/* ===== Design tokens ===== */
:root {
  --bg-0: #04060d;
  --bg-1: #0a0f1f;
  --glass: rgba(18, 24, 44, 0.55);
  --glass-strong: rgba(22, 29, 54, 0.72);
  --border: rgba(148, 163, 255, 0.12);
  --border-strong: rgba(148, 163, 255, 0.25);
  --text: #e6e9f5;
  --text-dim: #8b93b0;
  --text-faint: #5b6382;
  --accent-a: #7c5cff;
  --accent-b: #22d3ee;
  --accent-grad: linear-gradient(135deg, var(--accent-a), var(--accent-b));
  --cold: #38bdf8;
  --hot: #fb7185;
  --amber: #fbbf24;
  --teal: #2dd4bf;
  --radius-lg: 18px;
  --radius-md: 12px;
  --radius-sm: 8px;
  --font-ui: 'Inter', system-ui, sans-serif;
  --font-display: 'Outfit', 'Inter', sans-serif;
  --font-mono: 'JetBrains Mono', ui-monospace, monospace;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  height: 100%;
  background: var(--bg-0);
  color: var(--text);
  font-family: var(--font-ui);
  font-size: 14px;
  -webkit-font-smoothing: antialiased;
  overflow: hidden;
}

/* ===== Layout ===== */
.app {
  display: grid;
  grid-template-columns: 1fr 360px;
  height: 100vh;
  gap: 16px;
  padding: 16px;
  background:
    radial-gradient(1200px 800px at 30% 40%, rgba(124, 92, 255, 0.10), transparent 60%),
    radial-gradient(900px 700px at 80% 90%, rgba(34, 211, 238, 0.07), transparent 60%),
    linear-gradient(180deg, var(--bg-1), var(--bg-0));
}

.stage {
  position: relative;
  border-radius: var(--radius-lg);
  overflow: hidden;
  border: 1px solid var(--border);
  background:
    radial-gradient(circle at 50% 50%, rgba(40, 52, 100, 0.35), transparent 70%),
    #060913;
  min-height: 0;
}

#sim-canvas {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  display: block;
}

.glass {
  background: var(--glass);
  border: 1px solid var(--border);
  backdrop-filter: blur(18px) saturate(140%);
  -webkit-backdrop-filter: blur(18px) saturate(140%);
  box-shadow: 0 10px 40px rgba(0, 0, 0, 0.35), inset 0 1px 0 rgba(255, 255, 255, 0.04);
}

/* ===== HUD ===== */
.hud {
  position: absolute;
  border-radius: var(--radius-md);
  padding: 12px 14px;
  pointer-events: none;
}

.hud-top {
  top: 16px;
  left: 16px;
  display: flex;
  align-items: center;
  gap: 18px;
}

.hud-metrics { display: flex; gap: 16px; }
.hud-metric { display: flex; flex-direction: column; gap: 2px; }
.hud-metric .k {
  font-size: 10px; text-transform: uppercase; letter-spacing: 0.08em; color: var(--text-faint);
}
.hud-metric .v { font-family: var(--font-mono); font-size: 15px; }

.phase-badge {
  --pc: var(--cold);
  display: flex;
  align-items: center;
  gap: 10px;
  font-family: var(--font-display);
  font-weight: 600;
  font-size: 20px;
  padding: 6px 14px 6px 10px;
  border-radius: 999px;
  background: color-mix(in srgb, var(--pc) 14%, transparent);
  border: 1px solid color-mix(in srgb, var(--pc) 40%, transparent);
  color: color-mix(in srgb, var(--pc) 70%, white);
  transition: background 0.5s, border-color 0.5s, color 0.5s;
  min-width: 150px;
}
.phase-dot {
  width: 10px; height: 10px; border-radius: 50%;
  background: var(--pc);
  box-shadow: 0 0 12px var(--pc);
  animation: pulse 1.8s ease-in-out infinite;
}
.phase-badge[data-phase='gas'] { --pc: #fb923c; }
.phase-badge[data-phase='mixed-liquid'] { --pc: #a78bfa; }
.phase-badge[data-phase='liquid'] { --pc: #38bdf8; }
.phase-badge[data-phase='mixed-solid'] { --pc: #67e8f9; }
.phase-badge[data-phase='solid'] { --pc: #e0f2fe; }

@keyframes pulse {
  0%, 100% { transform: scale(1); opacity: 1; }
  50% { transform: scale(0.7); opacity: 0.6; }
}

.gravity-indicator {
  position: absolute;
  top: 20px;
  right: 20px;
  display: flex;
  align-items: center;
  gap: 6px;
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--amber);
  padding: 6px 10px;
  border-radius: 999px;
  background: rgba(251, 191, 36, 0.08);
  border: 1px solid rgba(251, 191, 36, 0.25);
  opacity: 0;
  transform: translateY(-6px);
  transition: opacity 0.3s, transform 0.3s;
}
.gravity-indicator.on { opacity: 1; transform: none; }
.gravity-indicator svg { animation: drop 1.4s ease-in-out infinite; }
@keyframes drop {
  0%, 100% { transform: translateY(-2px); }
  50% { transform: translateY(2px); }
}

.hud-bottom {
  left: 16px;
  bottom: 16px;
  width: min(360px, calc(100% - 32px));
  padding: 10px 12px 8px;
}
.chart-head {
  display: flex; justify-content: space-between; align-items: center;
  font-size: 11px; color: var(--text-dim); margin-bottom: 6px;
}
.chart-title { text-transform: uppercase; letter-spacing: 0.08em; font-weight: 600; }
.legend { display: flex; gap: 10px; }
.lg { display: inline-flex; align-items: center; gap: 5px; }
.lg::before { content: ''; width: 12px; height: 2px; border-radius: 2px; background: currentColor; }
.lg-temp { color: var(--amber); }
.lg-out { color: var(--hot); }
.lg-cond { color: var(--teal); }
.lg.hidden { display: none; }
#chart-canvas { width: 100%; height: 96px; display: block; }

/* ===== Cluster panel ===== */
.hud-clusters {
  right: 16px;
  bottom: 16px;
  width: min(400px, calc(100% - 32px));
  padding: 10px 12px 10px;
  pointer-events: auto;
}
.cl-title {
  display: inline-flex; align-items: center; gap: 6px;
  background: none; border: 0; padding: 0; cursor: pointer;
  font: 600 11px var(--font-ui); letter-spacing: 0.08em; text-transform: uppercase;
  color: var(--text-dim);
}
.cl-title:hover { color: var(--text); }
.cl-title .chev { transition: transform 0.2s; }
.hud-clusters.collapsed .chev { transform: rotate(-90deg); }
.hud-clusters.collapsed .cl-body { display: none; }
.hud-clusters.collapsed .chart-head { margin-bottom: 0; }
.cl-actions { display: flex; align-items: center; gap: 6px; }
.segmented-mini { padding: 2px; gap: 2px; border-radius: 7px; }
.segmented-mini .seg { padding: 3px 8px; font-size: 10.5px; border-radius: 5px; }
#cl-hist { width: 100%; height: 104px; display: block; }
#cl-heat { width: 100%; height: 132px; display: block; margin-top: 6px; }
.cl-stats {
  display: grid; grid-template-columns: repeat(4, 1fr); gap: 6px; margin-top: 8px;
}
.cl-stats > div { display: flex; flex-direction: column; gap: 2px; }
.cl-stats .k { font-size: 9.5px; color: var(--text-faint); text-transform: uppercase; letter-spacing: 0.06em; }
.cl-stats .v { font-family: var(--font-mono); font-size: 12px; }

@media (max-width: 1250px) {
  .hud-bottom { width: min(300px, calc(50% - 24px)); }
  .hud-clusters { width: min(360px, calc(50% - 24px)); }
}

/* ===== Panel ===== */
.panel {
  border-radius: var(--radius-lg);
  padding: 20px 18px;
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  gap: 18px;
  scrollbar-width: thin;
  scrollbar-color: rgba(148, 163, 255, 0.2) transparent;
}

.panel-header h1 {
  margin: 0 0 6px;
  font-family: var(--font-display);
  font-size: 24px;
  font-weight: 700;
  letter-spacing: -0.01em;
  background: var(--accent-grad);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.panel-header p { margin: 0; color: var(--text-dim); line-height: 1.5; font-size: 13px; }

.group { display: flex; flex-direction: column; gap: 12px; }
.group h2 {
  margin: 0;
  font-size: 11px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-faint);
  display: flex; align-items: center; gap: 8px;
}
.group h2::after { content: ''; flex: 1; height: 1px; background: var(--border); }

.control { display: flex; flex-direction: column; gap: 8px; }
.control[hidden] { display: none; }
.control label {
  display: flex; justify-content: space-between; align-items: baseline;
  font-size: 13px; color: var(--text);
}
.control output {
  font-family: var(--font-mono); font-size: 12px; color: var(--accent-b);
  background: rgba(34, 211, 238, 0.08); padding: 2px 8px; border-radius: 6px;
}
.scale { display: flex; justify-content: space-between; font-size: 10px; color: var(--text-faint); }
.inline { display: flex; gap: 10px; align-items: center; }
.inline .range { flex: 1; }
.hint { margin: 0; font-size: 12px; color: var(--text-dim); line-height: 1.5; }

/* ===== Range inputs ===== */
.range {
  --p: 50%;
  -webkit-appearance: none;
  appearance: none;
  width: 100%;
  height: 22px;
  background: transparent;
  cursor: pointer;
  margin: 0;
}
.range::-webkit-slider-runnable-track {
  height: 6px; border-radius: 6px;
  background: linear-gradient(90deg, var(--accent-a), var(--accent-b)) 0 / var(--p) 100% no-repeat, rgba(148, 163, 255, 0.12);
}
.range::-moz-range-track {
  height: 6px; border-radius: 6px;
  background: linear-gradient(90deg, var(--accent-a), var(--accent-b)) 0 / var(--p) 100% no-repeat, rgba(148, 163, 255, 0.12);
}
.range-thermo::-webkit-slider-runnable-track {
  background: linear-gradient(90deg, #2563eb, #38bdf8 35%, #94a3b8 50%, #fb923c 65%, #f43f5e);
}
.range-thermo::-moz-range-track {
  background: linear-gradient(90deg, #2563eb, #38bdf8 35%, #94a3b8 50%, #fb923c 65%, #f43f5e);
}
.range::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 18px; height: 18px; margin-top: -6px;
  border-radius: 50%;
  background: #fff;
  border: 3px solid var(--bg-1);
  box-shadow: 0 0 0 2px var(--accent-b), 0 4px 12px rgba(0, 0, 0, 0.4);
  transition: transform 0.15s, box-shadow 0.15s;
}
.range::-moz-range-thumb {
  width: 14px; height: 14px; border-radius: 50%; background: #fff;
  border: 3px solid var(--bg-1);
  box-shadow: 0 0 0 2px var(--accent-b), 0 4px 12px rgba(0, 0, 0, 0.4);
}
.range:hover::-webkit-slider-thumb { transform: scale(1.15); box-shadow: 0 0 0 2px var(--accent-b), 0 0 16px rgba(34, 211, 238, 0.6); }
.range:focus-visible { outline: none; }
.range:focus-visible::-webkit-slider-thumb { box-shadow: 0 0 0 3px var(--accent-a), 0 0 18px rgba(124, 92, 255, 0.7); }

/* ===== Buttons ===== */
.row-buttons { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; }
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  padding: 10px 14px;
  font: 600 13px var(--font-ui);
  color: var(--text);
  background: rgba(148, 163, 255, 0.06);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: background 0.2s, transform 0.1s, border-color 0.2s, box-shadow 0.2s;
}
.btn:hover { background: rgba(148, 163, 255, 0.12); border-color: rgba(148, 163, 255, 0.4); }
.btn:active { transform: translateY(1px) scale(0.98); }
.btn-primary {
  background: var(--accent-grad);
  border-color: transparent;
  color: #fff;
  box-shadow: 0 6px 20px rgba(124, 92, 255, 0.35);
}
.btn-primary:hover { background: var(--accent-grad); box-shadow: 0 8px 28px rgba(34, 211, 238, 0.4); }
.btn-small { padding: 5px 10px; font-size: 11px; }
.btn-small.active { border-color: var(--accent-b); color: var(--accent-b); }

.segmented {
  display: grid; grid-template-columns: 1fr 1fr;
  padding: 3px; gap: 3px;
  background: rgba(0, 0, 0, 0.25);
  border: 1px solid var(--border);
  border-radius: 10px;
}
.seg {
  padding: 8px 6px;
  font: 500 12px var(--font-ui);
  color: var(--text-dim);
  background: transparent;
  border: 0; border-radius: 7px;
  cursor: pointer;
  transition: color 0.2s, background 0.2s, box-shadow 0.2s;
}
.seg:hover { color: var(--text); }
.seg.active {
  color: #fff;
  background: linear-gradient(135deg, rgba(124, 92, 255, 0.55), rgba(34, 211, 238, 0.45));
  box-shadow: 0 2px 10px rgba(124, 92, 255, 0.3);
}

/* ===== Toggle ===== */
.toggle { display: flex; align-items: center; gap: 10px; cursor: pointer; font-size: 13px; }
.toggle input { position: absolute; opacity: 0; pointer-events: none; }
.toggle-track {
  width: 36px; height: 20px; border-radius: 999px;
  background: rgba(148, 163, 255, 0.15);
  position: relative; transition: background 0.2s;
}
.toggle-thumb {
  position: absolute; top: 3px; left: 3px;
  width: 14px; height: 14px; border-radius: 50%; background: #fff;
  transition: transform 0.2s;
}
.toggle input:checked + .toggle-track { background: var(--accent-grad); }
.toggle input:checked + .toggle-track .toggle-thumb { transform: translateX(16px); }
.toggle input:focus-visible + .toggle-track { box-shadow: 0 0 0 2px var(--accent-b); }

/* ===== Stats ===== */
.stats { display: grid; grid-template-columns: 1fr 1fr 1fr; gap: 8px; }
.stat {
  display: flex; flex-direction: column; gap: 4px;
  padding: 8px 10px;
  background: rgba(0, 0, 0, 0.22);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
}
.stat .k { font-size: 10px; color: var(--text-faint); text-transform: uppercase; letter-spacing: 0.06em; }
.stat .v { font-family: var(--font-mono); font-size: 13px; }

.panel-footer {
  margin-top: auto;
  font-size: 11px; color: var(--text-faint); line-height: 1.6;
}
kbd {
  font-family: var(--font-mono); font-size: 10px;
  padding: 1px 5px; border-radius: 4px;
  border: 1px solid var(--border-strong); background: rgba(255, 255, 255, 0.04);
  color: var(--text-dim);
}

/* ===== Responsive ===== */
@media (max-width: 900px) {
  html, body { overflow: auto; }
  .app { grid-template-columns: 1fr; height: auto; }
  .stage { height: 70vh; }
  .hud-metric:nth-child(3) { display: none; }
}