:root {
  --bg: #0b1220;
  --panel: #121a2b;
  --panel-2: #182338;
  --text: #e8eefc;
  --muted: #9aa8c7;
  --accent: #5b9dff;
  --accent-2: #3dd6c6;
  --good: #3ecf8e;
  --warn: #f0c14b;
  --bad: #ff6b7a;
  --humid: #7ecbff;
  --dry: #6b8cae;
  --hot: #ff9f6b;
  --border: rgba(255, 255, 255, 0.08);
  --shadow: 0 18px 50px rgba(0, 0, 0, 0.35);
  --radius: 16px;
  font-family: "Segoe UI", system-ui, -apple-system, sans-serif;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  min-height: 100vh;
  color: var(--text);
  background:
    radial-gradient(1200px 600px at 10% -10%, rgba(91, 157, 255, 0.16), transparent 55%),
    radial-gradient(900px 500px at 100% 0%, rgba(61, 214, 198, 0.1), transparent 50%),
    var(--bg);
}

.app {
  max-width: 1100px;
  margin: 0 auto;
  padding: 1.5rem 1.25rem 3rem;
}

.header h1 {
  margin: 0.2rem 0 0.5rem;
  font-size: clamp(1.5rem, 3vw, 2rem);
  letter-spacing: -0.02em;
}

.eyebrow {
  margin: 0;
  color: var(--accent-2);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  font-size: 0.75rem;
  font-weight: 700;
}

.banner {
  margin: 0.75rem 0 0;
  padding: 0.65rem 0.85rem;
  border-radius: 10px;
  border: 1px solid rgba(240, 193, 75, 0.35);
  background: rgba(240, 193, 75, 0.08);
  color: var(--warn);
  font-size: 0.88rem;
  line-height: 1.4;
}

.disclaimer {
  color: var(--muted);
  line-height: 1.5;
  margin: 0.5rem 0 0;
  font-size: 0.9rem;
}

.disclaimer a { color: var(--accent); }

/* Intro / primer before the interactive lab */
.primer {
  margin-top: 1.25rem;
}

.primer-head {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 1rem;
  margin-bottom: 0.35rem;
}

.primer-head h2 {
  margin: 0;
  font-size: 1.2rem;
  letter-spacing: -0.02em;
}

.primer-toggle {
  flex-shrink: 0;
  font-size: 0.8rem;
  color: var(--muted);
  padding: 0.35rem 0.65rem;
}

.primer-toggle:hover {
  color: var(--text);
  border-color: rgba(91, 157, 255, 0.35);
}

.primer.collapsed #primerBody {
  display: none;
}

.primer.collapsed .primer-head {
  margin-bottom: 0;
}

.primer-lead {
  margin: 0.5rem 0 1rem;
  color: var(--text);
  line-height: 1.55;
  font-size: 0.98rem;
}

.primer-lead strong {
  color: var(--accent-2);
}

.primer-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0.75rem;
  margin-bottom: 1rem;
}

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

.primer-card {
  background: rgba(0, 0, 0, 0.22);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 0.85rem 0.95rem;
}

.primer-card h3 {
  margin: 0 0 0.45rem;
  font-size: 0.95rem;
  color: var(--accent);
}

.primer-card p,
.primer-card li {
  margin: 0;
  color: var(--muted);
  font-size: 0.86rem;
  line-height: 1.5;
}

.primer-card ul {
  margin: 0 0 0.55rem;
  padding-left: 1.15rem;
}

.primer-card li {
  margin-bottom: 0.3rem;
}

.primer-card li strong {
  color: var(--text);
}

.primer-note {
  margin-top: 0.5rem !important;
  padding-top: 0.5rem;
  border-top: 1px solid var(--border);
  font-size: 0.82rem !important;
  color: var(--humid) !important;
}

.primer-how-title {
  margin: 0.25rem 0 0.4rem;
  font-size: 1rem;
}

.primer > #primerBody > p {
  margin: 0 0 0.75rem;
  color: var(--muted);
  line-height: 1.5;
  font-size: 0.92rem;
}

.primer-steps {
  margin: 0 0 1rem;
  padding-left: 1.25rem;
  color: var(--muted);
  font-size: 0.9rem;
  line-height: 1.5;
}

.primer-steps li {
  margin-bottom: 0.55rem;
}

.primer-steps strong {
  color: var(--text);
}

.primer-tip {
  margin: 0 0 0.75rem !important;
  padding: 0.7rem 0.85rem;
  border-radius: 10px;
  border-left: 3px solid var(--accent-2);
  background: rgba(61, 214, 198, 0.07);
  color: var(--muted) !important;
  font-size: 0.88rem !important;
  line-height: 1.5 !important;
}

.primer-tip strong {
  color: var(--accent-2);
}

.primer-sources {
  margin: 0 0 0.5rem !important;
  font-size: 0.82rem !important;
  color: var(--muted) !important;
  line-height: 1.45 !important;
}

.primer-jump {
  margin: 0.75rem 0 0 !important;
}

.primer-jump a {
  color: var(--accent);
  font-weight: 600;
  font-size: 0.9rem;
  text-decoration: none;
}

.primer-jump a:hover {
  text-decoration: underline;
}

.tabs {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-top: 1.25rem;
  scroll-margin-top: 1rem;
}

.tab {
  border: 1px solid var(--border);
  background: var(--panel);
  color: var(--muted);
  border-radius: 999px;
  padding: 0.5rem 1rem;
  cursor: pointer;
  font: inherit;
  font-weight: 600;
  font-size: 0.9rem;
}

.tab:hover { color: var(--text); border-color: rgba(91, 157, 255, 0.4); }
.tab.active {
  color: #061018;
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  border-color: transparent;
}

.mode { display: none; margin-top: 1rem; }
.mode.active { display: block; }

.panel {
  background: linear-gradient(180deg, var(--panel), var(--panel-2));
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 1.1rem 1.2rem 1.25rem;
}

.panel h2 {
  margin: 0 0 0.35rem;
  font-size: 1.1rem;
}

.panel .sub {
  margin: 0 0 1rem;
  color: var(--muted);
  font-size: 0.88rem;
  line-height: 1.45;
}

.grid-2 {
  display: grid;
  gap: 1rem;
  grid-template-columns: 1fr 1fr;
}

.grid-3 {
  display: grid;
  gap: 1rem;
  grid-template-columns: 1.1fr 0.9fr 1fr;
}

@media (max-width: 900px) {
  .grid-2, .grid-3 { grid-template-columns: 1fr; }
}

label.ctrl {
  display: grid;
  gap: 0.3rem;
  font-size: 0.82rem;
  color: var(--muted);
  margin-bottom: 0.75rem;
}

label.ctrl strong {
  color: var(--text);
  font-weight: 600;
  font-variant-numeric: tabular-nums;
}

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

select, button, input[type="number"] {
  font: inherit;
}

select, input[type="number"] {
  background: #0d1524;
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 0.45rem 0.6rem;
}

button {
  cursor: pointer;
  border-radius: 10px;
  border: 1px solid var(--border);
  background: #0d1524;
  color: var(--text);
  padding: 0.5rem 0.85rem;
  font-weight: 600;
}

button.primary {
  background: linear-gradient(135deg, var(--accent), #3d7fe0);
  border: none;
  color: #fff;
}

button.ghost { background: transparent; }

.presets {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin: 0.5rem 0 1rem;
}

.presets button {
  font-size: 0.78rem;
  padding: 0.35rem 0.65rem;
  border-radius: 999px;
}

.presets button.active {
  border-color: var(--accent-2);
  color: var(--accent-2);
}

.toggle-row {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin: 0.5rem 0 0.75rem;
  font-size: 0.88rem;
  color: var(--muted);
}

.toggle-row input { accent-color: var(--accent-2); }

/* Molecule canvas */
.mol-wrap {
  position: relative;
  border-radius: 12px;
  border: 1px solid var(--border);
  background: #0a101c;
  overflow: hidden;
  height: 220px;
}

.mol-badge {
  position: absolute;
  top: 0.45rem;
  right: 0.45rem;
  z-index: 2;
  font-size: 0.68rem;
  font-weight: 700;
  letter-spacing: 0.03em;
  text-transform: uppercase;
  color: var(--warn);
  background: rgba(11, 18, 32, 0.85);
  border: 1px solid rgba(240, 193, 75, 0.4);
  border-radius: 6px;
  padding: 0.25rem 0.45rem;
  pointer-events: none;
}

#molCanvas {
  width: 100%;
  height: 100%;
  display: block;
  opacity: 0.88; /* decoration under mass % truth */
}

.mol-legend {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin-top: 0.6rem;
  font-size: 0.78rem;
  color: var(--muted);
}

.stat-primary {
  grid-column: 1 / -1;
  border-color: rgba(61, 214, 198, 0.35) !important;
  background: rgba(61, 214, 198, 0.06) !important;
}

.stat-primary .v {
  font-size: 1.45rem !important;
}

.stat-hint {
  margin-top: 0.25rem;
  font-size: 0.72rem;
  color: var(--muted);
}

.mol-legend span::before {
  content: "";
  display: inline-block;
  width: 0.55rem;
  height: 0.55rem;
  border-radius: 50%;
  margin-right: 0.3rem;
  vertical-align: middle;
}

.mol-legend .dry::before { background: var(--dry); }
.mol-legend .h2o::before { background: var(--humid); }

.stat-row {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 0.5rem;
  margin-top: 0.75rem;
}

.stat {
  background: rgba(0, 0, 0, 0.22);
  border-radius: 10px;
  padding: 0.55rem 0.65rem;
  border: 1px solid var(--border);
}

.stat .k {
  font-size: 0.72rem;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.stat .v {
  font-size: 1.15rem;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
  margin-top: 0.15rem;
}

.stat .v.hot { color: var(--hot); }
.stat .v.humid { color: var(--humid); }
.stat .v.good { color: var(--good); }

/* Altitude tape */
.tape {
  position: relative;
  height: 280px;
  border-radius: 12px;
  border: 1px solid var(--border);
  background:
    linear-gradient(180deg, rgba(255, 159, 107, 0.12), transparent 40%),
    linear-gradient(180deg, #0a101c, #121a2b);
  overflow: hidden;
}

.tape-scale {
  position: absolute;
  inset: 0;
  background-image: repeating-linear-gradient(
    to bottom,
    transparent,
    transparent 27px,
    rgba(255, 255, 255, 0.04) 27px,
    rgba(255, 255, 255, 0.04) 28px
  );
}

.marker {
  position: absolute;
  left: 8%;
  right: 8%;
  height: 2px;
  transform: translateY(-50%);
  transition: top 0.25s ease;
}

.marker::after {
  content: attr(data-label);
  position: absolute;
  left: 0;
  top: -1.1rem;
  font-size: 0.72rem;
  font-weight: 700;
  white-space: nowrap;
}

.marker.elev { background: var(--muted); }
.marker.elev::after { color: var(--muted); }
.marker.pa { background: var(--accent); }
.marker.pa::after { color: var(--accent); }
.marker.da-dry { background: var(--hot); }
.marker.da-dry::after { color: var(--hot); }
.marker.da-hum { background: var(--humid); height: 3px; }
.marker.da-hum::after { color: var(--humid); }

.tape-caption {
  margin-top: 0.6rem;
  font-size: 0.85rem;
  color: var(--muted);
  line-height: 1.45;
}

.callout {
  margin-top: 0.75rem;
  padding: 0.7rem 0.8rem;
  border-radius: 10px;
  background: rgba(91, 157, 255, 0.08);
  border: 1px solid rgba(91, 157, 255, 0.22);
  font-size: 0.84rem;
  line-height: 1.45;
  color: var(--muted);
}

.callout strong { color: var(--text); }

/* Mission theater */
.runway-scene {
  position: relative;
  height: 200px;
  border-radius: 12px;
  border: 1px solid var(--border);
  background: linear-gradient(180deg, #1a2740 0%, #1a2740 48%, #2a3344 48%, #3d4658 100%);
  overflow: hidden;
}

.runway-scene.grass .strip { background: #3a4a32; }
.runway-scene.soft .strip { background: #4a4030; }

.sky-label {
  position: absolute;
  top: 0.5rem;
  left: 0.75rem;
  font-size: 0.75rem;
  color: var(--muted);
}

.strip {
  position: absolute;
  left: 5%;
  right: 5%;
  bottom: 28%;
  height: 18px;
  background: #555e6e;
  border-radius: 2px;
}

.strip::before {
  content: "";
  position: absolute;
  inset: 7px 10% auto;
  height: 2px;
  background: repeating-linear-gradient(
    90deg,
    #fff 0 12px,
    transparent 12px 22px
  );
  opacity: 0.5;
}

.roll-bar {
  position: absolute;
  left: 5%;
  bottom: 28%;
  height: 18px;
  background: linear-gradient(90deg, rgba(255, 107, 122, 0.85), rgba(255, 159, 107, 0.9));
  border-radius: 2px 0 0 2px;
  transition: width 0.3s ease;
  min-width: 4px;
}

.roll-bar.margin {
  background: linear-gradient(90deg, rgba(240, 193, 75, 0.5), rgba(240, 193, 75, 0.75));
  opacity: 0.7;
}

.plane {
  position: absolute;
  bottom: 36%;
  font-size: 1.4rem;
  transition: left 0.3s ease;
  filter: drop-shadow(0 2px 4px rgba(0, 0, 0, 0.4));
}

.wind-arrow {
  position: absolute;
  top: 2.2rem;
  right: 0.75rem;
  font-size: 0.8rem;
  color: var(--accent-2);
  font-weight: 700;
}

.climb-wedge {
  position: absolute;
  left: 5%;
  bottom: 46%;
  width: 0;
  height: 0;
  border-style: solid;
  opacity: 0.85;
  transition: border-width 0.3s ease;
}

.obstacle {
  position: absolute;
  right: 12%;
  bottom: 46%;
  width: 8px;
  height: 36px;
  background: #ff6b7a;
  border-radius: 2px 2px 0 0;
}

.meters {
  display: grid;
  gap: 0.55rem;
  margin-top: 0.85rem;
}

.meter label {
  display: flex;
  justify-content: space-between;
  font-size: 0.78rem;
  color: var(--muted);
  margin-bottom: 0.2rem;
}

.meter .bar {
  height: 10px;
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.06);
  overflow: hidden;
}

.meter .fill {
  height: 100%;
  border-radius: 999px;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  transition: width 0.25s ease;
}

.verdict {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  margin-top: 0.75rem;
  padding: 0.45rem 0.75rem;
  border-radius: 999px;
  font-weight: 800;
  font-size: 0.85rem;
  letter-spacing: 0.04em;
}

.verdict.ok { background: rgba(62, 207, 142, 0.15); color: var(--good); }
.verdict.marginal { background: rgba(240, 193, 75, 0.15); color: var(--warn); }
.verdict.no { background: rgba(255, 107, 122, 0.15); color: var(--bad); }

.teach {
  margin-top: 0.85rem;
  padding: 0.7rem 0.8rem;
  border-left: 3px solid var(--accent-2);
  background: rgba(61, 214, 198, 0.06);
  font-size: 0.86rem;
  color: var(--muted);
  line-height: 1.45;
}

/* Guide */
.story-card {
  padding: 1rem;
  border-radius: 12px;
  border: 1px solid var(--border);
  background: rgba(0, 0, 0, 0.2);
  margin-bottom: 1rem;
}

.story-card h3 { margin: 0 0 0.4rem; }
.story-card p { margin: 0; color: var(--muted); line-height: 1.5; font-size: 0.92rem; }

.story-nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  align-items: center;
  margin-bottom: 1rem;
}

.story-nav .step-ind {
  margin-left: auto;
  color: var(--muted);
  font-size: 0.85rem;
}

.quiz-q {
  margin-top: 1rem;
}

.quiz-q .prompt {
  font-weight: 600;
  margin-bottom: 0.6rem;
}

.choices {
  display: grid;
  gap: 0.4rem;
}

.choices button {
  text-align: left;
  line-height: 1.35;
  font-weight: 500;
}

.choices button.correct {
  border-color: var(--good);
  background: rgba(62, 207, 142, 0.12);
}

.choices button.wrong {
  border-color: var(--bad);
  background: rgba(255, 107, 122, 0.1);
}

.explain {
  margin-top: 0.6rem;
  font-size: 0.86rem;
  color: var(--muted);
  line-height: 1.45;
}

.about-list {
  margin: 0.5rem 0 0;
  padding-left: 1.2rem;
  color: var(--muted);
  font-size: 0.88rem;
  line-height: 1.5;
}

.about-list li { margin-bottom: 0.35rem; }

.hidden { display: none !important; }

footer.note {
  margin-top: 1.5rem;
  color: var(--muted);
  font-size: 0.8rem;
  line-height: 1.45;
}