:root {
  --bg-primary: #0a0c16;
  --panel-bg: rgba(14, 18, 33, 0.78);
  --panel-border: rgba(255, 255, 255, 0.12);
  --accent-cyan: #00f0ff;
  --accent-magenta: #ff007b;
  --accent-purple: #8b5cf6;
  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;
  --glass-shadow: 0 8px 32px 0 rgba(0, 0, 0, 0.45);
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Courier New', monospace;
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  -webkit-tap-highlight-color: transparent;
}

body, html {
  width: 100%;
  height: 100%;
  overflow: hidden;
  background-color: var(--bg-primary);
  font-family: var(--font-sans);
  color: var(--text-primary);
  user-select: none;
}

#canvas-container {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: 1;
}

canvas {
  display: block;
  width: 100%;
  height: 100%;
}

/* Glassmorphism Panels */
.glass-panel {
  background: var(--panel-bg);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border: 1px solid var(--panel-border);
  box-shadow: var(--glass-shadow);
  border-radius: var(--radius-lg);
  pointer-events: auto;
}

/* Header Banner */
.header-bar {
  position: absolute;
  top: 16px;
  left: 16px;
  z-index: 10;
  padding: 12px 20px;
  display: flex;
  align-items: center;
  gap: 16px;
}

.logo-badge {
  display: flex;
  align-items: center;
  gap: 10px;
}

.logo-icon {
  width: 32px;
  height: 32px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-sm);
  background: linear-gradient(135deg, var(--accent-cyan), var(--accent-magenta));
  color: #fff;
  font-size: 1.1rem;
}

.title-group h1 {
  font-size: 1.05rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  background: linear-gradient(90deg, #fff, #a5b4fc);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.title-group p {
  font-size: 0.72rem;
  color: var(--text-secondary);
}

/* Stats HUD */
.stats-hud {
  position: absolute;
  top: 16px;
  right: 16px;
  z-index: 10;
  padding: 8px 16px;
  display: flex;
  gap: 16px;
  font-family: var(--font-mono);
  font-size: 0.75rem;
}

.stat-item {
  display: flex;
  flex-direction: column;
  align-items: flex-end;
}

.stat-label {
  font-size: 0.65rem;
  color: var(--text-muted);
  text-transform: uppercase;
}

.stat-value {
  color: var(--accent-cyan);
  font-weight: 600;
}

/* Mathematical Formula Card (Bottom Left) */
.formula-hud {
  position: absolute;
  bottom: 20px;
  left: 20px;
  z-index: 10;
  padding: 14px 18px;
  max-width: 440px;
}

.formula-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 6px;
}

.formula-title {
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-muted);
  font-weight: 600;
}

.formula-display {
  font-family: var(--font-mono);
  font-size: 0.95rem;
  color: var(--accent-cyan);
  background: rgba(0, 0, 0, 0.35);
  padding: 8px 12px;
  border-radius: var(--radius-sm);
  border-left: 3px solid var(--accent-cyan);
  word-break: break-all;
}

.formula-detail {
  margin-top: 6px;
  font-size: 0.7rem;
  color: var(--text-secondary);
  display: flex;
  justify-content: space-between;
}

/* Main Control Sidebar */
.controls-sidebar {
  position: absolute;
  top: 76px;
  right: 16px;
  bottom: 20px;
  width: 340px;
  z-index: 10;
  display: flex;
  flex-direction: column;
  overflow: hidden;
  transition: transform 0.3s cubic-bezier(0.16, 1, 0.3, 1), opacity 0.3s ease;
}

.controls-sidebar.collapsed {
  transform: translateX(360px);
  pointer-events: none;
}

.sidebar-header {
  padding: 14px 18px;
  border-bottom: 1px solid var(--panel-border);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.sidebar-header h2 {
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  font-weight: 700;
  color: #fff;
}

.sidebar-scroll {
  flex: 1;
  overflow-y: auto;
  padding: 16px;
  display: flex;
  flex-direction: column;
  gap: 18px;
}

/* Custom scrollbar */
.sidebar-scroll::-webkit-scrollbar {
  width: 5px;
}
.sidebar-scroll::-webkit-scrollbar-thumb {
  background: rgba(255, 255, 255, 0.15);
  border-radius: 4px;
}

.control-group {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.control-group-title {
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.07em;
  color: var(--accent-cyan);
  font-weight: 700;
  display: flex;
  align-items: center;
  gap: 6px;
}

/* Row & Label styling */
.control-row {
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.control-row-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.78rem;
  color: var(--text-secondary);
}

.slider-val {
  font-family: var(--font-mono);
  color: #fff;
  font-size: 0.75rem;
  background: rgba(255, 255, 255, 0.08);
  padding: 2px 6px;
  border-radius: 4px;
}

/* Sliders */
input[type="range"] {
  -webkit-appearance: none;
  appearance: none;
  width: 100%;
  height: 6px;
  background: rgba(255, 255, 255, 0.12);
  border-radius: 3px;
  outline: none;
  cursor: pointer;
  transition: background 0.2s;
}

input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: var(--accent-cyan);
  box-shadow: 0 0 10px var(--accent-cyan);
  cursor: pointer;
  transition: transform 0.15s, background 0.2s;
}

input[type="range"]::-webkit-slider-thumb:hover {
  transform: scale(1.2);
}

/* Segmented Buttons */
.segmented-control {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(60px, 1fr));
  gap: 4px;
  background: rgba(0, 0, 0, 0.3);
  padding: 3px;
  border-radius: var(--radius-sm);
  border: 1px solid rgba(255, 255, 255, 0.08);
}

.seg-btn {
  background: transparent;
  border: none;
  color: var(--text-secondary);
  font-size: 0.72rem;
  font-weight: 500;
  padding: 6px 8px;
  border-radius: 6px;
  cursor: pointer;
  transition: all 0.2s;
  text-align: center;
  white-space: nowrap;
}

.seg-btn:hover {
  color: #fff;
  background: rgba(255, 255, 255, 0.05);
}

.seg-btn.active {
  background: var(--accent-purple);
  color: #fff;
  font-weight: 600;
  box-shadow: 0 2px 8px rgba(139, 92, 246, 0.4);
}

/* Select dropdown */
select.custom-select {
  width: 100%;
  background: rgba(0, 0, 0, 0.35);
  border: 1px solid rgba(255, 255, 255, 0.15);
  color: #fff;
  padding: 7px 10px;
  border-radius: var(--radius-sm);
  font-size: 0.78rem;
  outline: none;
  cursor: pointer;
  font-family: inherit;
}

select.custom-select option {
  background: #0f172a;
  color: #fff;
}

/* Buttons Grid */
.button-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
}

.action-btn {
  background: rgba(255, 255, 255, 0.08);
  border: 1px solid rgba(255, 255, 255, 0.12);
  color: #fff;
  padding: 8px 12px;
  border-radius: var(--radius-sm);
  font-size: 0.76rem;
  font-weight: 500;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  transition: all 0.2s;
}

.action-btn:hover {
  background: rgba(255, 255, 255, 0.16);
  border-color: rgba(255, 255, 255, 0.25);
  transform: translateY(-1px);
}

.action-btn.active {
  background: var(--accent-cyan);
  color: #050b14;
  font-weight: 700;
  border-color: var(--accent-cyan);
  box-shadow: 0 0 12px rgba(0, 240, 255, 0.4);
}

/* Toggle Switch */
.toggle-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.78rem;
  color: var(--text-secondary);
}

.toggle-switch {
  position: relative;
  display: inline-block;
  width: 38px;
  height: 20px;
}

.toggle-switch input {
  opacity: 0;
  width: 0;
  height: 0;
}

.toggle-slider {
  position: absolute;
  cursor: pointer;
  top: 0; left: 0; right: 0; bottom: 0;
  background-color: rgba(255, 255, 255, 0.15);
  transition: .3s;
  border-radius: 20px;
}

.toggle-slider:before {
  position: absolute;
  content: "";
  height: 14px;
  width: 14px;
  left: 3px;
  bottom: 3px;
  background-color: white;
  transition: .3s;
  border-radius: 50%;
}

input:checked + .toggle-slider {
  background-color: var(--accent-cyan);
}

input:checked + .toggle-slider:before {
  transform: translateX(18px);
}

/* Preset Chips */
.presets-container {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.preset-chip {
  background: rgba(255, 255, 255, 0.06);
  border: 1px solid rgba(255, 255, 255, 0.12);
  color: var(--text-secondary);
  font-size: 0.72rem;
  padding: 4px 10px;
  border-radius: 20px;
  cursor: pointer;
  transition: all 0.2s;
}

.preset-chip:hover {
  background: rgba(0, 240, 255, 0.15);
  border-color: var(--accent-cyan);
  color: #fff;
}

/* Toggle Panel Button (Floating) */
.toggle-sidebar-btn {
  position: absolute;
  top: 16px;
  right: 16px;
  z-index: 12;
  width: 40px;
  height: 40px;
  border-radius: var(--radius-sm);
  background: var(--panel-bg);
  backdrop-filter: blur(12px);
  border: 1px solid var(--panel-border);
  color: #fff;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.1rem;
  transition: all 0.2s;
}

.toggle-sidebar-btn:hover {
  background: rgba(255, 255, 255, 0.15);
  transform: scale(1.05);
}

/* Bottom Hint & Audio control */
.interaction-hint {
  position: absolute;
  bottom: 20px;
  right: 20px;
  z-index: 9;
  font-size: 0.72rem;
  color: var(--text-muted);
  display: flex;
  align-items: center;
  gap: 8px;
  pointer-events: none;
}

.audio-btn {
  pointer-events: auto;
  background: rgba(139, 92, 246, 0.25);
  border: 1px solid var(--accent-purple);
  color: #fff;
  padding: 6px 12px;
  border-radius: 20px;
  font-size: 0.75rem;
  font-weight: 500;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 6px;
  transition: all 0.2s;
}

.audio-btn:hover {
  background: var(--accent-purple);
}

.audio-btn.playing {
  background: #ef4444;
  border-color: #f87171;
  animation: pulse-border 1.5s infinite;
}

@keyframes pulse-border {
  0% { box-shadow: 0 0 0 0 rgba(239, 68, 68, 0.5); }
  70% { box-shadow: 0 0 0 10px rgba(239, 68, 68, 0); }
  100% { box-shadow: 0 0 0 0 rgba(239, 68, 68, 0); }
}

/* Ripple indicator / tooltip */
.touch-ripple {
  position: absolute;
  width: 20px;
  height: 20px;
  border-radius: 50%;
  border: 2px solid var(--accent-cyan);
  transform: translate(-50%, -50%) scale(1);
  pointer-events: none;
  animation: ripple-anim 0.75s cubic-bezier(0.1, 0.8, 0.3, 1) forwards;
}

@keyframes ripple-anim {
  to {
    transform: translate(-50%, -50%) scale(4);
    opacity: 0;
  }
}

/* Responsive adjustments */
@media (max-width: 768px) {
  .controls-sidebar {
    width: calc(100vw - 32px);
    top: 70px;
    bottom: 16px;
    right: 16px;
  }
  .formula-hud {
    display: none; /* Hide on very small screens to avoid clutter */
  }
  .interaction-hint {
    left: 16px;
    right: auto;
  }
}