:root {
    /* Color variables */
    --bg-primary: #f8f9fa;
    --bg-secondary: #e9ecef;
    --bg-tertiary: #dee2e6;
    --text-primary: #212529;
    --text-secondary: #495057;
    --accent-primary: #7048e8;
    --accent-secondary: #5a32c7;
    --accent-tertiary: #4525a9;
    --success: #28a745;
    --warning: #ffc107;
    --danger: #dc3545;
    --info: #17a2b8;
    
    /* Spacing */
    --space-xs: 0.25rem;
    --space-sm: 0.5rem;
    --space-md: 1rem;
    --space-lg: 1.5rem;
    --space-xl: 2rem;
    
    /* Shadows */
    --shadow-sm: 0 2px 4px rgba(0,0,0,0.05);
    --shadow-md: 0 4px 8px rgba(0,0,0,0.1);
    --shadow-lg: 0 8px 16px rgba(0,0,0,0.15);
    
    /* Borders */
    --radius-sm: 4px;
    --radius-md: 8px;
    --radius-lg: 12px;
    --radius-full: 9999px;
    
    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-normal: 300ms ease;
  }
  
  .dark-theme {
    --bg-primary: #121212;
    --bg-secondary: #1e1e1e;
    --bg-tertiary: #2d2d2d;
    --text-primary: #f8f9fa;
    --text-secondary: #adb5bd;
    --accent-primary: #9775fa;
    --accent-secondary: #845ef7;
    --accent-tertiary: #7048e8;
  }
  
  * {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
  }
  
  body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.5;
    transition: background-color 0.3s, color 0.3s;
    overflow: hidden;
  }
  
  .app-container {
    display: flex;
    flex-direction: column;
    height: 100vh;
  }
  
  /* Header */
  header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--space-md);
    background-color: var(--bg-secondary);
    box-shadow: var(--shadow-sm);
    z-index: 10;
  }
  
  .brand {
    display: flex;
    align-items: center;
    gap: var(--space-md);
  }
  
  h1 {
    font-size: 1.5rem;
    font-weight: 600;
  }
  
  h2 {
    font-size: 1.2rem;
    font-weight: 500;
    margin-bottom: var(--space-md);
    padding-bottom: var(--space-xs);
    border-bottom: 1px solid var(--bg-tertiary);
  }
  
  /* Theme toggle */
  #theme-toggle {
    background: transparent;
    border: none;
    color: var(--text-primary);
    font-size: 1.25rem;
    cursor: pointer;
    padding: var(--space-sm);
    border-radius: var(--radius-md);
    display: flex;
    justify-content: center;
    align-items: center;
  }
  
  #theme-toggle:hover {
    background-color: var(--bg-tertiary);
  }
  
  #theme-toggle .fa-sun {
    display: none;
  }
  
  .dark-theme #theme-toggle .fa-moon {
    display: none;
  }
  
  .dark-theme #theme-toggle .fa-sun {
    display: block;
  }
  
  /* Main layout */
  main {
    display: flex;
    flex: 1;
    overflow: hidden;
  }
  
  .canvas-container {
    flex: 1;
    position: relative;
  }
  
  /* Control panel */
  .control-panel {
    width: 320px;
    background-color: var(--bg-secondary);
    box-shadow: var(--shadow-md);
    display: flex;
    flex-direction: column;
    transition: transform 0.3s ease;
  }
  
  /* Tabs */
  .tabs {
    display: flex;
    background-color: var(--bg-tertiary);
  }
  
  .tab-btn {
    flex: 1;
    padding: var(--space-md);
    background: transparent;
    border: none;
    color: var(--text-secondary);
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-fast);
    position: relative;
  }
  
  .tab-btn:hover {
    color: var(--text-primary);
  }
  
  .tab-btn.active {
    color: var(--accent-primary);
  }
  
  .tab-btn.active::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 20%;
    width: 60%;
    height: 3px;
    background-color: var(--accent-primary);
    border-radius: var(--radius-full);
  }
  
  .tab-content {
    flex: 1;
    overflow-y: auto;
    padding: var(--space-lg);
  }
  
  .tab-pane {
    display: none;
  }
  
  .tab-pane.active {
    display: block;
  }
  
  /* Shape selector */
  .shape-selector {
    display: flex;
    gap: var(--space-md);
    margin-bottom: var(--space-lg);
  }
  
  .shape-option {
    display: flex;
    flex-direction: column;
    align-items: center;
    cursor: pointer;
    padding: var(--space-sm);
    border-radius: var(--radius-md);
    border: 2px solid transparent;
    transition: all var(--transition-fast);
  }
  
  .shape-option:hover {
    background-color: var(--bg-tertiary);
  }
  
  .shape-option.selected {
    border-color: var(--accent-primary);
  }
  
  .shape-preview {
    width: 60px;
    height: 60px;
    margin-bottom: var(--space-sm);
    background-color: var(--bg-tertiary);
  }
  
  .shape-preview.round {
    border-radius: 50%;
  }
  
  .shape-preview.normal {
    border-radius: 30% 70% 70% 30% / 30% 30% 70% 70%;
  }
  
  .shape-preview.bizarre {
    border-radius: 60% 40% 30% 70% / 60% 30% 70% 40%;
  }
  
  /* Buttons */
  .btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: var(--space-sm) var(--space-md);
    border: none;
    border-radius: var(--radius-md);
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-fast);
  }
  
  .btn i {
    margin-right: var(--space-sm);
  }
  
  .primary-btn {
    background-color: var(--accent-primary);
    color: white;
  }
  
  .primary-btn:hover {
    background-color: var(--accent-secondary);
  }
  
  .secondary-btn {
    background-color: var(--bg-tertiary);
    color: var(--text-primary);
  }
  
  .secondary-btn:hover {
    background-color: var(--bg-tertiary);
    filter: brightness(0.95);
  }
  
  .button-group {
    display: flex;
    flex-direction: column;
    gap: var(--space-md);
  }
  
  /* Form elements */
  .form-group {
    margin-bottom: var(--space-lg);
  }
  
  .form-group label {
    display: block;
    margin-bottom: var(--space-sm);
    color: var(--text-secondary);
  }
  
  select {
    width: 100%;
    padding: var(--space-sm) var(--space-md);
    border: 1px solid var(--bg-tertiary);
    border-radius: var(--radius-md);
    background-color: var(--bg-primary);
    color: var(--text-primary);
    font-size: 1rem;
    appearance: none;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='24' height='24' viewBox='0 0 24 24' fill='none' stroke='currentColor' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpolyline points='6 9 12 15 18 9'%3E%3C/polyline%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 8px center;
    background-size: 16px;
  }
  
  input[type="text"] {
    width: 100%;
    padding: var(--space-sm) var(--space-md);
    border: 1px solid var(--bg-tertiary);
    border-radius: var(--radius-md);
    background-color: var(--bg-primary);
    color: var(--text-primary);
    font-size: 1rem;
  }
  
  input[type="color"] {
    width: 100%;
    height: 40px;
    border: none;
    border-radius: var(--radius-md);
    cursor: pointer;
    background-color: var(--bg-primary);
  }
  
  .color-presets {
    display: flex;
    gap: var(--space-sm);
    margin-top: var(--space-sm);
  }
  
  .color-preset {
    width: 30px;
    height: 30px;
    border-radius: 50%;
    border: 2px solid var(--bg-tertiary);
    cursor: pointer;
    transition: transform var(--transition-fast);
  }
  
  .color-preset:hover {
    transform: scale(1.1);
  }
  
  /* Toggle switch */
  .toggle-group {
    display: flex;
    flex-direction: column;
    gap: var(--space-md);
    margin-bottom: var(--space-lg);
  }
  
  .toggle {
    display: flex;
    align-items: center;
    cursor: pointer;
  }
  
  .toggle input {
    opacity: 0;
    width: 0;
    height: 0;
  }
  
  .slider {
    position: relative;
    display: inline-block;
    width: 40px;
    height: 20px;
    background-color: var(--bg-tertiary);
    border-radius: 20px;
    margin-right: var(--space-md);
    transition: background-color var(--transition-fast);
  }
  
  .slider:before {
    position: absolute;
    content: "";
    height: 16px;
    width: 16px;
    left: 2px;
    bottom: 2px;
    background-color: white;
    border-radius: 50%;
    transition: transform var(--transition-fast);
  }
  
  input:checked + .slider {
    background-color: var(--accent-primary);
  }
  
  input:checked + .slider:before {
    transform: translateX(20px);
  }
  
  /* File upload */
  .file-upload {
    margin-bottom: var(--space-lg);
  }
  
  input[type="file"] {
    display: none;
  }
  
  #file-name {
    margin-top: var(--space-sm);
    font-size: 0.875rem;
    color: var(--text-secondary);
  }
  
  /* Toast notifications */
  .toast {
    position: fixed;
    bottom: 24px;
    right: 24px;
    display: flex;
    align-items: center;
    padding: var(--space-md) var(--space-lg);
    background-color: var(--bg-secondary);
    color: var(--text-primary);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-lg);
    transform: translateY(100px);
    opacity: 0;
    transition: transform 0.3s, opacity 0.3s;
    z-index: 1000;
  }
  
  .toast.show {
    transform: translateY(0);
    opacity: 1;
  }
  
  .toast-icon {
    margin-right: var(--space-md);
    font-size: 1.2rem;
  }
  
  .toast.success .toast-icon::before {
    content: "✓";
    color: var(--success);
  }
  
  .toast.error .toast-icon::before {
    content: "✕";
    color: var(--danger);
  }
  
  .toast.info .toast-icon::before {
    content: "ℹ";
    color: var(--info);
  }
  
  /* Responsive styles */
  @media (max-width: 768px) {
    main {
      flex-direction: column;
    }
    
    .control-panel {
      width: 100%;
      height: 50%;
    }
    
    .canvas-container {
      height: 50%;
    }
    
    .shape-selector {
      justify-content: center;
    }
  }