:root {
    /* Professional Color Palette */
    --primary: #0f172a;       /* Slate 900 */
    --primary-light: #334155; /* Slate 700 */
    --accent: #2563eb;        /* Royal Blue */
    --accent-hover: #1d4ed8;
    --bg-body: #f1f5f9;       /* Slate 100 */
    --bg-card: #ffffff;
    --border: #cbd5e1;
    --text-main: #1e293b;
    --text-muted: #64748b;
    --success-bg: #ecfdf5;
    --success-text: #047857;
    --focus-ring: rgba(37, 99, 235, 0.2);
  }
  
  * {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
  }
  
  body {
    font-family: 'Inter', system-ui, -apple-system, sans-serif;
    background-color: var(--bg-body);
    color: var(--text-main);
    line-height: 1.5;
    -webkit-font-smoothing: antialiased;
  }
  
  /* Layout Grid */
  .app-layout {
    display: flex;
    flex-direction: column;
    min-height: 100vh;
  }
  
  .main-container {
    display: flex;
    justify-content: center;
    gap: 20px;
    padding: 20px;
    max-width: 1280px;
    margin: 0 auto;
    width: 100%;
  }
  
  /* Ads - Subtle placeholders */
  .ad-banner-top {
    width: 100%;
    display: flex;
    justify-content: center;
    padding: 10px;
    background: #e2e8f0;
  }
  
  .ad-slot {
    width: 728px;
    height: 90px;
    background: #cbd5e1;
    display: flex;
    align-items: center;
    justify-content: center;
    color: #64748b;
    font-size: 0.8rem;
    border-radius: 4px;
  }
  
  .ad-sidebar {
    display: none; /* Hidden on mobile by default */
  }
  
  /* Calculator Card */
  .calculator-wrapper {
    flex: 1;
    max-width: 600px;
  }
  
  .calculator-card {
    background: var(--bg-card);
    border-radius: 12px;
    padding: 24px;
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    border: 1px solid #e2e8f0;
  }
  
  .calc-header {
    text-align: center;
    margin-bottom: 32px;
  }
  
  .calc-header h1 {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary);
    margin-bottom: 8px;
  }
  
  .calc-header p {
    color: var(--text-muted);
    font-size: 0.95rem;
  }
  
  /* Form Styling */
  .calc-form {
    display: flex;
    flex-direction: column;
    gap: 24px;
  }
  
  .highlight-section {
    background: #f8fafc;
    padding: 16px;
    border-radius: 8px;
    border: 1px solid var(--border);
  }
  
  .section-label {
    display: block;
    font-weight: 600;
    font-size: 0.9rem;
    margin-bottom: 8px;
    color: var(--primary);
  }
  
  /* Inputs & Selects */
  .select-wrapper {
    position: relative;
  }
  
  select, input {
    width: 100%;
    padding: 12px 16px;
    border: 1px solid var(--border);
    border-radius: 8px;
    font-size: 1rem;
    color: var(--text-main);
    background: #fff;
    transition: all 0.2s ease;
    appearance: none; /* Removes default OS styling */
  }
  
  input {
    padding-right: 40px; /* Space for units */
  }
  
  select:focus, input:focus {
    outline: none;
    border-color: var(--accent);
    box-shadow: 0 0 0 3px var(--focus-ring);
  }
  
  .select-arrow {
    position: absolute;
    right: 16px;
    top: 50%;
    transform: translateY(-50%);
    pointer-events: none;
    font-size: 0.7rem;
    color: var(--text-muted);
  }
  
  .form-divider {
    display: flex;
    align-items: center;
    text-align: center;
    color: var(--text-muted);
    font-size: 0.85rem;
    font-weight: 500;
    text-transform: uppercase;
    letter-spacing: 0.05em;
  }
  
  .form-divider::before, .form-divider::after {
    content: '';
    flex: 1;
    border-bottom: 1px solid #e2e8f0;
  }
  
  .form-divider span {
    padding: 0 10px;
  }
  
  /* Grid for Technical Specs */
  .specs-grid {
    display: grid;
    grid-template-columns: 1fr; /* Mobile default: 1 column */
    gap: 20px;
  }
  
  .input-group {
    display: flex;
    flex-direction: column;
    gap: 6px;
  }
  
  .input-group label {
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--primary-light);
  }
  
  .input-wrapper {
    position: relative;
    display: flex;
    align-items: center;
  }
  
  .unit {
    position: absolute;
    right: 16px;
    color: var(--text-muted);
    font-size: 0.9rem;
    pointer-events: none;
  }
  
  .hint {
    font-size: 0.8rem;
    color: var(--text-muted);
  }
  
  /* Button */
  .calculate-btn {
    background-color: var(--accent);
    color: white;
    border: none;
    padding: 16px;
    border-radius: 8px;
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    transition: background-color 0.2s;
    margin-top: 10px;
  }
  
  .calculate-btn:hover {
    background-color: var(--accent-hover);
  }
  
  .calculate-btn:active {
    transform: translateY(1px);
  }
  
  /* Result Box */
  .result-box {
    margin-top: 24px;
    background-color: var(--success-bg);
    border: 1px solid var(--success-text);
    border-radius: 8px;
    padding: 24px;
    text-align: center;
    color: var(--success-text);
    opacity: 0;
    transform: translateY(10px);
    transition: all 0.3s ease;
  }
  
  .result-box.visible {
    opacity: 1;
    transform: translateY(0);
  }
  
  .result-time {
    display: block;
    font-size: 2rem;
    font-weight: 700;
    line-height: 1.2;
    margin-bottom: 4px;
  }
  
  .result-details {
    font-size: 0.95rem;
    opacity: 0.9;
  }
  
  /* Content Area */
  .info-content {
    margin-top: 40px;
    padding: 0 10px;
  }
  
  .info-content h2 {
    font-size: 1.25rem;
    color: var(--primary);
    margin-bottom: 16px;
  }
  
  .formula-card {
    background: #e2e8f0;
    padding: 16px;
    border-radius: 6px;
    font-family: monospace;
    font-size: 0.9rem;
    color: var(--primary);
    margin-bottom: 24px;
    border-left: 4px solid var(--accent);
    overflow-x: auto;
  }
  
  .faq-grid details {
    background: white;
    border: 1px solid var(--border);
    border-radius: 8px;
    margin-bottom: 10px;
    overflow: hidden;
  }
  
  .faq-grid summary {
    padding: 16px;
    font-weight: 600;
    cursor: pointer;
    list-style: none; /* Hides default triangle */
    position: relative;
    padding-right: 40px;
  }
  
  .faq-grid summary::after {
    content: '+';
    position: absolute;
    right: 16px;
    font-size: 1.2rem;
    color: var(--accent);
  }
  
  .faq-grid details[open] summary::after {
    content: '-';
  }
  
  .faq-grid p {
    padding: 0 16px 16px 16px;
    color: var(--text-muted);
    font-size: 0.95rem;
  }
  
  /* Responsive Breakpoints */
  @media (min-width: 768px) {
    .specs-grid {
      grid-template-columns: 1fr 1fr; /* 2 Columns on tablet+ */
    }
  
    .ad-sidebar {
      display: block;
      width: 160px;
      flex-shrink: 0;
    }
    
    .ad-slot-vertical {
      width: 160px;
      height: 600px;
      background: #e2e8f0;
      display: flex;
      justify-content: center;
      align-items: center;
      color: #94a3b8;
      position: sticky;
      top: 20px;
    }
  
    .calc-header h1 {
      font-size: 2rem;
    }
  
    .calculator-card {
      padding: 40px;
    }
  }
  
  .hidden {
    display: none;
  }

  .table-responsive {
    overflow-x: auto;
    margin: 20px 0;
    border-radius: 8px;
    border: 1px solid var(--border);
  }
  
  .wattage-table {
    width: 100%;
    border-collapse: collapse;
    background: white;
    font-size: 0.95rem;
  }
  
  .wattage-table th {
    background: var(--primary-light);
    color: white;
    text-align: left;
    padding: 12px 16px;
    font-weight: 600;
  }
  
  .wattage-table td {
    padding: 12px 16px;
    border-bottom: 1px solid #f1f5f9;
    color: var(--text-main);
  }
  
  .wattage-table tr:last-child td {
    border-bottom: none;
  }
  
  .wattage-table tr:nth-child(even) {
    background-color: #f8fafc;
  }
  
  /* SEO Text Styling */
  .seo-text h3 {
    margin-top: 32px;
    margin-bottom: 12px;
    font-size: 1.2rem;
    color: var(--primary);
  }
  
  .seo-text p {
    color: var(--text-muted);
    margin-bottom: 16px;
    line-height: 1.6;
  }
  
  .hint {
    display: block;
    margin-top: 4px;
    font-size: 0.8rem;
    color: var(--text-muted);
  }

  /* Footer SEO & Layout */
  .site-footer {
    background: #e2e8f0;
    padding: 32px 20px;
    margin-top: auto; /* Pushes footer to bottom of flex container */
    text-align: center;
    border-top: 1px solid var(--border);
  }
  
  .footer-content p {
    color: var(--text-muted);
    font-size: 0.9rem;
    margin-bottom: 12px;
  }
  
  .footer-links a {
    color: var(--primary-light);
    text-decoration: none;
    margin: 0 8px;
    font-size: 0.85rem;
  }
  
  .footer-links a:hover {
    text-decoration: underline;
    color: var(--accent);
  }