);
}

.concept-bullets li {
  margin-top: 6px;
  line-height: 1.35;
}

.trial-log,
.checkpoint,
.model-notes,
.misconceptions,
.challenge-panel {
  margin-top: 14px;
  padding: 14px;
}

.page-nav {
  order: 1;
  display: flex;
  gap: 8px;
  align-items: center;
  margin-bottom: 14px;
  margin-top: 0;
  padding: 10px;
}

.page-panel {
  order: 2;
  padding: 14px;
}

.tab-btn {
  border: 1px solid #8ba49a;
  border-radius: 8px;
  padding: 9px 13px;
  color: var(--ink);
  background: #ffffff;
  cursor: pointer;
  font-weight: 800;
}

.tab-btn.active {
  border-color: #155f4a;
  color: #ffffff;
  background: #155f4a;
}

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

.unlock-status {
  order: 1;
  margin: -4px 14px 4px;
  color: #4e5f58;
  font-weight: 700;
}

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

.tab-panel > :first-child {
  margin-top: 0;
}

.lab-tools {
  display: grid;
  grid-template-columns: minmax(0, 1.4fr) minmax(280px, 0.6fr);
  gap: 14px;
  margin-top: 14px;
}

.trial-header {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  align-items: center;
}

.trial-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.evidence-summary {
  margin: 10px 0 0;
  color: var(--muted);
  font-weight: 700;
}

.table-wrap {
  margin-top: 12px;
  overflow-x: auto;
}

table {
  width: 100%;
  min-width: 760px;
  border-collapse: collapse;
}

th,
td {
  border-bottom: 1px solid var(--line);
  padding: 10px;
  text-align: left;
  vertical-align: top;
}

th {
  background: var(--surface-2);
  color: #31584c;
  font-size: 0.84rem;
  text-transform: uppercase;
}

td {
  line-height: 1.35;
}

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

.misconception-grid article {
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 12px;
  background: #fbfdfc;
}

.misconception-grid h3 {
  margin: 0;
  font-size: 1rem;
}

.misconception-grid p {
  margin: 8px 0 0;
  line-height: 1.4;
}

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

.assessment-grid {
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.question-block {
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 12px;
  background: #fbfdfc;
}

fieldset.question-block {
  margin: 0;
}

legend {
  padding: 0;
  font-weight: 700;
}

.question-block label {
  display: block;
  margin-top: 10px;
  line-height: 1.35;
}

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

.feedback {
  margin: 0;
  font-weight: 700;
}

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

.feedback.needs-work {
  color: var(--gold);
}

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

.challenge-warn {
  color: var(--gold);
}

details summary {
  cursor: pointer;
  font-weight: 800;
}

.notes-grid {
  display: grid;
  grid-template-columns: minmax(260px, 420px) minmax(0, 1fr);
  gap: 14px;
  align-items: start;
  margin-top: 12px;
}

figure {
  margin: 0;
}

figure img {
  display: block;
  width: 100%;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #e9f3f0;
}

figcaption {
  margin-top: 6px;
  font-size: 0.88rem;
}

.lesson-intro {
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 16px;
  background: var(--surface);
}

.lesson-intro h2 {
  font-size: 1.45rem;
}

.lesson-intro p,
.lesson-grid p {
  color: var(--muted);
  line-height: 1.5;
}

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

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

.lesson-grid article {
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 14px;
  background: var(--surface);
}

.lesson-grid h2 {
  font-size: 1.05rem;
}

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

@media (max-width: 1080px) {
  .topbar,
  .lab-shell,
  .lab-tools,
  .site-readouts,
  .community-impact-grid,
  .concept-strip,
  .lesson-grid,
  .misconception-grid,
  .notes-grid {
    grid-template-columns: 1fr;
  }

  .control-panel {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (max-width: 760px) {
  .app {
    padding: 12px;
  }

  .page-nav {
    align-items: stretch;
    flex-direction: column;
  }

  .tab-btn {
    width: 100%;
  }

  h1 {
    font-size: 1.7rem;
  }

  #riverCanvas {
    min-height: 360px;
    height: 54vh;
  }

  .site-readouts,
  .control-panel,
  .checkpoint-grid {
    grid-template-columns: 1fr;
  }

  .trial-header {
    align-items: stretch;
    flex-direction: column;
  }

  .taxa-row {
    grid-template-columns: 1fr;
  }

  .checkpoint-actions {
    grid-column: auto;
  }
}