/* ========================================================================
   Design Tokens
   ======================================================================== */
:root {
  /* Background */
  --bg-deep: #080a14;
  --surface: rgba(16, 20, 35, 0.85);
  --surface-alt: rgba(22, 27, 45, 0.9);
  --border: rgba(255, 255, 255, 0.06);
  --border-lite: rgba(255, 255, 255, 0.1);

  /* Accent */
  --accent: #6e8efb;
  --accent-subtle: rgba(110, 142, 251, 0.12);

  /* Body colors */
  --color-planet: #6e8efb;
  --color-star: #f0c060;
  --color-moon: #94a0b8;

  /* Text */
  --text-1: rgba(255, 255, 255, 0.92);
  --text-2: rgba(255, 255, 255, 0.55);
  --text-3: rgba(255, 255, 255, 0.3);

  /* Typography */
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, system-ui, sans-serif;
  --font-mono: 'JetBrains Mono', 'SF Mono', 'Consolas', monospace;

  /* Spacing */
  --sp-1: 4px;
  --sp-2: 8px;
  --sp-3: 12px;
  --sp-4: 16px;
  --sp-5: 24px;

  /* Radius */
  --r-sm: 6px;
  --r-md: 8px;
  --r-pill: 100px;

  /* Motion */
  --ease: cubic-bezier(0.25, 0.46, 0.45, 0.94);
  --dur: 180ms;
}

/* ========================================================================
   Reset
   ======================================================================== */
*,
*::before,
*::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html,
body {
  width: 100%;
  height: 100%;
  overflow: hidden;
  font-family: var(--font-sans);
  background: var(--bg-deep);
  color: var(--text-1);
  cursor: crosshair;
  -webkit-font-smoothing: antialiased;
}

/* ========================================================================
   Canvas
   ======================================================================== */
#sim-canvas {
  display: block;
  width: 100%;
  height: 100%;
  position: fixed;
  inset: 0;
  z-index: 0;
}

/* ========================================================================
   Top Bar
   ======================================================================== */
#top-bar {
  position: fixed;
  top: var(--sp-3);
  left: 50%;
  transform: translateX(-50%);
  z-index: 10;
  display: flex;
  align-items: center;
  gap: var(--sp-4);
  padding: 6px var(--sp-3);
  background: var(--surface);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border: 1px solid var(--border);
  border-radius: var(--r-md);
  animation: enter-y 0.4s var(--ease) both;
}

@keyframes enter-y {
  from {
    opacity: 0;
    transform: translateX(-50%) translateY(-12px);
  }

  to {
    opacity: 1;
    transform: translateX(-50%) translateY(0);
  }
}

/* Logo */
.logo {
  display: flex;
  align-items: center;
  gap: var(--sp-2);
  white-space: nowrap;
  padding-right: var(--sp-2);
  border-right: 1px solid var(--border-lite);
}

.logo-icon {
  font-size: 1.1rem;
  color: var(--accent);
  opacity: 0.8;
}

.logo h1 {
  font-size: 0.82rem;
  font-weight: 600;
  letter-spacing: -0.01em;
  color: var(--text-1);
}

/* ========================================================================
   Body Picker
   ======================================================================== */
#body-picker {
  display: flex;
  gap: 2px;
}

.body-btn {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 5px 12px;
  border: 1px solid transparent;
  border-radius: var(--r-sm);
  background: transparent;
  color: var(--text-2);
  font-family: var(--font-sans);
  font-size: 0.78rem;
  font-weight: 500;
  cursor: pointer;
  transition: all var(--dur) var(--ease);
  white-space: nowrap;
}

.body-btn:hover {
  color: var(--text-1);
  background: var(--accent-subtle);
}

.body-btn.active {
  color: var(--text-1);
  background: var(--accent-subtle);
  border-color: rgba(110, 142, 251, 0.2);
}

.body-preview {
  display: inline-block;
  width: 8px;
  height: 8px;
  border-radius: 50%;
}

.planet-preview {
  background: var(--color-planet);
}

.star-preview {
  background: var(--color-star);
}

.moon-preview {
  background: var(--color-moon);
}

/* ========================================================================
   Action Buttons
   ======================================================================== */
.top-actions {
  display: flex;
  gap: 2px;
  padding-left: var(--sp-2);
  border-left: 1px solid var(--border-lite);
}

.action-btn {
  display: flex;
  align-items: center;
  gap: 5px;
  padding: 5px 12px;
  border: 1px solid transparent;
  border-radius: var(--r-sm);
  background: transparent;
  color: var(--text-2);
  font-family: var(--font-sans);
  font-size: 0.78rem;
  font-weight: 500;
  cursor: pointer;
  transition: all var(--dur) var(--ease);
  white-space: nowrap;
}

.action-btn:hover {
  color: var(--text-1);
  background: var(--accent-subtle);
}

.action-icon {
  font-size: 0.68rem;
}

/* ========================================================================
   Hint
   ======================================================================== */
#hint-overlay {
  position: fixed;
  bottom: 72px;
  left: 50%;
  transform: translateX(-50%);
  z-index: 10;
  padding: var(--sp-2) var(--sp-4);
  background: var(--surface);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid var(--border);
  border-radius: var(--r-pill);
  pointer-events: none;
  animation: fade-in 0.5s 0.4s var(--ease) both;
  transition: opacity 0.8s var(--ease);
}

#hint-overlay.hidden {
  opacity: 0;
}

#hint-overlay p {
  font-size: 0.72rem;
  color: var(--text-2);
  white-space: nowrap;
}

#hint-overlay strong {
  color: var(--text-1);
  font-weight: 600;
}

@keyframes fade-in {
  from {
    opacity: 0;
    transform: translateX(-50%) translateY(8px);
  }

  to {
    opacity: 1;
    transform: translateX(-50%) translateY(0);
  }
}

/* ========================================================================
   Info Panel
   ======================================================================== */
#info-panel {
  position: fixed;
  bottom: var(--sp-3);
  left: var(--sp-3);
  z-index: 10;
  display: flex;
  flex-direction: column;
  gap: var(--sp-1);
  padding: var(--sp-3);
  background: var(--surface);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border: 1px solid var(--border);
  border-radius: var(--r-md);
  min-width: 110px;
  animation: slide-up 0.4s 0.1s var(--ease) both;
}

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

  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.info-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: var(--sp-5);
}

.info-label {
  font-size: 0.68rem;
  font-weight: 500;
  color: var(--text-3);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.info-value {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  font-weight: 400;
  color: var(--text-2);
}

/* ========================================================================
   Controls Panel
   ======================================================================== */
#controls-panel {
  position: fixed;
  bottom: var(--sp-3);
  right: var(--sp-3);
  z-index: 10;
  display: flex;
  flex-direction: column;
  gap: var(--sp-3);
  padding: var(--sp-3) var(--sp-4);
  background: var(--surface);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border: 1px solid var(--border);
  border-radius: var(--r-md);
  min-width: 170px;
  animation: slide-up 0.4s 0.2s var(--ease) both;
}

.control-group {
  display: flex;
  flex-direction: column;
  gap: 3px;
}

.control-group label {
  font-size: 0.68rem;
  font-weight: 500;
  color: var(--text-3);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

/* ========================================================================
   Range Slider
   ======================================================================== */
input[type="range"] {
  -webkit-appearance: none;
  appearance: none;
  width: 100%;
  height: 3px;
  border-radius: 2px;
  background: rgba(255, 255, 255, 0.08);
  outline: none;
  cursor: pointer;
}

input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: var(--accent);
  border: none;
  cursor: pointer;
  transition: transform var(--dur) var(--ease);
}

input[type="range"]::-webkit-slider-thumb:hover {
  transform: scale(1.3);
}

input[type="range"]::-moz-range-thumb {
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: var(--accent);
  border: none;
  cursor: pointer;
}

/* ========================================================================
   Responsive
   ======================================================================== */
@media (max-width: 768px) {
  #top-bar {
    flex-wrap: wrap;
    justify-content: center;
    gap: var(--sp-2);
    padding: var(--sp-2);
    max-width: calc(100% - var(--sp-5));
  }

  .logo {
    border-right: none;
    padding-right: 0;
  }

  .top-actions {
    border-left: none;
    padding-left: 0;
  }
}