:root {
    --primary-blue: #0052cc;
    --hero-gradient: linear-gradient(135deg, #0061ff 0%, #0033aa 100%);
    --bg-light: #f8fafc;
    --white: #ffffff;
    --text-main: #1e293b;
    --text-muted: #64748b;
    --border-color: #e2e8f0;
    --shadow-sm: 0 2px 4px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    --radius: 12px;
    --transition: all 0.3s ease;
    --success-bg: #ecfdf5;
    --success-text: #047857;
    --warning-bg: #fff7ed;
    --warning-text: #c2410c;
    --danger-bg: #fef2f2;
    --danger-text: #b91c1c;
  }
  
  /*-------------------------------------------------------------------------------------
                                          BASE
  --------------------------------------------------------------------------------------*/
  * {
    box-sizing: border-box;
  }
  
  html {
    scroll-behavior: smooth;
  }
  
  body {
    font-family: "Inter", sans-serif;
    color: var(--text-main);
    background: var(--white);
    line-height: 1.7;
  }
  
  img {
    max-width: 100%;
    display: block;
  }
  
  a {
    color: var(--primary-blue);
    text-decoration: none;
    transition: var(--transition);
  }
  
  a:hover {
    opacity: 0.9;
  }
  
  .section-padding {
    padding: 72px 0;
  }
  
  .bg-light {
    background: var(--bg-light);
  }
  
  .left-align {
    text-align: left;
  }
  
  .section-header {
    max-width: 860px;
    margin-bottom: 28px;
  }
  
  .section-header h2 {
    font-size: clamp(1.8rem, 3vw, 2.5rem);
    line-height: 1.2;
    margin-bottom: 12px;
  }
  
  .section-header p {
    color: var(--text-muted);
    margin: 0;
  }
  
  .prose {
    max-width: 900px;
  }
  
  .prose p:last-child {
    margin-bottom: 0;
  }
  
  .top-spacer {
    margin-top: 22px;
  }
  
  .hidden {
    display: none !important;
  }
  
  /*-------------------------------------------------------------------------------------
                                          HERO
  --------------------------------------------------------------------------------------*/
  .hero {
    background: var(--hero-gradient);
    color: var(--white);
    padding: 40px 0 40px;
  }
  
  .hero-content {
    display: block;
  }
  
  .breadcrumb {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    font-size: 0.95rem;
    margin-bottom: 28px;
    opacity: 0.92;
  }
  
  .breadcrumb a,
  .breadcrumb span {
    color: rgba(255, 255, 255, 0.92);
  }
  
  .hero-text {
    max-width: 900px;
  }
  
  .hero h1 {
    font-size: clamp(2.2rem, 5vw, 3.8rem);
    line-height: 1.1;
    margin: 0 0 18px;
  }
  
  /*-------------------------------------------------------------------------------------
                                          BUTTONS
  --------------------------------------------------------------------------------------*/
  .btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-height: 48px;
    padding: 0 22px;
    border-radius: 10px;
    font-weight: 700;
    border: 1px solid transparent;
    cursor: pointer;
    transition: var(--transition);
    text-decoration: none;
    line-height: 1;
  }
  
  .btn-primary {
    background: var(--primary-blue);
    color: var(--white);
    box-shadow: var(--shadow-sm);
    border-color: var(--white);
  }
  
  .btn-primary:hover {
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
  }
  
  .btn-secondary {
    background: rgba(255, 255, 255, 0.14);
    color: var(--white);
    border-color: rgba(255, 255, 255, 0.2);
  }
  
  .btn-secondary:hover {
    background: rgba(255, 255, 255, 0.22);
  }
  
  .btn-light {
    background: var(--white);
    color: var(--text-main);
    border: 1px solid var(--border-color);
  }
  
  /*-------------------------------------------------------------------------------------
                                      CALCULATOR
  --------------------------------------------------------------------------------------*/
  .calculator-grid {
    display: grid;
    grid-template-columns: 1.08fr 0.92fr;
    gap: 24px;
    align-items: start;
  }
  
  .calculator-card {
    background: var(--white);
    border: 1px solid var(--border-color);
    border-radius: 18px;
    box-shadow: var(--shadow-sm);
    padding: 26px;
  }
  
  .calculator-card h3 {
    font-size: 1.35rem;
    margin-bottom: 10px;
  }
  
  .card-intro {
    color: var(--text-muted);
    margin-bottom: 20px;
  }
  
  .form-grid {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 16px;
  }
  
  .form-group {
    display: flex;
    flex-direction: column;
    gap: 8px;
  }
  
  .form-group label {
    font-weight: 600;
    font-size: 0.95rem;
    color: var(--text-main);
  }
  
  .form-group input,
  .form-group select {
    width: 100%;
    min-height: 48px;
    padding: 12px 14px;
    border: 1px solid var(--border-color);
    border-radius: 10px;
    font-family: inherit;
    font-size: 0.98rem;
    color: var(--text-main);
    background: var(--white);
    transition: var(--transition);
  }
  
  .form-group input:focus,
  .form-group select:focus {
    outline: none;
    border-color: var(--primary-blue);
    box-shadow: 0 0 0 3px rgba(0, 82, 204, 0.12);
  }
  
  .helper-note {
    margin-top: 18px;
    padding: 14px 16px;
    border-radius: 12px;
    background: #f8fbff;
    border: 1px solid #d9e7ff;
  }
  
  .helper-note p {
    margin: 0 0 8px;
    color: var(--text-muted);
    font-size: 0.93rem;
  }
  
  .helper-note p:last-child {
    margin-bottom: 0;
  }
  
  .button-row {
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
    margin-top: 22px;
  }
  
  .form-message {
    border-radius: 10px;
    padding: 12px 14px;
    margin-bottom: 16px;
    font-size: 0.95rem;
  }
  
  .error-message {
    background: var(--danger-bg);
    color: var(--danger-text);
    border: 1px solid #fecaca;
  }
  
  /*-------------------------------------------------------------------------------------
                                      RESULTS
  --------------------------------------------------------------------------------------*/
  .results-placeholder {
    min-height: 360px;
    display: grid;
    place-items: center;
    text-align: center;
    padding: 24px;
    border: 1px dashed var(--border-color);
    border-radius: 14px;
    color: var(--text-muted);
    background: #fbfdff;
  }
  
  .results-placeholder i {
    font-size: 2.25rem;
    color: var(--primary-blue);
    margin-bottom: 12px;
  }
  
  .results-content {
    display: grid;
    gap: 18px;
  }
  
  .status-banner {
    border-radius: 14px;
    padding: 16px 18px;
    border: 1px solid transparent;
  }
  
  .status-banner.general {
    background: #eff6ff;
    color: #1d4ed8;
    border-color: #bfdbfe;
  }
  
  .status-banner.success {
    background: var(--success-bg);
    color: var(--success-text);
    border-color: #a7f3d0;
  }
  
  .status-banner.warning {
    background: var(--warning-bg);
    color: var(--warning-text);
    border-color: #fed7aa;
  }
  
  .status-banner.danger {
    background: var(--danger-bg);
    color: var(--danger-text);
    border-color: #fecaca;
  }
  
  .status-badge {
    display: inline-block;
    font-size: 0.8rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    margin-bottom: 8px;
  }
  
  .status-banner p {
    margin: 0;
    line-height: 1.6;
  }
  
  .results-summary-grid {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 14px;
  }
  
  .summary-item {
    border: 1px solid var(--border-color);
    border-radius: 14px;
    padding: 16px;
    background: var(--white);
  }
  
  .summary-item.accent {
    background: #f8fbff;
    border-color: #d9e7ff;
  }
  
  .summary-item .label {
    display: block;
    font-size: 0.88rem;
    color: var(--text-muted);
    margin-bottom: 8px;
  }
  
  .summary-item strong {
    font-size: 1.2rem;
    line-height: 1.25;
    display: block;
    word-break: break-word;
  }
  
  .comparison-panel,
  .snapshot-card,
  .formula-summary-card,
  .interpretation-card,
  .recommendation-card {
    border: 1px solid var(--border-color);
    border-radius: 14px;
    padding: 18px;
    background: var(--white);
  }
  
  .comparison-panel h4,
  .snapshot-card h4,
  .formula-summary-card h4,
  .interpretation-card h4,
  .recommendation-card h4 {
    margin-bottom: 14px;
    font-size: 1.02rem;
  }
  
  .comparison-bars {
    display: grid;
    gap: 14px;
  }
  
  .bar-row {
    display: grid;
    grid-template-columns: 120px 1fr auto;
    gap: 12px;
    align-items: center;
  }
  
  .bar-row span,
  .bar-row strong {
    font-size: 0.92rem;
  }
  
  .bar-track {
    width: 100%;
    height: 12px;
    border-radius: 999px;
    background: #e2e8f0;
    overflow: hidden;
  }
  
  .bar-fill {
    height: 100%;
    width: 0;
    border-radius: 999px;
    transition: width 0.5s ease;
  }
  
  .bar-fill.before {
    background: #3b82f6;
  }
  
  .bar-fill.after {
    background: #10b981;
  }
  
  .bar-fill.neutral {
    background: #8b5cf6;
  }
  
  .snapshot-row {
    display: flex;
    justify-content: space-between;
    gap: 16px;
    padding: 10px 0;
    border-bottom: 1px solid var(--border-color);
  }
  
  .snapshot-row:last-child {
    border-bottom: 0;
    padding-bottom: 0;
  }
  
  .snapshot-row span {
    color: var(--text-muted);
  }
  
  .snapshot-row strong {
    text-align: right;
  }
  
  .formula-summary-card p,
  .interpretation-card p,
  .recommendation-card p {
    margin: 0;
    color: var(--text-main);
  }
  
  /*-------------------------------------------------------------------------------------
                                  GENERAL CONTENT CARDS
  --------------------------------------------------------------------------------------*/
  .content-card,
  .trust-card,
  .cta-card {
    background: var(--white);
    border: 1px solid var(--border-color);
    border-radius: 18px;
    padding: 26px;
  }
  
  .trust-card {
    background: #fbfdff;
  }
  
  .cta-card {
    background: linear-gradient(180deg, #f8fbff 0%, #eef5ff 100%);
    border-color: #d9e7ff;
    text-align: left;
  }
  
  .cta-card h2 {
    margin-bottom: 12px;
  }
  
  .cta-card p {
    max-width: 760px;
    color: var(--text-muted);
    margin-bottom: 18px;
  }
  
  .formula-large {
    padding: 14px 16px;
    border-radius: 12px;
    background: #f8fafc;
    border: 1px solid var(--border-color);
    margin-bottom: 12px;
    font-weight: 600;
    overflow-wrap: anywhere;
  }
  
  .formula-grid {
    display: grid;
    gap: 14px;
    margin-top: 18px;
    margin-bottom: 18px;
  }
  
  .formula-grid-2 {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
  
  .formula-box {
    padding: 16px;
    border-radius: 12px;
    border: 1px solid var(--border-color);
    background: #fcfdff;
  }
  
  /*-------------------------------------------------------------------------------------
                              USE / STEPS / EXAMPLES / MISTAKES
  --------------------------------------------------------------------------------------*/
  .use-grid,
  .examples-grid,
  .mistakes-grid,
  .benefit-grid,
  .tips-grid {
    display: grid;
    gap: 18px;
  }
  
  .use-grid {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
  
  .use-card,
  .example-card,
  .mini-card,
  .benefit-card,
  .tip-card {
    border: 1px solid var(--border-color);
    border-radius: 16px;
    padding: 22px;
    background: var(--white);
  }
  
  .use-card i,
  .benefit-card i {
    font-size: 1.15rem;
    color: var(--primary-blue);
    margin-bottom: 12px;
  }
  
  .use-card h3,
  .example-card h3,
  .mini-card h3,
  .benefit-card h3,
  .tip-card h3 {
    font-size: 1.08rem;
    margin-bottom: 10px;
  }
  
  .use-card p,
  .example-card p,
  .mini-card p,
  .benefit-card p,
  .tip-card p {
    color: var(--text-muted);
    margin: 0;
  }
  
  .examples-grid {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
  
  .mistakes-grid,
  .benefit-grid,
  .tips-grid {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
  
  .steps-grid {
    display: grid;
    gap: 18px;
  }
  
  .steps-grid.six-col {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
  
  .step-card {
    border: 1px solid var(--border-color);
    border-radius: 16px;
    padding: 22px;
    background: var(--white);
  }
  
  .step-number {
    width: 34px;
    height: 34px;
    border-radius: 999px;
    display: inline-grid;
    place-items: center;
    background: #eaf2ff;
    color: var(--primary-blue);
    font-weight: 800;
    margin-bottom: 12px;
  }
  
  .step-card h3 {
    font-size: 1.05rem;
    margin-bottom: 10px;
  }
  
  .step-card p {
    color: var(--text-muted);
    margin: 0;
  }
  
  /*-------------------------------------------------------------------------------------
                                          FAQ
  --------------------------------------------------------------------------------------*/
  .faq-list {
    display: grid;
    gap: 14px;
  }
  
  .faq-item {
    border: 1px solid var(--border-color);
    border-radius: 14px;
    background: var(--white);
    padding: 0 18px;
  }
  
  .faq-item summary {
    cursor: pointer;
    list-style: none;
    font-weight: 700;
    padding: 18px 0;
    position: relative;
    padding-right: 28px;
  }
  
  .faq-item summary::-webkit-details-marker {
    display: none;
  }
  
  .faq-item summary::after {
    content: "+";
    position: absolute;
    right: 0;
    top: 18px;
    font-size: 1.2rem;
    line-height: 1;
    color: var(--primary-blue);
  }
  
  .faq-item[open] summary::after {
    content: "−";
  }
  
  .faq-item p {
    color: var(--text-muted);
    padding-bottom: 18px;
    margin: 0;
  }
  
  /*-------------------------------------------------------------------------------------
                                      RELATED
  --------------------------------------------------------------------------------------*/
  .related-grid {
    display: grid;
    gap: 16px;
  }
  
  .related-grid-4 {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
  
  .related-card {
    display: block;
    padding: 20px;
    border-radius: 16px;
    border: 1px solid var(--border-color);
    background: var(--white);
    transition: var(--transition);
  }
  
  .related-card:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-sm);
  }
  
  .related-card h3 {
    font-size: 1.02rem;
    margin-bottom: 8px;
    color: var(--text-main);
  }
  
  .related-card p {
    margin: 0;
    color: var(--text-muted);
  }
  
  /*-------------------------------------------------------------------------------------
                                      RESPONSIVE
  --------------------------------------------------------------------------------------*/
  @media (max-width: 1100px) {
    .calculator-grid,
    .use-grid,
    .examples-grid,
    .mistakes-grid,
    .benefit-grid,
    .tips-grid,
    .related-grid-4,
    .steps-grid.six-col {
      grid-template-columns: repeat(2, minmax(0, 1fr));
    }
  
    .bar-row {
      grid-template-columns: 100px 1fr auto;
    }
  }
  
  @media (max-width: 768px) {
    .section-padding {
      padding: 56px 0;
    }
  
    .hero {
      padding: 20px 0 20px;
    }
  
    .form-grid,
    .results-summary-grid,
    .formula-grid-2,
    .calculator-grid,
    .use-grid,
    .examples-grid,
    .mistakes-grid,
    .benefit-grid,
    .tips-grid,
    .related-grid-4,
    .steps-grid.six-col {
      grid-template-columns: 1fr;
    }
  
    .calculator-card,
    .content-card,
    .trust-card,
    .cta-card {
      padding: 20px;
    }
  
    .button-row,
    .hero-actions {
      flex-direction: column;
      align-items: stretch;
    }
  
    .bar-row {
      grid-template-columns: 1fr;
      gap: 8px;
    }
  
    .bar-row strong {
      text-align: left;
    }
  
    .snapshot-row {
      flex-direction: column;
      align-items: flex-start;
      gap: 4px;
    }
  
    .snapshot-row strong {
      text-align: left;
    }
  }