:root {
    --primary: #6c5ce7;
    --primary-light: #a29bfe;
    --secondary: #00cec9;
    --dark: #2d3436;
    --light: #f5f6fa;
    --gray: #dfe6e9;
    --shadow: 0 10px 20px rgba(0, 0, 0, 0.1);
    --transition: all 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
  }
  
  body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    background-color: var(--light);
    color: var(--dark);
    line-height: 1.6;
  }
  
  #main_holder {
    width: 90%;
    max-width: 1200px;
    margin: 80px auto;
    display: flex;
    flex-direction: column;
    gap: 2rem;
  }
  
  /* Modern Book Page Design */
  #text_holder {
    position: relative;
    background: white;
    border-radius: 12px;
    box-shadow: var(--shadow);
    padding: 3rem;
    min-height: 500px;
    overflow: hidden;
    display: flex;
  }
  
  #text_holder::before {
    content: "";
    position: absolute;
    top: 0;
    left: 60px;
    width: 2px;
    height: 100%;
    background: var(--gray);
  }
  
  #input_holder {
    width: 100%;
    min-height: 100%;
    flex: 1;
    border: none;
    resize: none;
    font-size: 1.1rem;
    line-height: 1.8;
    padding: 0 3rem;
    font-family: 'Source Serif Pro', serif;
    color: var(--dark);
    background: transparent;
  }
  
  #input_holder:focus {
    outline: none;
  }
  
  /* Control Panel */
  .control-panel {
    background: white;
    border-radius: 12px;
    padding: 2rem;
    box-shadow: var(--shadow);
  }
  
  .button {
    background: var(--primary);
    color: white;
    border: none;
    padding: 12px 24px;
    border-radius: 8px;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    display: flex;
    align-items: center;
    gap: 8px;
  }
  
  .button:hover {
    background: var(--primary-light);
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(108, 92, 231, 0.3);
  }
  
  .button.secondary {
    background: var(--gray);
    color: var(--dark);
  }
  
  .button.secondary:hover {
    background: #c8d6e5;
  }
  
  .button-group {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
  }
  
  /* Form Elements */
  .select-wrapper, .range-wrapper {
    margin-bottom: 1.5rem;
  }
  
  label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 600;
    color: var(--dark);
  }
  
  select, input[type="range"] {
    width: 100%;
  }
  
  select {
    padding: 12px;
    border: 2px solid var(--gray);
    border-radius: 8px;
    font-size: 1rem;
    transition: var(--transition);
  }
  
  select:focus {
    outline: none;
    border-color: var(--primary);
  }
  
  input[type="range"] {
    -webkit-appearance: none;
    height: 6px;
    background: var(--gray);
    border-radius: 3px;
    margin-top: 1rem;
  }
  
  input[type="range"]::-webkit-slider-thumb {
    -webkit-appearance: none;
    width: 20px;
    height: 20px;
    background: var(--primary);
    border-radius: 50%;
    cursor: pointer;
    transition: var(--transition);
  }
  
  input[type="range"]::-webkit-slider-thumb:hover {
    transform: scale(1.1);
  }
  
  /* Page Navigation */
  .page-navigation {
    display: none;
    background: white;
    border-radius: 12px;
    padding: 1.5rem;
    box-shadow: var(--shadow);
    align-items: center;
    gap: 1rem;
    flex-wrap: wrap;
  }
  
  .toggle-container {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    margin-left: auto;
  }
  
  /* Responsive */
  @media (max-width: 768px) {
    #main_holder {
      width: 95%;
      margin: 60px auto;
    }
    
    #text_holder {
      padding: 2rem 1.5rem;
    }
    
    #input_holder {
      padding: 0 1.5rem;
    }
    
    #text_holder::before {
      left: 40px;
    }
    
    .button-group {
      flex-direction: column;
    }
    
    .button {
      width: 100%;
      justify-content: center;
    }
  }