:root {
  --page-bg: #eef5f7;
  --panel-bg: #ffffff;
  --ink: #18313e;
  --muted: #58707d;
  --border: #c9d9df;
  --accent: #176b87;
  --accent-dark: #0f536a;
  --accent-soft: #dceff5;
  --success: #2f7b4b;
  --success-soft: #e1f2e8;
  --warning: #9a5d19;
  --warning-soft: #fff0d6;
  --error: #9b3939;
  --error-soft: #f8e2e2;
  --shadow: 0 10px 28px rgba(30, 61, 75, 0.1);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-width: 320px;
  background: var(--page-bg);
  color: var(--ink);
  font-family:
    Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI",
    sans-serif;
  line-height: 1.5;
}

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

button {
  cursor: pointer;
}

button:disabled,
select:disabled {
  cursor: not-allowed;
  opacity: 0.55;
}

.site-header {
  padding: 46px 24px 30px;
  background: #123e50;
  color: #ffffff;
}

.header-inner,
main,
footer {
  width: min(1180px, calc(100% - 32px));
  margin-inline: auto;
}

.eyebrow,
.step-label {
  margin: 0 0 6px;
  color: #88d0e5;
  font-size: 0.78rem;
  font-weight: 800;
  letter-spacing: 0.11em;
  text-transform: uppercase;
}

.site-header h1 {
  margin: 0;
  font-size: clamp(2rem, 5vw, 3.5rem);
  line-height: 1.05;
}

.subtitle {
  max-width: 790px;
  margin: 16px 0 0;
  color: #d9edf3;
  font-size: 1.05rem;
}

.route-chip {
  display: inline-block;
  margin: 16px 0 0;
  padding: 7px 12px;
  border: 1px solid rgba(255, 255, 255, 0.3);
  border-radius: 999px;
  color: #ffffff;
  font-size: 0.9rem;
  font-weight: 800;
}

main {
  padding: 30px 0 50px;
}

.investigation-grid {
  display: grid;
  grid-template-columns: minmax(0, 1.05fr) minmax(0, 0.95fr);
  gap: 22px;
  align-items: start;
}

.panel {
  margin-bottom: 22px;
  padding: 24px;
  border: 1px solid var(--border);
  border-radius: 18px;
  background: var(--panel-bg);
  box-shadow: var(--shadow);
}

.panel-heading {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 10px;
}

.panel h2 {
  margin: 0;
  font-size: 1.35rem;
}

.instructions {
  margin: 0 0 18px;
  color: var(--muted);
}

.status-chip {
  flex: 0 0 auto;
  padding: 7px 11px;
  border-radius: 999px;
  background: var(--accent-soft);
  color: var(--accent-dark);
  font-size: 0.82rem;
  font-weight: 800;
}

.ocean-stage,
.graph-wrap {
  overflow: hidden;
  border: 1px solid var(--border);
  border-radius: 14px;
  background: #eaf7fb;
}

.ocean-stage svg,
.graph-wrap svg {
  display: block;
  width: 100%;
  height: auto;
  touch-action: none;
}

.location-label {
  fill: #263e34;
  font-size: 12px;
  font-weight: 900;
}

#dragTarget {
  cursor: grab;
}

#dragTarget:active {
  cursor: grabbing;
}

.range-label {
  display: grid;
  gap: 8px;
  margin-top: 16px;
  color: var(--muted);
  font-size: 0.92rem;
  font-weight: 700;
}

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

.button-row,
.label-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 18px;
}

.primary-button,
.secondary-button,
.text-button,
.label-bank button {
  border-radius: 10px;
  font-weight: 800;
}

.primary-button {
  border: 1px solid var(--accent);
  padding: 10px 16px;
  background: var(--accent);
  color: #ffffff;
}

.primary-button:hover:not(:disabled) {
  background: var(--accent-dark);
}

.secondary-button {
  border: 1px solid var(--border);
  padding: 10px 16px;
  background: #ffffff;
  color: var(--ink);
}

.secondary-button:hover:not(:disabled),
.label-bank button:hover:not(:disabled) {
  border-color: var(--accent);
  background: var(--accent-soft);
}

.text-button {
  border: 0;
  padding: 7px 0;
  background: transparent;
  color: var(--accent-dark);
}

.reading-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 10px;
  margin-top: 18px;
}

.reading-grid > div {
  padding: 12px;
  border: 1px solid var(--border);
  border-radius: 12px;
  background: #f7fafb;
}

.reading-grid span {
  display: block;
  color: var(--muted);
  font-size: 0.78rem;
  font-weight: 700;
  text-transform: uppercase;
}

.reading-grid strong {
  display: block;
  margin-top: 2px;
  font-size: 1.08rem;
}

.grid-lines line {
  stroke: #cbdde4;
  stroke-width: 1;
}

.grid-lines line:first-child,
.grid-lines line:nth-child(2) {
  stroke: #617986;
  stroke-width: 2;
}

.axis-labels {
  fill: #546d79;
  font-size: 13px;
  font-weight: 600;
}

.graph-location {
  fill: var(--ink);
  font-size: 13px;
  font-weight: 900;
}

#depthLine {
  color: var(--accent);
}

.graph-prompt {
  fill: #6a808a;
  font-size: 16px;
  font-weight: 700;
}

.measurement-dot {
  fill: #fff3a6;
  stroke: #5f5120;
  stroke-width: 2;
}

.graph-point {
  fill: var(--accent);
}

.label-bank {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.label-bank button {
  border: 1px solid var(--border);
  padding: 9px 13px;
  background: #ffffff;
  color: var(--ink);
}

.label-bank button.active {
  border-color: var(--accent);
  background: var(--accent);
  color: #ffffff;
}

.label-bank button.placed {
  border-color: var(--success);
  background: var(--success-soft);
  color: #215c38;
}

.feedback {
  margin-top: 16px;
  padding: 13px 15px;
  border-radius: 12px;
  background: #f3f7f8;
  color: var(--muted);
  font-weight: 700;
}

.feedback.success {
  background: var(--success-soft);
  color: var(--success);
}

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

.feedback.error {
  background: var(--error-soft);
  color: var(--error);
}

.student-label text {
  font-size: 12px;
  font-weight: 800;
  pointer-events: none;
}

.student-label rect,
.student-label line {
  pointer-events: none;
}

.student-label.correct rect {
  fill: var(--success-soft);
  stroke: var(--success);
}

.student-label.incorrect rect {
  fill: var(--error-soft);
  stroke: var(--error);
}

.student-label.unchecked rect {
  fill: #ffffff;
  stroke: var(--accent);
}

.motion-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 16px;
}

.motion-card {
  padding: 18px;
  border: 1px solid var(--border);
  border-radius: 14px;
  background: #f8fbfc;
}

.motion-card h3 {
  margin: 0;
  font-size: 1.05rem;
}

.motion-card > p {
  margin: 6px 0 16px;
  color: var(--muted);
}

.plate-diagram {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto minmax(0, 1fr);
  align-items: center;
  gap: 8px;
  margin-bottom: 16px;
}

.plate-block {
  padding: 12px 8px;
  border: 2px solid #6c7f88;
  border-radius: 9px;
  background: #e7eef1;
  text-align: center;
  font-size: 0.88rem;
  font-weight: 800;
}

.boundary-symbol {
  min-width: 64px;
  padding: 8px;
  border-radius: 8px;
  background: var(--accent-soft);
  color: var(--accent-dark);
  text-align: center;
  font-size: 0.78rem;
  font-weight: 900;
}

.ridge-symbol {
  border-bottom: 4px solid var(--accent);
}

.trench-symbol {
  border-top: 4px solid var(--accent);
}

.motion-select-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
}

.motion-select-grid label {
  color: var(--ink);
  font-weight: 750;
}

.motion-select-grid select {
  width: 100%;
  margin-top: 7px;
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 10px;
  background: #ffffff;
  color: var(--ink);
}

.motion-select-grid select.correct {
  border-color: var(--success);
  background: var(--success-soft);
}

.motion-select-grid select.incorrect {
  border-color: var(--error);
  background: var(--error-soft);
}

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

.question-grid label {
  color: var(--ink);
  font-weight: 750;
}

textarea {
  width: 100%;
  margin-top: 8px;
  resize: vertical;
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 12px;
  background: #fbfdfd;
  color: var(--ink);
}

.model-note {
  margin: 18px 0 0;
  padding-top: 15px;
  border-top: 1px solid var(--border);
  color: var(--muted);
  font-size: 0.88rem;
}

textarea:focus,
select:focus,
button:focus-visible,
input:focus-visible,
#dragTarget:focus-visible {
  outline: 3px solid rgba(23, 107, 135, 0.32);
  outline-offset: 2px;
}

footer {
  padding: 0 0 38px;
  color: var(--muted);
  text-align: center;
}

@media (max-width: 900px) {
  .investigation-grid,
  .motion-grid {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 650px) {
  .question-grid,
  .motion-select-grid {
    grid-template-columns: 1fr;
  }

  .plate-diagram {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 560px) {
  .site-header {
    padding: 34px 18px 24px;
  }

  .header-inner,
  main,
  footer {
    width: min(100% - 20px, 1180px);
  }

  .panel {
    padding: 17px;
    border-radius: 14px;
  }

  .panel-heading {
    align-items: stretch;
    flex-direction: column;
    gap: 8px;
  }

  .status-chip {
    align-self: flex-start;
  }

  .reading-grid {
    grid-template-columns: 1fr;
  }

  .button-row > button,
  .label-actions > button {
    width: 100%;
  }

  .label-bank {
    display: grid;
    grid-template-columns: 1fr;
  }
}