:root {
    --max-width: 900px;
    --bg: #ffffff;
    --muted: #6b7280;
    --text: #111827;
    --primary: #0a6cf1;
    --primary-dark: #064bb0;
    --border: #e5e7eb;
    --shadow: 0 10px 30px rgba(15, 23, 42, 0.06);
    --radius: 14px;
  }
  
  /* base */
  *,
  *::before,
  *::after { box-sizing: border-box; }
  
  body {
    margin: 0;
    font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI",
      sans-serif;
    background: var(--bg);
    color: var(--text);
    line-height: 1.6;
  }
  
  img { max-width: 100%; display: block; }
  
  a { color: inherit; text-decoration: none; }
  
  .container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 1.25rem;
  }
  /* 
  /* header / nav 
  .header {
    position: sticky;
    top: 0;
    z-index: 20;
    background: rgba(255, 255, 255, 0.96);
    border-bottom: 1px solid rgba(226, 232, 240, 0.9);
    backdrop-filter: blur(10px);
  }
  
  .header__inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 64px;
  }
  
  .logo {
    font-weight: 800;
    letter-spacing: 0.08em;
    font-size: 0.95rem;
  }
  
  .nav__list {
    display: flex;
    gap: 1.1rem;
    align-items: center;
    font-size: 0.9rem;
  }
  
  .nav__toggle {
    display: none;
    border: 0;
    background: none;
    flex-direction: column;
    gap: 4px;
    cursor: pointer;
  }
  
  .nav__toggle span {
    width: 20px;
    height: 2px;
    background: var(--text);
    border-radius: 999px;
  }
  */

  /* buttons */
  .btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0.6rem 1.2rem;
    border-radius: 999px;
    border: none;
    background: var(--primary);
    color: #fff;
    font-size: 0.85rem;
    font-weight: 700;
    cursor: pointer;
    box-shadow: var(--shadow);
    transition: transform 0.15s ease, box-shadow 0.15s ease,
      background 0.15s ease;
  }
  
  .btn:hover {
    transform: translateY(-1px);
    background: var(--primary-dark);
  }
  
  .btn--outline {
    background: transparent;
    border: 1px solid var(--border);
    box-shadow: none;
    color: var(--text);
  }
  
  .btn--ghost {
    background: #fff;
    border: 1px solid rgba(148, 163, 184, 0.6);
    color: var(--primary);
    box-shadow: none;
  }
  
  .btn--primary {
    background: var(--primary);
    color: #fff;
  }
  
  /* section */
  .section {
    padding: 2.75rem 0 3.25rem;
  }
  
  .section--blog {
    background: #f9fafb;
  }
  
  /* read progress bar */
  .read-progress {
    position: fixed;
    top: 64px;
    left: 0;
    height: 3px;
    width: 0;
    background: var(--primary);
    z-index: 15;
  }
  
  /* cards */
  .card-header {
    background: #fff;
    border-radius: var(--radius);
    border: 1px solid var(--border);
    box-shadow: var(--shadow);
    margin: 0;
  }

  .card {
    background: #fff;
    border-radius: var(--radius);
    border: 1px solid var(--border);
    box-shadow: var(--shadow);
  }
  
  
  /* blog layout */
  .blog {
    max-width: 720px;
  }
  
  .blog-article {
    background: #fff;
    border-radius: 20px;
    padding: 1.75rem 1.6rem 2.4rem;
    box-shadow: var(--shadow);
    border: 1px solid var(--border);
  }
  
  .blog-hero {
    margin-bottom: 1.75rem;
  }
  
  .blog-kicker {
    font-size: 0.75rem;
    letter-spacing: 0.16em;
    text-transform: uppercase;
    color: var(--primary);
    margin: 0 0 0.4rem;
  }
  
  .blog-title {
    font-size: clamp(1.5rem, 2.3vw, 1.8rem);
    line-height: 1.15;
    margin: 0 0 0.75rem;
    text-transform: uppercase;
  }
  
  .blog-meta {
    display: flex;
    gap: 0.4rem;
    font-size: 0.8rem;
    color: var(--muted);
    margin-bottom: 1rem;
  }
  
  .blog-hero__image {
    padding: 0.9rem 0.9rem 0.75rem;
  }
  
  .blog-hero__image img {
    border-radius: 10px;
  }
  
  .blog-hero__image figcaption {
    margin-top: 0.5rem;
    font-size: 0.75rem;
    color: var(--muted);
    text-align: center;
  }
  
  /* sections */
  .blog-section {
    margin-bottom: 1.75rem;
  }
  
  .blog-section h2 {
    font-size: 1.1rem;
    margin: 0 0 0.6rem;
    text-transform: none;
  }
  
  .blog-section h3 {
    font-size: 0.98rem;
    margin: 1rem 0 0.3rem;
  }
  
  .blog-section p {
    margin: 0 0 0.75rem;
    font-size: 0.92rem;
  }
  
  .blog-highlight {
    font-weight: 600;
  }
  
  .blog-list {
    margin: 0.25rem 0 0.75rem 1.1rem;
    padding: 0;
    font-size: 0.9rem;
  }
  
  .blog-list li {
    margin-bottom: 0.35rem;
  }
  
  .blog-list--numbered {
    margin-left: 1.2rem;
  }
  
  .blog-image {
    margin-top: 1.1rem;
    padding: 0.9rem;
  }
  
  .blog-image img {
    border-radius: 10px;
  }
  
  .blog-image figcaption {
    font-size: 0.78rem;
    color: var(--muted);
    margin-top: 0.4rem;
    text-align: center;
  }
  
  /* challenges grid */
  .challenges-grid {
    padding: 0;
    overflow: hidden;
  }
  
  .ch-row {
    display: grid;
    grid-template-columns: 1.1fr 1.3fr;
    border-bottom: 1px solid var(--border);
    font-size: 0.9rem;
  }
  
  .ch-row:last-child {
    border-bottom: none;
  }
  
  .ch-row > div {
    padding: 0.75rem 0.9rem;
  }
  
  .ch-head {
    background: #f3f4f6;
    font-weight: 600;
  }
  
  /* CTA */
  .blog-cta {
    margin-top: 2rem;
    text-align: center;
    padding: 1.5rem 1.4rem 1.7rem;
  }
  
  .blog-cta h3 {
    margin: 0 0 0.4rem;
    font-size: 1rem;
  }
  
  .blog-cta p {
    margin: 0 0 1rem;
    font-size: 0.9rem;
    color: var(--muted);
  }
  
  .blog-cta__actions {
    display: flex;
    justify-content: center;
    gap: 0.7rem;
    flex-wrap: wrap;
  }
  
  /* footer */
  .footer {
    border-top: 1px solid var(--border);
    padding: 1.2rem 0;
    background: #f9fafb;
    font-size: 0.8rem;
  }
  
  .footer__inner {
    display: flex;
    justify-content: space-between;
    align-items: center;
  }
  
  /* responsive */
  @media (max-width: 800px) {
    .nav {
      position: absolute;
      top: 64px;
      left: 0;
      right: 0;
      background: #fff;
      border-bottom: 1px solid var(--border);
      display: none;
    }
  
    .nav.open {
      display: block;
    }
  
    .nav__list {
      flex-direction: column;
      align-items: flex-start;
      padding: 0.8rem 1.25rem 1.1rem;
    }
  
    .nav__toggle {
      display: flex;
    }
  
    .read-progress {
      top: 60px;
    }
  
    .blog-article {
      padding: 1.4rem 1.1rem 2rem;
    }
  
    .ch-row {
      grid-template-columns: 1fr;
    }
  
    .footer__inner {
      flex-direction: column;
      gap: 0.35rem;
      text-align: center;
    }
  }