:root {
  --bg:          #0a0b10;
  --bg-elev:     #12141b;
  --bg-elev-2:   #1a1d26;
  --panel:       #12141b;
  --panel-2:     #161922;
  --text:        #e7e9ef;
  --muted:       #8a8f9e;
  --dim:         #5c6270;
  --border:      rgba(255, 255, 255, 0.06);
  --border-mid:  rgba(255, 255, 255, 0.09);
  --border-strong: rgba(255, 255, 255, 0.14);
  --accent:      #22d3ee;
  --accent-dim:  rgba(34, 211, 238, 0.15);
  --earth:       #60a5fa;
  --mars:        #f87171;
  --moon:        #e5e7eb;
  --ring:        rgba(34, 211, 238, 0.35);
  --shadow-sm:   0 1px 2px rgba(0, 0, 0, 0.5);
  --shadow-md:   0 6px 20px rgba(0, 0, 0, 0.35);
  --shadow-lg:   0 16px 40px rgba(0, 0, 0, 0.4);
}

* { box-sizing: border-box; }

html, body {
  margin: 0; padding: 0;
  color: var(--text);
  font-family: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  min-height: 100vh;
  background: var(--bg);
  overflow-x: hidden;
  font-feature-settings: "cv11", "ss01";
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body::before {
  content: "";
  position: fixed; inset: 0;
  background:
    radial-gradient(ellipse 70% 50% at 0% 0%, rgba(99, 102, 241, 0.07), transparent 60%),
    radial-gradient(ellipse 50% 40% at 100% 0%, rgba(239, 68, 68, 0.05), transparent 60%);
  z-index: -1;
  pointer-events: none;
}

/* ---------- Header ---------- */
header {
  padding: 36px 48px 0;
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  gap: 24px;
  flex-wrap: wrap;
  border-bottom: 1px solid var(--border);
  padding-bottom: 20px;
}

.title-block h1 {
  margin: 0;
  font-size: 22px;
  font-weight: 600;
  letter-spacing: -0.01em;
  color: var(--text);
  display: inline-flex;
  align-items: center;
  gap: 10px;
}
.title-block h1::before {
  content: "";
  display: inline-block;
  width: 6px; height: 6px;
  border-radius: 50%;
  background: var(--accent);
  box-shadow: 0 0 8px var(--accent);
}
.subtitle {
  margin: 6px 0 0;
  color: var(--muted);
  font-size: 13px;
  font-weight: 400;
  letter-spacing: 0.01em;
}

.planet-chips { display: flex; gap: 8px; }
.chip {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 5px 11px;
  background: var(--panel);
  border: 1px solid var(--border-mid);
  border-radius: 6px;
  font-size: 11.5px;
  color: var(--muted);
  font-weight: 500;
  letter-spacing: 0.01em;
}
.chip .orb {
  width: 8px; height: 8px;
  border-radius: 50%;
  display: inline-block;
}
.chip.earth .orb { background: var(--earth); }
.chip.mars  .orb { background: var(--mars); }
.chip.moon  .orb { background: var(--moon); }

/* ---------- Tabs ---------- */
.tabs {
  display: flex;
  gap: 0;
  padding: 0 48px;
  border-bottom: 1px solid var(--border);
  background: var(--bg);
}
.tab {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: transparent;
  border: none;
  border-bottom: 2px solid transparent;
  color: var(--muted);
  padding: 14px 20px 13px;
  border-radius: 0;
  font-weight: 500;
  font-size: 13.5px;
  letter-spacing: 0.01em;
  cursor: pointer;
  transition: color 0.12s ease, border-color 0.12s ease;
  box-shadow: none;
  margin-right: 4px;
}
.tab:hover {
  color: var(--text);
  background: transparent;
  filter: none;
}
.tab.active {
  color: var(--text);
  border-bottom-color: var(--accent);
  background: transparent;
}
.tab.active .tab-icon { color: var(--accent); }
.tab-icon { font-size: 14px; line-height: 1; color: var(--dim); }

/* ---------- Layout ---------- */
main.mode {
  display: grid;
  grid-template-columns: 320px 1fr;
  gap: 20px;
  padding: 24px 48px 48px;
}
main.mode[hidden] { display: none; }

.canvas-wrap, .stats, .explainer, .energy-panel {
  grid-column: 2;
}

/* ---------- Controls panel ---------- */
.controls {
  grid-row: 1 / span 5;
  background: var(--panel);
  border: 1px solid var(--border-mid);
  border-radius: 10px;
  padding: 20px;
  height: fit-content;
  position: sticky;
  top: 20px;
  box-shadow: var(--shadow-sm);
  z-index: 20;
}

.panel-title {
  font-size: 10.5px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--muted);
  margin: 0 0 16px;
}

.control-group {
  display: flex;
  flex-direction: column;
  gap: 16px;
  padding-bottom: 18px;
  margin-bottom: 18px;
  border-bottom: 1px solid var(--border);
}
.control-group:last-child { border-bottom: none; margin-bottom: 0; padding-bottom: 0; }

.group-label {
  color: var(--muted);
  font-size: 10.5px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.1em;
}

label.slider {
  display: flex;
  flex-direction: column;
  gap: 8px;
  font-size: 12.5px;
  color: var(--muted);
  font-weight: 400;
}
.slider-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 8px;
}
.slider-label {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  color: var(--text);
  font-weight: 500;
}
.slider-value {
  color: var(--text);
  font-weight: 600;
  font-size: 13px;
  font-variant-numeric: tabular-nums;
  font-family: "JetBrains Mono", monospace;
  background: none;
  -webkit-text-fill-color: currentColor;
}

/* Range slider */
input[type="range"] {
  -webkit-appearance: none; appearance: none;
  width: 100%;
  height: 4px;
  border-radius: 2px;
  background: linear-gradient(
    to right,
    var(--accent) 0%,
    var(--accent) var(--fill, 40%),
    rgba(255, 255, 255, 0.08) var(--fill, 40%),
    rgba(255, 255, 255, 0.08) 100%
  );
  outline: none;
  cursor: pointer;
}
input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none; appearance: none;
  width: 14px; height: 14px;
  border-radius: 50%;
  background: var(--text);
  border: 0;
  cursor: grab;
  box-shadow: 0 0 0 0 var(--ring), 0 1px 3px rgba(0, 0, 0, 0.5);
  transition: box-shadow 0.15s ease;
}
input[type="range"]::-webkit-slider-thumb:hover {
  box-shadow: 0 0 0 5px var(--ring), 0 1px 3px rgba(0, 0, 0, 0.5);
}
input[type="range"]::-webkit-slider-thumb:active {
  cursor: grabbing;
  box-shadow: 0 0 0 7px var(--ring), 0 1px 3px rgba(0, 0, 0, 0.5);
}
input[type="range"]::-moz-range-thumb {
  width: 14px; height: 14px;
  border-radius: 50%;
  background: var(--text);
  border: 0;
  cursor: grab;
}

/* Info tooltip */
.info {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 14px; height: 14px;
  border-radius: 50%;
  background: rgba(255, 255, 255, 0.05);
  border: 1px solid var(--border-strong);
  color: var(--muted);
  font-size: 9px;
  font-weight: 700;
  cursor: help;
  position: relative;
  outline: none;
  transition: color 0.12s, background 0.12s, border-color 0.12s;
}
.info::before {
  content: "i";
  font-style: italic;
  line-height: 1;
}
.info:hover, .info:focus {
  color: var(--accent);
  background: var(--accent-dim);
  border-color: var(--accent);
}
.info::after {
  content: attr(data-tip);
  position: absolute;
  top: calc(100% + 8px);
  left: -6px;
  width: 260px;
  max-width: 85vw;
  background: var(--bg-elev-2);
  color: var(--text);
  font-size: 11.5px;
  font-weight: 400;
  line-height: 1.55;
  letter-spacing: 0.005em;
  padding: 10px 12px;
  border-radius: 6px;
  border: 1px solid var(--border-strong);
  box-shadow: var(--shadow-lg);
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.12s ease, transform 0.12s ease;
  transform: translateY(-4px);
  z-index: 100;
  text-align: left;
  white-space: normal;
}
.info:hover::after, .info:focus::after {
  opacity: 1;
  transform: translateY(0);
}

/* Worlds check cards */
.check {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 9px 12px;
  background: var(--bg-elev);
  border: 1px solid var(--border-mid);
  border-radius: 6px;
  cursor: pointer;
  font-size: 12.5px;
  color: var(--text);
  font-weight: 500;
  transition: border-color 0.12s, background 0.12s;
}
.check:hover {
  border-color: var(--border-strong);
  background: var(--panel-2);
}
.check input { margin: 0; accent-color: var(--accent); }
.check .orb {
  width: 8px; height: 8px;
  border-radius: 50%;
}
.check.earth .orb { background: var(--earth); }
.check.mars  .orb { background: var(--mars); }
.check.moon  .orb { background: var(--moon); }

.worlds-grid { display: grid; grid-template-columns: 1fr; gap: 6px; }

/* Buttons */
.buttons { flex-direction: row; gap: 8px; }
button {
  flex: 1;
  background: var(--accent);
  color: #0a1b1e;
  border: 1px solid var(--accent);
  border-radius: 6px;
  padding: 9px 14px;
  font-weight: 600;
  cursor: pointer;
  font-size: 13px;
  letter-spacing: 0.01em;
  transition: background 0.12s, border-color 0.12s, transform 0.05s;
  box-shadow: var(--shadow-sm);
  font-family: inherit;
  display: inline-flex;
  align-items: center;
  justify-content: center;
}
button:hover {
  background: #3ddcee;
  border-color: #3ddcee;
  filter: none;
}
button:active { transform: translateY(1px); }
button.secondary {
  background: transparent;
  color: var(--text);
  border-color: var(--border-strong);
  box-shadow: none;
}
button.secondary:hover {
  background: var(--bg-elev);
  border-color: rgba(255, 255, 255, 0.22);
}
button.full-width { margin-top: 10px; }

/* Advanced collapsible */
details.advanced {
  border-bottom: 1px solid var(--border);
  padding-bottom: 18px;
  margin-bottom: 18px;
}
details.advanced summary {
  cursor: pointer;
  color: var(--muted);
  font-size: 10.5px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  padding: 4px 0;
  list-style: none;
  display: flex;
  align-items: center;
  gap: 6px;
  transition: color 0.12s;
}
details.advanced summary:hover { color: var(--text); }
details.advanced summary::-webkit-details-marker { display: none; }
details.advanced summary::before {
  content: "▸";
  transition: transform 0.15s ease;
  color: var(--dim);
  font-size: 9px;
}
details.advanced[open] summary::before { transform: rotate(90deg); color: var(--accent); }
details.advanced[open] { padding-bottom: 0; }
details.advanced .control-group {
  border-bottom: none;
  padding-bottom: 0;
  margin-bottom: 0;
  padding-top: 14px;
}

/* ---------- Canvas ---------- */
.canvas-wrap {
  background: var(--panel);
  border: 1px solid var(--border-mid);
  border-radius: 10px;
  padding: 14px;
  box-shadow: var(--shadow-sm);
  position: relative;
  overflow: hidden;
}
canvas {
  width: 100%;
  height: auto;
  display: block;
  border-radius: 6px;
}

.legend {
  margin-top: 10px;
  display: flex;
  gap: 18px;
  flex-wrap: wrap;
  color: var(--muted);
  font-size: 11.5px;
  padding: 2px 4px;
  font-variant-numeric: tabular-nums;
}
.legend b { color: var(--text); font-weight: 600; }

/* Live inspector on canvas */
.inspector {
  position: absolute;
  pointer-events: none;
  background: var(--bg-elev-2);
  border: 1px solid var(--border-strong);
  border-radius: 6px;
  padding: 8px 10px;
  font-size: 11px;
  color: var(--text);
  font-variant-numeric: tabular-nums;
  font-family: "JetBrains Mono", monospace;
  box-shadow: var(--shadow-lg);
  opacity: 0;
  transition: opacity 0.1s;
  z-index: 10;
  min-width: 150px;
}
.inspector.visible { opacity: 1; }
.inspector .row {
  display: flex;
  justify-content: space-between;
  gap: 14px;
  line-height: 1.5;
  font-family: "JetBrains Mono", monospace;
}
.inspector .row b { font-weight: 500; }
.inspector .hdr {
  color: var(--muted);
  font-size: 9.5px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 6px;
  font-family: "Inter", sans-serif;
  font-weight: 500;
}
.inspector .earth b { color: var(--earth); }
.inspector .mars  b { color: var(--mars); }
.inspector .moon  b { color: var(--moon); }

/* ---------- Stats ---------- */
.stats {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 12px;
}
.stat-card {
  background: var(--panel);
  border: 1px solid var(--border-mid);
  border-radius: 10px;
  padding: 16px 18px;
  position: relative;
  overflow: hidden;
  box-shadow: var(--shadow-sm);
}
.stat-card::before {
  content: "";
  position: absolute;
  top: 0; left: 0;
  width: 3px; height: 100%;
}
.stat-card.earth::before { background: var(--earth); }
.stat-card.mars::before  { background: var(--mars); }
.stat-card.moon::before  { background: var(--moon); }
.stat-head {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 4px;
}
.stat-head h3 {
  margin: 0;
  font-size: 13px;
  font-weight: 600;
  letter-spacing: 0.005em;
}
.stat-head .orb {
  width: 8px; height: 8px;
  border-radius: 50%;
}
.stat-card.earth .stat-head .orb { background: var(--earth); }
.stat-card.mars  .stat-head .orb { background: var(--mars); }
.stat-card.moon  .stat-head .orb { background: var(--moon); }
.stat-const {
  font-size: 10px;
  color: var(--dim);
  letter-spacing: 0.02em;
  margin-bottom: 12px;
  font-family: "JetBrains Mono", monospace;
  text-transform: uppercase;
}
dl {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 7px 14px;
  margin: 0;
  font-size: 12px;
}
dt {
  color: var(--muted);
  font-weight: 400;
}
dd {
  margin: 0;
  font-variant-numeric: tabular-nums;
  font-weight: 500;
  color: var(--text);
  font-family: "JetBrains Mono", monospace;
  font-size: 12px;
}
.stat-card.earth dd[id$="range"],
.stat-card.earth dd[id$="peak"]  { color: var(--earth); }
.stat-card.mars  dd[id$="range"],
.stat-card.mars  dd[id$="peak"]  { color: var(--mars); }
.stat-card.moon  dd[id$="range"],
.stat-card.moon  dd[id$="peak"]  { color: var(--moon); }

/* ---------- Energy panel ---------- */
.energy-panel {
  background: var(--panel);
  border: 1px solid var(--border-mid);
  border-radius: 10px;
  padding: 14px 18px 10px;
  box-shadow: var(--shadow-sm);
}
.panel-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 10px;
}
.energy-legend {
  display: flex;
  gap: 14px;
  font-size: 11px;
  color: var(--muted);
  font-weight: 500;
  font-family: "JetBrains Mono", monospace;
}
.energy-legend i {
  display: inline-block;
  width: 14px; height: 2px;
  vertical-align: middle;
  margin-right: 6px;
}
.energy-legend .ke  { background: var(--text); }
.energy-legend .pe  { background: var(--muted); }
.energy-legend .tot { background: var(--accent); height: 1px; border-top: 1px dashed var(--accent); }
#energy { background: rgba(0, 0, 0, 0.2); }

/* ---------- Help text ---------- */
.help-text {
  font-size: 12px;
  line-height: 1.55;
  color: var(--muted);
  margin-bottom: 18px;
  padding: 10px 12px;
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: 6px;
  border-left: 2px solid var(--accent);
}

/* Toggle-style check */
.check.toggle {
  justify-content: flex-start;
}
.check.toggle .info {
  margin-left: auto;
}

/* ---------- Sound facts ---------- */
.sound-facts {
  margin-top: 14px;
  padding: 12px;
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 11.5px;
  color: var(--muted);
  line-height: 1.8;
  font-variant-numeric: tabular-nums;
  font-family: "JetBrains Mono", monospace;
  display: flex;
  flex-direction: column;
  gap: 2px;
}
.sound-facts b {
  color: var(--text);
  font-weight: 600;
}
.sf-name {
  display: inline-block;
  min-width: 42px;
  font-weight: 600;
  font-family: "Inter", sans-serif;
  font-size: 11px;
}
.sf-name.earth { color: var(--earth); }
.sf-name.mars  { color: var(--mars); }
.sf-name.moon  { color: var(--moon); }
.sf-note { color: var(--dim); font-size: 10.5px; }

/* ---------- Speed presets ---------- */
.speed-presets {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 6px;
  margin-top: 6px;
}
.preset {
  flex: none;
  background: var(--bg-elev);
  color: var(--muted);
  border: 1px solid var(--border-mid);
  border-radius: 5px;
  padding: 6px 8px;
  font-size: 11px;
  font-weight: 500;
  cursor: pointer;
  font-family: inherit;
  letter-spacing: 0.01em;
  transition: color 0.12s, border-color 0.12s, background 0.12s;
  box-shadow: none;
  white-space: nowrap;
}
.preset:hover {
  color: var(--text);
  background: var(--panel-2);
  border-color: var(--border-strong);
  filter: none;
}
.preset.active {
  color: var(--accent);
  border-color: var(--accent);
  background: var(--accent-dim);
}

/* ---------- Orbit facts ---------- */
.orbit-facts {
  margin-top: 14px;
  padding: 12px;
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 11.5px;
  color: var(--muted);
  line-height: 1.8;
  font-variant-numeric: tabular-nums;
  font-family: "JetBrains Mono", monospace;
}
.orbit-facts b {
  color: var(--text);
  font-weight: 600;
}
.orbit-facts .status {
  display: inline-block;
  padding: 2px 7px;
  border-radius: 4px;
  font-weight: 600;
  letter-spacing: 0.03em;
  text-transform: uppercase;
  font-size: 9.5px;
  font-family: "Inter", sans-serif;
}
.orbit-facts .status.orbiting {
  background: var(--accent-dim);
  color: var(--accent);
}
.orbit-facts .status.crashed {
  background: rgba(248, 113, 113, 0.12);
  color: var(--mars);
}
.orbit-facts .status.escaped {
  background: rgba(167, 139, 250, 0.12);
  color: #a78bfa;
}

/* ---------- Explainer ---------- */
.explainer {
  background: var(--panel);
  border: 1px solid var(--border-mid);
  border-radius: 10px;
  padding: 20px 24px;
  color: var(--muted);
  font-size: 13px;
  line-height: 1.65;
  box-shadow: var(--shadow-sm);
}
.explainer h2 {
  margin: 0 0 10px;
  color: var(--text);
  font-size: 14px;
  font-weight: 600;
  letter-spacing: 0.005em;
}
.explainer em {
  color: var(--text);
  font-style: normal;
  font-weight: 500;
}
pre {
  background: var(--bg-elev);
  padding: 12px 14px;
  border-radius: 6px;
  overflow-x: auto;
  color: var(--text);
  font-size: 12px;
  border: 1px solid var(--border);
  font-family: "JetBrains Mono", monospace;
  line-height: 1.6;
}

/* ---------- Responsive ---------- */

/* Tablet and small laptops */
@media (max-width: 980px) {
  header { padding: 20px 20px; }
  .tabs { padding: 0 20px; }
  main.mode {
    display: flex;
    flex-direction: column;
    padding: 20px;
    gap: 16px;
  }
  .canvas-wrap { order: 1; }
  .stats { order: 2; grid-template-columns: repeat(3, 1fr); }
  .controls { order: 3; position: static; padding: 20px; }
  .energy-panel { order: 4; }
  .explainer { order: 5; }
  .info::after {
    left: 0;
    width: calc(100vw - 80px);
    max-width: 300px;
  }
}

/* Phones */
@media (max-width: 700px) {
  header {
    padding: 16px 14px;
    flex-direction: column;
    align-items: flex-start;
    gap: 10px;
  }
  .title-block h1 { font-size: 19px; }
  .subtitle { font-size: 12.5px; }
  .planet-chips { gap: 6px; flex-wrap: wrap; }
  .chip { padding: 4px 9px; font-size: 11px; }

  /* Horizontally scrollable tabs */
  .tabs {
    padding: 0 12px;
    overflow-x: auto;
    overflow-y: hidden;
    flex-wrap: nowrap;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: none;
  }
  .tabs::-webkit-scrollbar { display: none; }
  .tab {
    flex-shrink: 0;
    padding: 12px 14px 11px;
    font-size: 12.5px;
    margin-right: 2px;
  }

  /* Main layout + panel chrome */
  main.mode { padding: 14px; gap: 14px; }
  .controls { padding: 16px; border-radius: 10px; }
  .canvas-wrap { padding: 10px; border-radius: 10px; }
  .stats { grid-template-columns: 1fr; gap: 10px; }
  .stat-card { padding: 14px 16px; }
  .explainer { padding: 16px 18px; font-size: 12.5px; }
  .energy-panel { padding: 12px 14px 8px; }

  /* Canvas heights — keep them usable on narrow screens */
  #sky          { height: 360px; }
  #energy       { height: 170px; }
  #collide-canvas { height: 400px; }
  #orbit-canvas { height: 460px; }
  #acoustic-canvas { height: 540px; }
  #pendulum-canvas { height: 460px; }
  #thermo-canvas   { height: 460px; }

  /* Legend line wraps cleanly */
  .legend { font-size: 11px; gap: 10px; }

  /* Larger tap targets */
  button { padding: 12px 14px; min-height: 44px; }
  .preset { padding: 9px 10px; font-size: 11.5px; min-height: 36px; }
  .check { padding: 10px 12px; min-height: 40px; }

  /* Slider thumb slightly bigger to tap */
  input[type="range"]::-webkit-slider-thumb { width: 18px; height: 18px; }
  input[type="range"]::-moz-range-thumb { width: 18px; height: 18px; }

  /* Tooltip: pinned to viewport bottom so it can't be clipped */
  .info::after {
    position: fixed;
    left: 12px;
    right: 12px;
    top: auto;
    bottom: 20px;
    width: auto;
    max-width: none;
    transform: translateY(8px);
    z-index: 1000;
  }
  .info:hover::after, .info:focus::after {
    transform: translateY(0);
  }

  /* Inspector hidden on phones (no hover on touch) */
  .inspector { display: none; }

  /* Speed presets: 2x2 still */
  .speed-presets { gap: 5px; }

  /* Tighter help text */
  .help-text { font-size: 11.5px; padding: 9px 11px; }
  .sound-facts, .orbit-facts { font-size: 11px; line-height: 1.7; }
}