/* ============ BLOG STYLES ============ */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    line-height: 1.7;
    color: #1f2937;
    background: #f9fafb;
}

/* Navigation */
.blog-nav {
    display: flex;
    align-items: center;
    gap: 24px;
    max-width: 800px;
    margin: 0 auto;
    padding: 16px 24px;
}
.blog-logo {
    font-size: 18px;
    font-weight: 700;
    color: #1a56db;
    text-decoration: none;
    margin-right: auto;
}
.blog-nav-link {
    font-size: 14px;
    color: #4b5563;
    text-decoration: none;
    font-weight: 500;
}
.blog-nav-link:hover { color: #1a56db; }
.btn-nav-cta {
    background: #1a56db;
    color: #fff !important;
    padding: 6px 16px;
    border-radius: 6px;
}
.btn-nav-cta:hover { background: #1e40af; }

/* Article */
.blog-article {
    max-width: 720px;
    margin: 0 auto;
    padding: 0 24px;
}
.article-header {
    padding: 40px 0 24px;
    border-bottom: 1px solid #e5e7eb;
    margin-bottom: 32px;
}
.article-header h1 {
    font-size: 32px;
    font-weight: 800;
    line-height: 1.25;
    color: #111827;
    margin-bottom: 12px;
}
.article-meta {
    display: flex;
    gap: 16px;
    font-size: 14px;
    color: #6b7280;
}

/* Article body */
.article-body h2 {
    font-size: 24px;
    font-weight: 700;
    color: #111827;
    margin-top: 36px;
    margin-bottom: 12px;
}
.article-body h3 {
    font-size: 19px;
    font-weight: 600;
    color: #1f2937;
    margin-top: 28px;
    margin-bottom: 8px;
}
.article-body p {
    margin-bottom: 16px;
    color: #374151;
}
.article-body ul, .article-body ol {
    margin-bottom: 16px;
    padding-left: 24px;
}
.article-body li {
    margin-bottom: 6px;
    color: #374151;
}
.article-body strong {
    color: #111827;
}
.article-body blockquote {
    border-left: 4px solid #1a56db;
    padding: 12px 20px;
    margin: 20px 0;
    background: #eff6ff;
    border-radius: 0 8px 8px 0;
    color: #1e40af;
    font-style: italic;
}
.article-body table {
    width: 100%;
    border-collapse: collapse;
    margin: 20px 0;
    font-size: 14px;
}
.article-body th, .article-body td {
    padding: 10px 12px;
    text-align: left;
    border-bottom: 1px solid #e5e7eb;
}
.article-body th {
    background: #f3f4f6;
    font-weight: 600;
    color: #111827;
}
.article-body tr:hover {
    background: #f9fafb;
}

/* Practice problems */
.practice-problem {
    background: #fff;
    border: 1px solid #e5e7eb;
    border-radius: 10px;
    padding: 20px 24px;
    margin: 24px 0;
}
.practice-problem h3 {
    margin-top: 0;
    color: #1a56db;
}
.problem-question {
    font-weight: 500;
    color: #111827;
}
.problem-options {
    list-style: none;
    padding-left: 0;
    margin: 12px 0;
}
.problem-options li {
    padding: 6px 12px;
    border-radius: 6px;
    margin-bottom: 4px;
}
.problem-solution {
    margin-top: 12px;
    border-top: 1px solid #e5e7eb;
    padding-top: 12px;
}
.problem-solution summary {
    cursor: pointer;
    font-weight: 600;
    color: #1a56db;
    padding: 6px 0;
}
.problem-solution summary:hover {
    color: #1e40af;
}
.problem-solution p {
    margin-top: 8px;
}

/* CTA */
.article-cta {
    text-align: center;
    background: linear-gradient(135deg, #eff6ff, #e8f0fe);
    border: 2px solid #1a56db;
    border-radius: 12px;
    padding: 32px 24px;
    margin: 40px 0;
}
.article-cta h2 {
    font-size: 22px;
    color: #111827;
    margin-bottom: 8px;
}
.article-cta p {
    color: #4b5563;
    margin-bottom: 16px;
}
.btn-cta {
    display: inline-block;
    background: #1a56db;
    color: #fff;
    padding: 12px 32px;
    border-radius: 8px;
    text-decoration: none;
    font-weight: 600;
    font-size: 16px;
}
.btn-cta:hover { background: #1e40af; }

/* Footer */
.blog-footer {
    max-width: 720px;
    margin: 0 auto;
    padding: 32px 24px;
    text-align: center;
    font-size: 13px;
    color: #9ca3af;
    border-top: 1px solid #e5e7eb;
}
.blog-footer a {
    color: #6b7280;
    text-decoration: none;
}
.blog-footer a:hover { color: #1a56db; }
.blog-footer p { margin-bottom: 4px; }

/* Blog index page */
.blog-index {
    max-width: 720px;
    margin: 0 auto;
    padding: 40px 24px;
}
.blog-index h1 {
    font-size: 32px;
    font-weight: 800;
    margin-bottom: 8px;
}
.blog-index .blog-subtitle {
    color: #6b7280;
    margin-bottom: 32px;
}
.blog-card {
    display: block;
    background: #fff;
    border: 1px solid #e5e7eb;
    border-radius: 10px;
    padding: 24px;
    margin-bottom: 16px;
    text-decoration: none;
    transition: box-shadow 0.15s, border-color 0.15s;
}
.blog-card:hover {
    border-color: #1a56db;
    box-shadow: 0 4px 12px rgba(26,86,219,0.1);
}
.blog-card h2 {
    font-size: 19px;
    font-weight: 700;
    color: #111827;
    margin-bottom: 6px;
}
.blog-card p {
    font-size: 14px;
    color: #4b5563;
    margin-bottom: 8px;
}
.blog-card .card-meta {
    font-size: 13px;
    color: #9ca3af;
}

/* Responsive */
@media (max-width: 640px) {
    .article-header h1 { font-size: 24px; }
    .article-body h2 { font-size: 20px; }
    .blog-index h1 { font-size: 24px; }
    .practice-problem { padding: 16px; }
}