:root {
  --bg-1: #0b1220;
  --bg-2: #111b2d;
  --bg-3: #0b1220;
  --ink: #e2e8f0;
  --muted: #94a3b8;
  --accent: #7dd3fc;
  --accent-strong: #38bdf8;
  --panel: rgba(11, 18, 32, 0.85);
  --panel-soft: rgba(15, 23, 42, 0.7);
  --panel-border: rgba(125, 211, 252, 0.18);
  --shadow: rgba(2, 6, 23, 0.6);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  overflow: hidden;
  color: var(--ink);
  font-family: "Segoe UI", Arial, sans-serif;
  background:
    radial-gradient(760px 480px at 16% 10%, rgba(125, 211, 252, 0.18), transparent 60%),
    radial-gradient(700px 440px at 85% 0%, rgba(45, 212, 191, 0.12), transparent 55%),
    linear-gradient(135deg, var(--bg-1), var(--bg-2) 55%, var(--bg-3));
}

#nbody-canvas {
  position: fixed;
  inset: 0;
  width: 100vw;
  height: 100vh;
  display: block;
  z-index: 0;
  animation: fade-in 1s ease;
}

.home-link {
  position: fixed;
  top: 24px;
  right: 24px;
  z-index: 2;
  border: 1px solid var(--panel-border);
  background: var(--panel-soft);
  color: var(--muted);
  border-radius: 999px;
  padding: 6px 12px;
  text-decoration: none;
  font-size: 0.85rem;
  backdrop-filter: blur(6px);
  box-shadow: 0 8px 24px var(--shadow);
  transition: transform 0.2s ease, border-color 0.2s ease, color 0.2s ease;
}

.home-link:hover {
  transform: translateY(-1px);
  border-color: var(--accent);
  color: var(--accent);
}

#hud {
  position: fixed;
  top: 24px;
  left: 24px;
  z-index: 2;
  display: flex;
  flex-direction: column;
  gap: 12px;
  padding: 16px 18px;
  min-width: 220px;
  background: linear-gradient(135deg, rgba(11, 18, 32, 0.92), rgba(11, 18, 32, 0.7));
  border: 1px solid var(--panel-border);
  border-radius: 16px;
  backdrop-filter: blur(10px);
  box-shadow: 0 18px 40px var(--shadow);
  animation: float-up 0.8s ease;
}

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

#hud .title {
  text-transform: uppercase;
  letter-spacing: 0.12em;
  font-size: 12px;
  font-weight: 600;
  color: var(--accent);
}

.hud-body {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

#hud .row {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 13px;
  color: var(--muted);
}

#hud .row .label {
  flex: 0 0 92px;
  color: var(--muted);
}

#hud .row .value {
  margin-left: auto;
  font-variant-numeric: tabular-nums;
  color: var(--ink);
}

#hud .row input[type="number"] {
  width: 70px;
}

#hud .row input[type="range"] {
  flex: 1;
}

#hud .row.checkbox {
  gap: 6px;
}

#hud button {
  border: 1px solid var(--panel-border);
  background: var(--panel-soft);
  color: var(--muted);
  padding: 6px 12px;
  border-radius: 999px;
  cursor: pointer;
  font-size: 12px;
  letter-spacing: 0.02em;
  transition: transform 0.2s ease, border-color 0.2s ease, color 0.2s ease;
}

#hud button:hover {
  transform: translateY(-1px) scale(1.02);
  border-color: var(--accent);
  color: var(--accent);
}

#hud .hud-toggle {
  border: 1px solid var(--panel-border);
  background: rgba(15, 23, 42, 0.8);
  color: var(--muted);
  border-radius: 999px;
  padding: 4px 10px;
  cursor: pointer;
  font-size: 11px;
  letter-spacing: 0.03em;
  text-transform: uppercase;
  transition: transform 0.2s ease, border-color 0.2s ease, color 0.2s ease;
}

#hud .hud-toggle:hover {
  transform: translateY(-1px);
  border-color: var(--accent-strong);
  color: var(--accent-strong);
}

#hud input {
  font-family: inherit;
  color: var(--ink);
  background: rgba(15, 23, 42, 0.6);
  border: 1px solid var(--panel-border);
  border-radius: 8px;
  padding: 4px 6px;
  accent-color: var(--accent);
}

#hud input:focus {
  outline: 1px solid rgba(125, 211, 252, 0.5);
}

.stats {
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  font-size: 11px;
  color: var(--ink);
  background: rgba(15, 23, 42, 0.7);
  padding: 8px;
  border-radius: 10px;
  line-height: 1.4;
  white-space: pre-line;
}

#hud.collapsed {
  padding: 12px 14px;
  min-width: 180px;
}

#hud.collapsed .hud-body {
  display: none;
}

@media (max-width: 720px) {
  #hud {
    top: auto;
    bottom: 16px;
    left: 16px;
    right: 16px;
    min-width: auto;
  }

  #hud .row {
    flex-wrap: wrap;
  }
}

@keyframes fade-in {
  from {
    opacity: 0;
  }
  to {
    opacity: 1;
  }
}

@keyframes float-up {
  from {
    opacity: 0;
    transform: translateY(12px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}