/* Core Styling Variables */
:root {
  --bg-primary: #0a0a0c;
  --bg-viewport: #060608;
  --bg-sidebar: rgba(18, 18, 22, 0.85);
  --bg-glass: rgba(22, 22, 28, 0.65);
  --border-color: rgba(255, 255, 255, 0.08);
  --border-glow: rgba(0, 242, 254, 0.4);
  --color-accent: #00f2fe;
  --color-accent-pink: #ec4899;
  --text-main: #f8fafc;
  --text-muted: #94a3b8;
  --color-error: #f43f5e;
  --color-success: #10b981;
  --font-sans: 'Inter', 'Tajawal', sans-serif;
  --font-mono: 'JetBrains Mono', monospace;
}

/* Reset and Layout */
* {
  box-sizing: border-box;
}

body {
  font-family: var(--font-sans);
  background-color: var(--bg-primary);
  color: var(--text-main);
  padding: 0;
  margin: 0;
  overflow: hidden;
  -webkit-font-smoothing: antialiased;
}

.app-layout {
  display: flex;
  width: 100vw;
  height: 100vh;
  height: 100dvh;
  position: relative;
}

/* Viewport Area */
.viewport-area {
  flex: 1;
  min-width: 0;
  height: 100%;
  position: relative;
  display: flex;
  justify-content: center;
  align-items: center;
  background-color: var(--bg-viewport);
  overflow: hidden;
}

#canvasContainer {
  position: relative;
  width: 100%;
  height: 100%;
  display: flex;
  justify-content: center;
  align-items: center;
}

canvas {
  display: block;
  border: none;
}

/* Floating Glassmorphic Header */
.floating-header {
  position: absolute;
  top: 20px;
  left: 50%;
  transform: translateX(-50%);
  z-index: 10;
  width: 90%;
  max-width: 500px;
  background: var(--bg-glass);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border: 1px solid var(--border-color);
  border-radius: 16px;
  padding: 12px 20px;
  text-align: center;
  box-shadow: 0 10px 25px rgba(0, 0, 0, 0.3);
  transition: border-color 0.3s ease, box-shadow 0.3s ease;
}

.floating-header.valid-pulse {
  border-color: var(--color-success);
  box-shadow: 0 0 15px rgba(16, 185, 129, 0.3), 0 10px 25px rgba(0, 0, 0, 0.3);
}

.floating-header.has-error {
  border-color: var(--color-error);
  box-shadow: 0 0 15px rgba(244, 63, 94, 0.3), 0 10px 25px rgba(0, 0, 0, 0.3);
}

.app-title {
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.15em;
  color: var(--text-muted);
  margin: 0 0 8px 0;
  font-weight: 600;
}

.function-panel {
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 1.35rem;
  font-family: var(--font-mono);
  color: var(--text-main);
  gap: 0;
}

.fn-notation {
  color: var(--text-muted);
  font-size: 1.1rem;
  margin-right: 6px;
}

.fn-bracket {
  color: var(--color-accent);
  font-weight: 500;
}

.fn-comma {
  color: var(--text-muted);
  margin-right: 2px;
}

.fn-part {
  cursor: pointer;
  display: inline-block;
  padding: 2px 6px;
  border-radius: 6px;
  border: 1px dashed transparent;
  transition: background-color 0.2s, border-color 0.2s;
  min-width: 25px;
}

.fn-part:hover, .fn-part:focus {
  background-color: rgba(0, 242, 254, 0.08);
  border-color: var(--border-glow);
  outline: none;
}

/* Custom Math Equation Input Box */
.fn-edit {
  color: var(--color-accent);
  background-color: rgba(0, 0, 0, 0.3) !important;
  border: 1px solid var(--color-accent) !important;
  border-radius: 6px;
  padding: 2px 6px;
  font-family: var(--font-mono);
  font-size: 1.2rem;
  text-align: center;
  outline: none;
  box-shadow: 0 0 8px rgba(0, 242, 254, 0.2);
}

.fn-edit.input-error {
  color: var(--color-error);
  border-color: var(--color-error) !important;
  box-shadow: 0 0 8px rgba(244, 63, 94, 0.2);
}

/* Error Panel inside Header */
.error-panel {
  max-height: 0;
  opacity: 0;
  overflow: hidden;
  color: var(--color-error);
  font-size: 0.75rem;
  font-family: var(--font-mono);
  margin-top: 0;
  text-align: center;
  transition: max-height 0.3s ease, opacity 0.3s ease, margin-top 0.3s ease;
}

.error-panel.visible {
  max-height: 80px;
  opacity: 1;
  margin-top: 8px;
  padding-top: 6px;
  border-top: 1px solid rgba(244, 63, 94, 0.15);
}

/* HUD elements on canvas */
.hud-btn {
  z-index: 9;
  width: 44px;
  height: 44px;
  border-radius: 12px;
  background: var(--bg-glass);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  font-size: 1.1rem;
  display: none;
  justify-content: center;
  align-items: center;
  cursor: pointer;
  box-shadow: 0 4px 15px rgba(0, 0, 0, 0.25);
  transition: background-color 0.2s, border-color 0.2s, color 0.2s;
}

.hud-btn:hover {
  background-color: rgba(255, 255, 255, 0.1);
  border-color: var(--color-accent);
  color: var(--color-accent);
}

.hud-overlay {
  position: absolute;
  bottom: 92px;
  left: 20px;
  background: rgba(0, 0, 0, 0.75);
  border: 1px solid var(--border-color);
  padding: 6px 12px;
  border-radius: 8px;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--color-accent);
  letter-spacing: 0.05em;
  opacity: 0;
  transform: translateY(10px);
  transition: opacity 0.3s ease, transform 0.3s ease;
  pointer-events: none;
  z-index: 5;
}

.hud-overlay.visible {
  opacity: 1;
  transform: translateY(0);
}

.hud-overlay-center {
  position: absolute;
  top: 55%;
  left: 50%;
  transform: translate(-50%, -50%);
  background: rgba(0, 0, 0, 0.6);
  backdrop-filter: blur(4px);
  -webkit-backdrop-filter: blur(4px);
  border: 1px solid var(--border-color);
  padding: 12px 24px;
  border-radius: 12px;
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--text-muted);
  pointer-events: none;
  opacity: 0;
  transition: opacity 0.3s ease;
  z-index: 5;
  text-align: center;
  box-shadow: 0 4px 15px rgba(0,0,0,0.2);
}

.hud-overlay-center.visible {
  opacity: 1;
}

/* Sidebar Settings Panel */
.sidebar {
  width: 320px;
  height: 100%;
  background: var(--bg-sidebar);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-left: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  z-index: 20;
  transition: transform 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  flex-shrink: 0;
}

.sidebar-header {
  padding: 24px;
  border-bottom: 1px solid var(--border-color);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.sidebar-header h2 {
  font-size: 1.1rem;
  font-weight: 600;
  letter-spacing: 0.02em;
  margin: 0;
}

.close-btn {
  background: none;
  border: none;
  color: var(--text-muted);
  font-size: 1.75rem;
  cursor: pointer;
  line-height: 1;
  padding: 0;
  display: none; /* Only visible on mobile overlay */
  transition: color 0.2s;
}

.close-btn:hover {
  color: var(--color-error);
}

.sidebar-body {
  flex: 1;
  overflow-y: auto;
  padding: 24px;
}

/* Styled Scrollbar for Sidebar */
.sidebar-body::-webkit-scrollbar {
  width: 6px;
}
.sidebar-body::-webkit-scrollbar-track {
  background: transparent;
}
.sidebar-body::-webkit-scrollbar-thumb {
  background: rgba(255, 255, 255, 0.1);
  border-radius: 3px;
}
.sidebar-body::-webkit-scrollbar-thumb:hover {
  background: rgba(255, 255, 255, 0.2);
}

.sidebar-section {
  margin-bottom: 28px;
}

.sidebar-section label {
  display: block;
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-muted);
  margin-bottom: 12px;
  font-weight: 600;
}

/* Custom Select Dropdown */
.select-container {
  position: relative;
  width: 100%;
}

.select-container select {
  width: 100%;
  background: rgba(0, 0, 0, 0.2);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 10px 14px;
  color: var(--text-main);
  font-family: var(--font-mono);
  font-size: 0.85rem;
  outline: none;
  cursor: pointer;
  appearance: none;
  -webkit-appearance: none;
  transition: border-color 0.2s, box-shadow 0.2s;
}

.select-container select:focus {
  border-color: var(--color-accent);
  box-shadow: 0 0 8px rgba(0, 242, 254, 0.15);
}

.select-container::after {
  content: '\25BC';
  position: absolute;
  right: 14px;
  top: 50%;
  transform: translateY(-50%) scale(0.8);
  color: var(--text-muted);
  pointer-events: none;
  font-size: 0.7rem;
}

/* Floating Simulation Actions */
.action-tray {
  position: absolute;
  bottom: 0;
  left: 50%;
  transform: translateX(-50%);
  z-index: 10;
  width: 100%;
  padding: 10px 12px;
  background: var(--bg-glass);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-top: 1px solid var(--border-color);
  box-shadow: 0 10px 25px rgba(0, 0, 0, 0.3);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.action-buttons {
  display: flex;
  gap: 8px;
}

.btn {
  display: inline-flex;
  justify-content: center;
  align-items: center;
  gap: 8px;
  padding: 10px 12px;
  border-radius: 8px;
  font-weight: 500;
  font-size: 0.8rem;
  cursor: pointer;
  transition: all 0.2s ease;
  border: 1px solid transparent;
  outline: none;
  text-align: center;
}

.btn-action {
  background: rgba(255, 255, 255, 0.04);
  border: 1px solid var(--border-color);
  color: var(--text-main);
}

.btn-action:hover {
  background: rgba(255, 255, 255, 0.08);
}

#playPause.btn-action:hover {
  border-color: var(--color-success);
  color: var(--color-success);
  background: rgba(16, 185, 129, 0.05);
}

#playPause.btn-action.active {
  border-color: var(--color-accent-pink);
  color: var(--color-accent-pink);
  background: rgba(236, 72, 153, 0.08);
  box-shadow: 0 0 10px rgba(236, 72, 153, 0.15);
}

#respawnParticles:hover {
  border-color: var(--color-accent);
  color: var(--color-accent);
  background: rgba(0, 242, 254, 0.05);
}

#clearParticles:hover {
  border-color: var(--color-error);
  color: var(--color-error);
  background: rgba(244, 63, 94, 0.05);
}

.toggle-buttons {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
}

.btn-toggle {
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid var(--border-color);
  color: var(--text-muted);
}

.btn-toggle:hover {
  color: var(--text-main);
  background: rgba(255, 255, 255, 0.06);
}

.btn-toggle.active {
  background: rgba(0, 242, 254, 0.06);
  border-color: var(--color-accent);
  color: var(--color-accent);
  box-shadow: 0 0 10px rgba(0, 242, 254, 0.1);
}

/* Custom Styled Range Sliders */
.parameter-slider {
  margin-bottom: 20px;
}

.slider-info {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-bottom: 8px;
}

.slider-info span:first-child {
  font-weight: 500;
}

.slider-info span:last-child {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--color-accent);
}

input[type="range"] {
  -webkit-appearance: none;
  width: 100%;
  height: 6px;
  background: rgba(255, 255, 255, 0.08);
  border-radius: 3px;
  outline: none;
  margin: 8px 0;
}

input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: var(--color-accent);
  cursor: pointer;
  box-shadow: 0 0 8px rgba(0, 242, 254, 0.5);
  transition: transform 0.1s, background-color 0.2s;
}

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

input[type="range"]::-moz-range-thumb {
  width: 16px;
  height: 16px;
  border: none;
  border-radius: 50%;
  background: var(--color-accent);
  cursor: pointer;
  box-shadow: 0 0 8px rgba(0, 242, 254, 0.5);
  transition: transform 0.1s, background-color 0.2s;
}

input[type="range"]::-moz-range-thumb:hover {
  transform: scale(1.2);
  background-color: #fff;
}

/* Sidebar Footer */
.sidebar-footer {
  padding: 20px 24px;
  border-top: 1px solid var(--border-color);
  display: flex;
  justify-content: flex-end;
  align-items: center;
  gap: 16px;
}

.sidebar-footer-action {
  padding: 0;
  background: none;
  border: 0;
  color: var(--text-muted);
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-size: 1rem;
  line-height: 1;
  cursor: pointer;
  transition: color 0.2s;
}

.sidebar-footer-action:hover,
.sidebar-footer-action:focus-visible {
  color: var(--color-accent);
  outline: none;
}

/* ==========================================================================
   Responsive / Device Layout Styles
   ========================================================================== */

/* Mobile Screens (< 768px): Full-Screen Experience */
@media (max-width: 767px) {
  .app-layout {
    flex-direction: column;
  }

  .viewport-area {
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
  }

  /* Adjust floating header width and size */
  .floating-header {
    top: calc(15px + env(safe-area-inset-top));
    width: 92%;
    padding: 8px 16px;
  }

  .hud-btn {
    display: flex;
    flex-shrink: 0;
  }

  .app-title {
    font-size: 0.7rem;
    margin-bottom: 4px;
  }

  .function-panel {
    font-size: 1.15rem;
  }

  .fn-notation {
    font-size: 0.95rem;
  }

  .hud-overlay {
    left: calc(15px + env(safe-area-inset-left));
    bottom: calc(84px + env(safe-area-inset-bottom));
  }

  .action-tray {
    bottom: 0;
    padding: 7px 8px;
  }

  .action-tray .btn {
    width: 42px;
    height: 42px;
    padding: 0;
    font-size: 1rem;
  }

  .action-tray .btn span {
    display: none;
  }

  /* Control Drawer Overlay style for mobile */
  .sidebar {
    position: absolute;
    right: 0;
    top: 0;
    height: 100%;
    transform: translateX(100%);
    box-shadow: -10px 0 30px rgba(0, 0, 0, 0.6);
    background: rgba(14, 14, 18, 0.95);
    z-index: 100;
  }

  .sidebar.open {
    transform: translateX(0);
  }

  .close-btn {
    display: block; /* Close button available in sidebar drawer on mobile */
  }
}