: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
  -------------------------------------------------*/
  body {
    font-family: 'Inter', sans-serif;
    color: var(--text-main);
    background: var(--white);
    line-height: 1.7;
  }
  
  .container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 16px;
  }
  
  .section-padding {
    padding: 4.5rem 0;
  }
  
  .bg-light {
    background: var(--bg-light);
  }
  
  .left-align {
    text-align: left;
  }
  
  .section-header {
    max-width: 860px;
    margin-bottom: 2rem;
  }
  
  .section-header h2 {
    font-size: clamp(1.9rem, 3vw, 2.5rem);
    line-height: 1.2;
    margin-bottom: 0.8rem;
    color: var(--text-main);
  }
  
  .section-header p {
    color: var(--text-muted);
    font-size: 1.02rem;
  }
  
  .prose {
    max-width: 860px;
  }
  
  .prose p + p {
    margin-top: 1rem;
  }
  
  .prose a {
    color: var(--primary-blue);
    text-decoration: none;
    font-weight: 600;
  }
  
  .prose a:hover {
    text-decoration: underline;
  }
  
  .top-spacer {
    margin-top: 1.5rem;
  }
  
  /*-------------------------------------------------
                      HERO
  -------------------------------------------------*/
  .hero {
    background: var(--hero-gradient);
    color: var(--white);
    padding: 40px 0 40px;
  }
  
  .hero-content {
    display: flex;
    flex-direction: column;
    gap: 1.4rem;
  }
  
  .breadcrumb {
    display: flex;
    flex-wrap: wrap;
    gap: 0.45rem;
    font-size: 0.92rem;
    opacity: 0.92;
  }
  
  .breadcrumb a {
    color: rgba(255, 255, 255, 0.92);
    text-decoration: none;
  }
  
  .breadcrumb a:hover {
    text-decoration: underline;
  }
  
  .hero-text {
    max-width: 860px;
  }
  
  .hero h1 {
    font-size: clamp(2.1rem, 4vw, 3.6rem);
    line-height: 1.08;
    margin-bottom: 1rem;
    color: var(--white);
  }
  
  /*-------------------------------------------------
                      BUTTONS
  -------------------------------------------------*/
  .btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-height: 48px;
    padding: 0.85rem 1.35rem;
    border-radius: 12px;
    text-decoration: none;
    font-weight: 700;
    transition: var(--transition);
    border: 1px solid white;
    cursor: pointer;
  }
  
  .btn:hover {
    transform: translateY(-1px);
  }
  
  .btn-primary {
    background: var(--primary-blue);
    color: var(--white);
    box-shadow: var(--shadow-sm);
  }
  
  .btn-primary:hover {
    box-shadow: var(--shadow-md);
  }
  
  .btn-secondary {
    background: rgba(255, 255, 255, 0.14);
    color: var(--white);
    border-color: rgba(255, 255, 255, 0.26);
  }
  
  .btn-secondary:hover {
    background: rgba(255, 255, 255, 0.2);
  }
  
  .btn-light {
    background: var(--white);
    color: var(--text-main);
    border: 1px solid var(--border-color);
  }
  
  /*-------------------------------------------------
                  CALCULATOR AREA
  -------------------------------------------------*/
  .calculator-grid {
    display: grid;
    grid-template-columns: minmax(0, 1.2fr) minmax(320px, 0.8fr);
    gap: 1.5rem;
    align-items: start;
  }
  
  .calculator-card {
    background: var(--white);
    border: 1px solid var(--border-color);
    border-radius: 18px;
    box-shadow: var(--shadow-sm);
    padding: 1.7rem;
  }
  
  .calculator-card h3 {
    font-size: 1.35rem;
    margin-bottom: 0.55rem;
  }
  
  .card-intro {
    color: var(--text-muted);
    margin-bottom: 1.3rem;
  }
  
  .form-grid {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 1rem 1rem;
  }
  
  .form-group {
    display: flex;
    flex-direction: column;
  }
  
  .form-group label {
    font-weight: 600;
    margin-bottom: 0.45rem;
    color: var(--text-main);
  }
  
  .form-group input,
  .form-group select {
    width: 100%;
    min-height: 48px;
    padding: 0.85rem 0.95rem;
    border-radius: 12px;
    border: 1px solid var(--border-color);
    background: var(--white);
    color: var(--text-main);
    font: inherit;
    transition: var(--transition);
  }
  
  .form-group input:focus,
  .form-group select:focus {
    outline: none;
    border-color: var(--primary-blue);
    box-shadow: 0 0 0 4px rgba(0, 82, 204, 0.08);
  }
  
  .form-group small {
    margin-top: 0.45rem;
    color: var(--text-muted);
    font-size: 0.87rem;
  }
  
  .inline-inputs {
    display: grid;
    grid-template-columns: 1fr 130px;
    gap: 0.7rem;
  }
  
  .advanced-toggle-wrap {
    margin-top: 1.25rem;
    padding: 1rem 1.05rem;
    border: 1px dashed var(--border-color);
    border-radius: 14px;
    background: var(--bg-light);
  }
  
  .toggle-row {
    display: inline-flex;
    align-items: center;
    gap: 0.65rem;
    font-weight: 600;
    cursor: pointer;
  }
  
  .toggle-row input {
    width: 18px;
    height: 18px;
    accent-color: var(--primary-blue);
  }
  
  .advanced-toggle-wrap small {
    display: block;
    margin-top: 0.45rem;
    color: var(--text-muted);
  }
  
  .button-row {
    display: flex;
    flex-wrap: wrap;
    gap: 0.85rem;
    margin-top: 1.4rem;
  }
  
  .form-message {
    margin-bottom: 1rem;
    padding: 0.9rem 1rem;
    border-radius: 12px;
    font-weight: 600;
  }
  
  .error-message {
    background: var(--danger-bg);
    color: var(--danger-text);
    border: 1px solid rgba(185, 28, 28, 0.15);
  }
  
  .hidden {
    display: none !important;
  }
  
  /*-------------------------------------------------
                  RESULTS AREA
  -------------------------------------------------*/
  .results-placeholder {
    min-height: 280px;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: flex-start;
    color: var(--text-muted);
    border: 1px dashed var(--border-color);
    border-radius: 16px;
    padding: 1.35rem;
    background: var(--bg-light);
  }
  
  .results-placeholder i {
    font-size: 2rem;
    margin-bottom: 0.85rem;
    color: var(--primary-blue);
  }
  
  .status-banner {
    border-radius: 16px;
    padding: 1rem 1.1rem;
    margin-bottom: 1.1rem;
  }
  
  .status-banner.general {
    background: var(--bg-light);
    color: var(--text-main);
  }
  
  .status-banner.success {
    background: var(--success-bg);
    color: var(--success-text);
  }
  
  .status-banner.warning {
    background: var(--warning-bg);
    color: var(--warning-text);
  }
  
  .status-banner.danger {
    background: var(--danger-bg);
    color: var(--danger-text);
  }
  
  .status-badge {
    display: inline-block;
    margin-bottom: 0.4rem;
    font-size: 0.8rem;
    font-weight: 800;
    letter-spacing: 0.06em;
    text-transform: uppercase;
  }
  
  .results-summary-grid {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 0.9rem;
    margin-bottom: 1rem;
  }
  
  .summary-item {
    padding: 1rem;
    border-radius: 14px;
    border: 1px solid var(--border-color);
    background: var(--white);
  }
  
  .summary-item .label {
    display: block;
    color: var(--text-muted);
    font-size: 0.9rem;
    margin-bottom: 0.45rem;
  }
  
  .summary-item strong {
    font-size: 1.08rem;
    line-height: 1.3;
  }
  
  .summary-item.accent {
    background: rgba(0, 82, 204, 0.04);
    border-color: rgba(0, 82, 204, 0.12);
  }
  
  .snapshot-card,
  .interpretation-card,
  .formula-summary-card,
  .warning-card {
    padding: 1.1rem;
    border-radius: 16px;
    border: 1px solid var(--border-color);
    background: var(--white);
    margin-top: 1rem;
  }
  
  .snapshot-card h4,
  .interpretation-card h4,
  .formula-summary-card h4,
  .warning-card h4 {
    margin-bottom: 0.75rem;
    font-size: 1.02rem;
  }
  
  .snapshot-row {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    gap: 1rem;
    padding: 0.65rem 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);
  }
  
  .warning-card {
    background: #fffdfa;
  }
  
  /*-------------------------------------------------
                  EDITORIAL STRUCTURE
  -------------------------------------------------*/
  .editorial-block {
    display: grid;
    grid-template-columns: minmax(0, 1.3fr) minmax(260px, 0.7fr);
    gap: 1.4rem;
    align-items: start;
  }
  
  .editorial-side {
    display: flex;
    flex-direction: column;
    gap: 1rem;
  }
  
  .insight-card {
    background: var(--white);
    border: 1px solid var(--border-color);
    border-radius: 16px;
    box-shadow: var(--shadow-sm);
    padding: 1.25rem;
  }
  
  .insight-card h3 {
    margin-bottom: 0.55rem;
    font-size: 1.05rem;
  }
  
  .content-card {
    background: var(--white);
    border: 1px solid var(--border-color);
    border-radius: 16px;
    box-shadow: var(--shadow-sm);
    padding: 1.5rem;
  }
  
  /*-------------------------------------------------
                      GRIDS
  -------------------------------------------------*/
  .method-grid,
  .examples-grid,
  .benefit-grid,
  .tips-grid {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 1rem;
  }
  
  .method-card,
  .example-card,
  .benefit-card,
  .tip-card {
    background: var(--white);
    border: 1px solid var(--border-color);
    border-radius: 16px;
    box-shadow: var(--shadow-sm);
    padding: 1.25rem;
  }
  
  .method-card h3,
  .example-card h3,
  .benefit-card h3,
  .tip-card h3 {
    font-size: 1.05rem;
    margin-bottom: 0.55rem;
  }
  
  .benefit-card i {
    color: var(--primary-blue);
    font-size: 1.2rem;
    margin-bottom: 0.8rem;
  }
  
  /*-------------------------------------------------
                      FORMULAS
  -------------------------------------------------*/
  .formula-large {
    background: rgba(0, 82, 204, 0.04);
    border: 1px solid rgba(0, 82, 204, 0.1);
    border-radius: 16px;
    padding: 1rem 1.15rem;
    font-weight: 700;
    font-size: 1.05rem;
    line-height: 1.5;
    margin-bottom: 1rem;
    overflow-x: auto;
  }
  
  .formula-secondary {
    background: var(--bg-light);
    border-color: var(--border-color);
  }
  
  .formula-grid {
    display: grid;
    gap: 0.9rem;
    margin: 1rem 0 1rem;
  }
  
  .formula-grid-2 {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
  
  .formula-box {
    padding: 1rem;
    border-radius: 14px;
    border: 1px solid var(--border-color);
    background: var(--white);
  }
  
  /*-------------------------------------------------
                      FAQ
  -------------------------------------------------*/
  .faq-list {
    display: flex;
    flex-direction: column;
    gap: 0.9rem;
  }
  
  .faq-item {
    background: var(--white);
    border: 1px solid var(--border-color);
    border-radius: 14px;
    padding: 0;
    overflow: hidden;
  }
  
  .faq-item summary {
    list-style: none;
    cursor: pointer;
    padding: 1rem 1.15rem;
    font-weight: 700;
    position: relative;
  }
  
  .faq-item summary::-webkit-details-marker {
    display: none;
  }
  
  .faq-item summary::after {
    content: '\f078';
    font-family: "Font Awesome 6 Free";
    font-weight: 900;
    position: absolute;
    right: 1rem;
    top: 1rem;
    color: var(--text-muted);
    transition: var(--transition);
  }
  
  .faq-item[open] summary::after {
    transform: rotate(180deg);
  }
  
  .faq-item p {
    padding: 0 1.15rem 1rem;
    color: var(--text-muted);
  }
  
  /*-------------------------------------------------
                  TRUST / RELATED / CTA
  -------------------------------------------------*/
  .trust-card,
  .cta-card {
    border-radius: 18px;
    padding: 2rem;
    border: 1px solid var(--border-color);
  }
  
  .trust-card {
    background: var(--white);
    box-shadow: var(--shadow-sm);
  }
  
  .cta-card {
    background: linear-gradient(180deg, rgba(0, 82, 204, 0.04) 0%, rgba(0, 82, 204, 0.07) 100%);
    text-align: left;
  }
  
  .cta-card h2,
  .trust-card h2 {
    font-size: clamp(1.7rem, 2.8vw, 2.3rem);
    line-height: 1.2;
    margin-bottom: 0.85rem;
  }
  
  .cta-card p,
  .trust-card p {
    color: var(--text-muted);
    max-width: 760px;
    margin-bottom: 1.15rem;
  }
  
  .related-grid {
    display: grid;
    gap: 1rem;
  }
  
  .related-grid-4 {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
  
  .related-card {
    display: block;
    text-decoration: none;
    color: inherit;
    background: var(--white);
    border: 1px solid var(--border-color);
    border-radius: 16px;
    box-shadow: var(--shadow-sm);
    padding: 1.2rem;
    transition: var(--transition);
  }
  
  .related-card:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
  }
  
  .related-card h3 {
    font-size: 1rem;
    margin-bottom: 0.45rem;
    color: var(--text-main);
  }
  
  .related-card p {
    color: var(--text-muted);
    font-size: 0.94rem;
  }
  
  /*-------------------------------------------------
                  RESPONSIVE
  -------------------------------------------------*/
  @media (max-width: 1100px) {
    .calculator-grid,
    .editorial-block {
      grid-template-columns: 1fr;
    }
  
    .related-grid-4 {
      grid-template-columns: repeat(2, minmax(0, 1fr));
    }
  }
  
  @media (max-width: 900px) {
    .method-grid,
    .examples-grid,
    .benefit-grid,
    .tips-grid,
    .formula-grid-2,
    .results-summary-grid,
    .form-grid {
      grid-template-columns: 1fr;
    }
  
    .section-padding {
      padding: 3.75rem 0;
    }
  }
  
  @media (max-width: 640px) {
    .hero {
      padding: 20px 0 20px;
    }
  
    .calculator-card,
    .content-card,
    .trust-card,
    .cta-card {
      padding: 1.2rem;
    }
  
    .button-row,
    .hero-actions {
      flex-direction: column;
      align-items: stretch;
    }
  
    .inline-inputs {
      grid-template-columns: 1fr;
    }
  
    .related-grid-4 {
      grid-template-columns: 1fr;
    }
  
    .snapshot-row {
      flex-direction: column;
      gap: 0.25rem;
    }
  }