/* ============================================================
   REVITAPROST BLOG STYLESHEET v2.0
   Magazine-Style Layout | High Readability | AI Search Optimized
   Inspired by: Uroferon.life (minimalist content-first design)
   Brand: Revitaprost (Navy #1a1a2e + Blue #2b7be4)
   ============================================================ */

/* ============================================================
   1. DESIGN TOKENS (CSS Variables)
   ============================================================ */
:root {
    /* Brand Colors */
    --brand-navy: #1a1a2e;
    --brand-navy-soft: #2d2d44;
    --brand-blue: #2b7be4;
    --brand-blue-dark: #1a5fc0;
    --brand-blue-light: #e8f0fe;
    --brand-blue-pale: #f0f7ff;
    --brand-blue-hover: #1a4fb8;

    /* Text Colors */
    --text-primary: #1a1a2e;
    --text-secondary: #334155;
    --text-body: #3d4756;
    --text-muted: #64748b;
    --text-light: #94a3b8;

    /* Background Colors */
    --bg-page: #ffffff;
    --bg-soft: #f8fafc;
    --bg-card: #ffffff;
    --bg-tint: #f1f5f9;
    --bg-blue-tint: #f0f7ff;

    /* Border Colors */
    --border-light: #e2e8f0;
    --border-soft: #eef0f4;
    --border-blue: #d4e4fc;

    /* Typography */
    --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", "Inter", Arial, sans-serif;
    --font-serif: Georgia, "Times New Roman", "Source Serif Pro", serif;

    /* Spacing */
    --space-xs: 4px;
    --space-sm: 8px;
    --space-md: 16px;
    --space-lg: 24px;
    --space-xl: 32px;
    --space-2xl: 48px;
    --space-3xl: 64px;

    /* Border Radius */
    --radius-sm: 6px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-pill: 50px;

    /* Shadows */
    --shadow-xs: 0 1px 2px rgba(15, 23, 42, 0.04);
    --shadow-sm: 0 1px 3px rgba(15, 23, 42, 0.06), 0 1px 2px rgba(15, 23, 42, 0.04);
    --shadow-md: 0 4px 16px rgba(15, 23, 42, 0.08);
    --shadow-lg: 0 12px 32px rgba(15, 23, 42, 0.1);
    --shadow-blue: 0 8px 24px rgba(43, 123, 228, 0.15);

    /* Transitions */
    --transition-fast: 0.15s ease;
    --transition-base: 0.25s ease;
    --transition-slow: 0.4s ease;

    /* Layout */
    --content-width: 760px;
    --content-wide: 820px;
    --container-width: 1200px;
}

/* ============================================================
   2. RESET & BASE
   ============================================================ */
*,
*::before,
*::after {
    box-sizing: border-box;
}

html {
    -webkit-text-size-adjust: 100%;
    -webkit-tap-highlight-color: transparent;
    scroll-behavior: smooth;
}

body.blog-body {
    margin: 0;
    padding: 0;
    background-color: var(--bg-page);
    color: var(--text-body);
    font-family: var(--font-sans);
    font-size: 17px;
    line-height: 1.75;
    font-weight: 400;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    text-rendering: optimizeLegibility;
    overflow-x: hidden;
}

img {
    max-width: 100%;
    height: auto;
    display: block;
}

a {
    color: var(--brand-blue);
    text-decoration: none;
    transition: color var(--transition-fast);
}

a:hover {
    color: var(--brand-blue-dark);
}

/* ============================================================
   3. HEADER (Đồng bộ trang chủ - Sticky)
   ============================================================ */
.blog-body .header {
    position: sticky;
    top: 0;
    z-index: 1000;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: saturate(180%) blur(12px);
    -webkit-backdrop-filter: saturate(180%) blur(12px);
    border-bottom: 1px solid var(--border-soft);
    box-shadow: var(--shadow-xs);
}

.blog-body .header-inner {
    max-width: var(--container-width);
    margin: 0 auto;
    padding: 14px 24px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: var(--space-lg);
}

.blog-body .logo {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    font-family: var(--font-sans);
    font-weight: 800;
    font-size: 17px;
    letter-spacing: 0.4px;
    color: var(--brand-navy);
    text-decoration: none;
    flex-shrink: 0;
}

.blog-body .logo:hover {
    color: var(--brand-navy);
}

.blog-body .logo-mark {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 36px;
    height: 36px;
    background: linear-gradient(135deg, var(--brand-blue) 0%, var(--brand-navy) 100%);
    color: #ffffff;
    border-radius: 10px;
    font-weight: 900;
    font-size: 19px;
    box-shadow: 0 2px 8px rgba(43, 123, 228, 0.25);
}

.blog-body .nav {
    display: flex;
    gap: 26px;
    align-items: center;
    flex: 1;
    justify-content: center;
}

.blog-body .nav a {
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 14.5px;
    font-weight: 500;
    position: relative;
    padding: 4px 0;
    transition: color var(--transition-fast);
}

.blog-body .nav a::after {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 0;
    right: 0;
    height: 2px;
    background: var(--brand-blue);
    transform: scaleX(0);
    transform-origin: left;
    transition: transform var(--transition-base);
    border-radius: 2px;
}

.blog-body .nav a:hover {
    color: var(--brand-blue);
}

.blog-body .nav a:hover::after {
    transform: scaleX(1);
}

/* Buttons */
.blog-body .btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 6px;
    padding: 11px 22px;
    border-radius: var(--radius-pill);
    font-family: var(--font-sans);
    font-weight: 700;
    font-size: 14px;
    line-height: 1;
    text-decoration: none;
    border: none;
    cursor: pointer;
    transition: all var(--transition-base);
    white-space: nowrap;
    flex-shrink: 0;
}

.blog-body .btn-primary {
    background: linear-gradient(135deg, var(--brand-blue) 0%, var(--brand-blue-dark) 100%);
    color: #ffffff !important;
    box-shadow: 0 4px 14px rgba(43, 123, 228, 0.28);
}

.blog-body .btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 22px rgba(43, 123, 228, 0.4);
    color: #ffffff !important;
    filter: brightness(1.05);
}

.blog-body .btn-primary:active {
    transform: translateY(0);
}

/* ============================================================
   4. MAIN LAYOUT
   ============================================================ */
.blog-main {
    padding: 0 20px 80px;
    background: var(--bg-page);
}

.blog-article {
    max-width: var(--content-wide);
    margin: 0 auto;
    padding: 40px 0 0;
    background: transparent;
}

/* ============================================================
   5. BREADCRUMB
   ============================================================ */
.breadcrumb {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: 8px;
    font-size: 13.5px;
    color: var(--text-muted);
    padding: 24px 0 8px;
    margin: 0;
    line-height: 1.5;
}

.breadcrumb a {
    color: var(--brand-blue);
    text-decoration: none;
    font-weight: 500;
    transition: color var(--transition-fast);
}

.breadcrumb a:hover {
    color: var(--brand-blue-dark);
    text-decoration: underline;
    text-underline-offset: 3px;
}

.breadcrumb .sep {
    color: var(--text-light);
    user-select: none;
    font-weight: 400;
}

/* ============================================================
   6. ARTICLE TYPOGRAPHY
   ============================================================ */
.blog-article h1 {
    font-family: var(--font-sans);
    font-size: clamp(1.75rem, 4vw, 2.4rem);
    font-weight: 800;
    color: var(--text-primary);
    line-height: 1.25;
    letter-spacing: -0.02em;
    margin: 20px 0 20px;
    padding: 0;
}

.blog-article h2 {
    font-family: var(--font-sans);
    font-size: clamp(1.4rem, 3vw, 1.7rem);
    font-weight: 700;
    color: var(--text-primary);
    line-height: 1.35;
    letter-spacing: -0.015em;
    margin: 56px 0 16px;
    padding: 0;
    scroll-margin-top: 90px;
    position: relative;
}

.blog-article h2::before {
    content: '';
    display: block;
    width: 44px;
    height: 3px;
    background: linear-gradient(90deg, var(--brand-blue), var(--brand-blue-light));
    border-radius: 3px;
    margin-bottom: 14px;
}

.blog-article h3 {
    font-family: var(--font-sans);
    font-size: clamp(1.15rem, 2.5vw, 1.3rem);
    font-weight: 700;
    color: var(--text-primary);
    line-height: 1.4;
    letter-spacing: -0.01em;
    margin: 36px 0 12px;
    padding: 0;
    scroll-margin-top: 90px;
}

.blog-article h4 {
    font-family: var(--font-sans);
    font-size: 1.05rem;
    font-weight: 700;
    color: var(--text-primary);
    line-height: 1.5;
    margin: 24px 0 10px;
}

.blog-article p {
    font-family: var(--font-serif);
    font-size: 18px;
    line-height: 1.85;
    color: var(--text-body);
    margin: 0 0 20px;
    letter-spacing: -0.003em;
}

.blog-article p strong {
    color: var(--text-primary);
    font-weight: 700;
}

.blog-article p em {
    font-style: italic;
    color: var(--text-secondary);
}

/* Lists */
.blog-article ul,
.blog-article ol {
    margin: 0 0 22px;
    padding-left: 0;
    list-style: none;
}

.blog-article ul li,
.blog-article ol li {
    position: relative;
    padding-left: 32px;
    font-family: var(--font-serif);
    font-size: 18px;
    line-height: 1.8;
    color: var(--text-body);
    margin-bottom: 12px;
}

.blog-article ul li::before {
    content: '';
    position: absolute;
    left: 8px;
    top: 14px;
    width: 8px;
    height: 8px;
    background: var(--brand-blue);
    border-radius: 50%;
}

.blog-article ol {
    counter-reset: item-counter;
}

.blog-article ol li {
    counter-increment: item-counter;
    padding-left: 42px;
}

.blog-article ol li::before {
    content: counter(item-counter);
    position: absolute;
    left: 0;
    top: 1px;
    width: 28px;
    height: 28px;
    background: var(--brand-blue-light);
    color: var(--brand-blue-dark);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-family: var(--font-sans);
    font-size: 13px;
    font-weight: 800;
    line-height: 1;
}

.blog-article li strong {
    color: var(--text-primary);
    font-weight: 700;
}

/* Links in content */
.blog-article p a,
.blog-article li a {
    color: var(--brand-blue);
    text-decoration: none;
    font-weight: 600;
    border-bottom: 1px solid rgba(43, 123, 228, 0.4);
    transition: all var(--transition-fast);
    padding-bottom: 1px;
}

.blog-article p a:hover,
.blog-article li a:hover {
    color: var(--brand-blue-dark);
    border-bottom-color: var(--brand-blue-dark);
    background: var(--brand-blue-pale);
}

/* Blockquote */
.blog-article blockquote {
    margin: 28px 0;
    padding: 20px 26px;
    background: var(--bg-soft);
    border-left: 4px solid var(--brand-blue);
    border-radius: 0 var(--radius-md) var(--radius-md) 0;
    font-family: var(--font-serif);
    font-size: 17px;
    font-style: italic;
    color: var(--text-secondary);
    line-height: 1.75;
}

/* Tables */
.blog-article table {
    width: 100%;
    border-collapse: collapse;
    margin: 24px 0;
    font-family: var(--font-sans);
    font-size: 15px;
    background: var(--bg-card);
    border-radius: var(--radius-md);
    overflow: hidden;
    box-shadow: var(--shadow-sm);
}

.blog-article thead {
    background: var(--brand-navy);
    color: #ffffff;
}

.blog-article thead th {
    padding: 14px 18px;
    text-align: left;
    font-weight: 700;
    font-size: 14.5px;
    letter-spacing: 0.2px;
    color: #ffffff;
}

.blog-article tbody tr {
    border-bottom: 1px solid var(--border-soft);
}

.blog-article tbody tr:nth-child(even) {
    background: var(--bg-soft);
}

.blog-article tbody td {
    padding: 14px 18px;
    color: var(--text-body);
    line-height: 1.6;
}

.blog-article tbody tr:last-child {
    border-bottom: none;
}

/* ============================================================
   7. ARTICLE META (Author, Date, Reading Time)
   ============================================================ */
.article-meta {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: 20px;
    padding: 16px 0 22px;
    margin: 0 0 28px;
    border-bottom: 1px solid var(--border-soft);
    font-family: var(--font-sans);
    font-size: 14px;
    color: var(--text-muted);
    line-height: 1.5;
}

.article-meta .meta-item {
    display: inline-flex;
    align-items: center;
    gap: 6px;
}

.article-meta a {
    color: var(--brand-blue);
    text-decoration: none;
    font-weight: 600;
    border-bottom: 1px dotted rgba(43, 123, 228, 0.4);
}

.article-meta a:hover {
    color: var(--brand-blue-dark);
    border-bottom-style: solid;
}

/* ============================================================
   8. ANSWER-FIRST BOX (Tối ưu AI Search + High Contrast)
   ============================================================ */
.answer-first {
    position: relative;
    background: var(--brand-blue-pale);
    border-left: 4px solid var(--brand-blue);
    border-radius: 0 var(--radius-md) var(--radius-md) 0;
    padding: 20px 24px 20px 26px;
    margin: 16px 0 26px;
    font-family: var(--font-sans);
    font-size: 16px;
    line-height: 1.7;
    color: var(--text-primary);
    letter-spacing: -0.005em;
}

.answer-first::before {
    content: '💡';
    position: absolute;
    top: -10px;
    left: -10px;
    width: 28px;
    height: 28px;
    background: #ffffff;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 14px;
    box-shadow: var(--shadow-sm);
    z-index: 1;
}

.answer-first strong {
    color: var(--brand-blue-dark);
    font-weight: 800;
    display: inline;
}

.answer-first p {
    font-family: var(--font-sans);
    font-size: 16px;
    line-height: 1.7;
    color: var(--text-primary);
    margin: 0;
}

/* ============================================================
   9. TABLE OF CONTENTS (TOC)
   ============================================================ */
.toc {
    background: var(--bg-soft);
    border: 1px solid var(--border-light);
    border-radius: var(--radius-md);
    padding: 24px 28px;
    margin: 28px 0 36px;
    position: relative;
}

.toc h3 {
    font-family: var(--font-sans);
    font-size: 13px;
    font-weight: 800;
    color: var(--brand-navy);
    margin: 0 0 16px;
    text-transform: uppercase;
    letter-spacing: 1px;
    display: flex;
    align-items: center;
    gap: 8px;
}

.toc h3::before {
    content: '📑';
    font-size: 16px;
}

.toc ul {
    list-style: none;
    padding: 0;
    margin: 0;
    display: grid;
    gap: 8px;
    counter-reset: toc-counter;
}

.toc li {
    counter-increment: toc-counter;
    margin: 0;
    padding: 0;
}

.toc a {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 8px 12px;
    color: var(--text-secondary);
    text-decoration: none;
    font-family: var(--font-sans);
    font-size: 15px;
    font-weight: 500;
    border-radius: var(--radius-sm);
    transition: all var(--transition-fast);
    border: none;
}

.toc a::before {
    content: counter(toc-counter, decimal-leading-zero);
    color: var(--brand-blue);
    font-weight: 800;
    font-size: 12px;
    font-variant-numeric: tabular-nums;
    min-width: 22px;
    flex-shrink: 0;
}

.toc a:hover {
    background: #ffffff;
    color: var(--brand-blue-dark);
    transform: translateX(3px);
    box-shadow: var(--shadow-xs);
}

/* ============================================================
   10. CLUSTER LINKS SECTION
   ============================================================ */
.cluster-section {
    background: linear-gradient(135deg, #f0f7ff 0%, #e8f0fe 100%);
    border: 1px solid var(--border-blue);
    border-radius: var(--radius-lg);
    padding: 32px 34px;
    margin: 48px 0 36px;
    position: relative;
    overflow: hidden;
}

.cluster-section::before {
    content: '';
    position: absolute;
    top: -50px;
    right: -50px;
    width: 160px;
    height: 160px;
    background: radial-gradient(circle, rgba(43, 123, 228, 0.08), transparent 70%);
    border-radius: 50%;
    pointer-events: none;
}

.cluster-section h3 {
    font-family: var(--font-sans);
    font-size: 1.2rem;
    font-weight: 800;
    color: var(--text-primary);
    margin: 0 0 8px;
    display: flex;
    align-items: center;
    gap: 10px;
    letter-spacing: -0.01em;
    position: relative;
    z-index: 1;
}

.cluster-section .cluster-intro {
    font-family: var(--font-sans);
    font-size: 14.5px;
    color: var(--text-muted);
    margin: 0 0 22px;
    line-height: 1.6;
    position: relative;
    z-index: 1;
}

.cluster-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 12px;
    position: relative;
    z-index: 1;
}

.cluster-card {
    display: flex;
    align-items: flex-start;
    gap: 14px;
    background: #ffffff;
    border: 1px solid var(--border-light);
    border-radius: var(--radius-md);
    padding: 16px 18px;
    text-decoration: none;
    color: inherit;
    transition: all var(--transition-base);
    box-shadow: var(--shadow-xs);
}

.cluster-card:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-md);
    border-color: var(--brand-blue);
    background: #ffffff;
}

.cluster-card .cluster-icon {
    flex-shrink: 0;
    width: 42px;
    height: 42px;
    background: var(--brand-blue-light);
    color: var(--brand-blue-dark);
    border-radius: 10px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 20px;
    line-height: 1;
    transition: all var(--transition-base);
}

.cluster-card:hover .cluster-icon {
    background: var(--brand-blue);
    color: #ffffff;
    transform: scale(1.05);
}

.cluster-card .cluster-body {
    flex: 1;
    min-width: 0;
}

.cluster-card .cluster-title {
    display: block;
    font-family: var(--font-sans);
    font-size: 14.5px;
    font-weight: 700;
    color: var(--text-primary);
    line-height: 1.4;
    margin: 0 0 4px;
    letter-spacing: -0.005em;
}

.cluster-card .cluster-desc {
    display: block;
    font-family: var(--font-sans);
    font-size: 12.5px;
    color: var(--text-muted);
    line-height: 1.5;
    margin: 0;
}

/* ============================================================
   11. CTA BOX (High Contrast Fixed)
   ============================================================ */
.cta-box {
    position: relative;
    background: linear-gradient(135deg, var(--brand-navy) 0%, var(--brand-navy-soft) 100%);
    border-radius: var(--radius-lg);
    padding: 44px 40px;
    margin: 52px 0;
    text-align: center;
    color: #ffffff;
    box-shadow: 0 20px 50px rgba(26, 26, 46, 0.25);
    overflow: hidden;
}

.cta-box::before {
    content: '';
    position: absolute;
    top: -100px;
    right: -100px;
    width: 300px;
    height: 300px;
    background: radial-gradient(circle, rgba(43, 123, 228, 0.25), transparent 70%);
    border-radius: 50%;
    pointer-events: none;
}

.cta-box::after {
    content: '';
    position: absolute;
    bottom: -80px;
    left: -80px;
    width: 240px;
    height: 240px;
    background: radial-gradient(circle, rgba(108, 92, 231, 0.15), transparent 70%);
    border-radius: 50%;
    pointer-events: none;
}

.cta-box h2 {
    position: relative;
    z-index: 1;
    font-family: var(--font-sans);
    color: #ffffff !important;
    font-size: clamp(1.3rem, 3vw, 1.6rem);
    font-weight: 800;
    line-height: 1.3;
    margin: 0 0 12px !important;
    padding: 0 !important;
    letter-spacing: -0.015em;
    border: none !important;
}

.cta-box h2::before {
    display: none !important;
}

.cta-box p {
    position: relative;
    z-index: 1;
    font-family: var(--font-sans);
    color: rgba(255, 255, 255, 0.88) !important;
    font-size: 15.5px;
    line-height: 1.7;
    margin: 0 auto 26px !important;
    max-width: 540px;
}

.cta-box .btn-primary {
    position: relative;
    z-index: 1;
    background: #ffffff !important;
    color: var(--brand-navy) !important;
    padding: 16px 40px;
    font-size: 15px;
    font-weight: 800;
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.2);
    border: 2px solid transparent;
}

.cta-box .btn-primary:hover {
    background: var(--brand-blue-light) !important;
    color: var(--brand-blue-dark) !important;
    transform: translateY(-3px);
    box-shadow: 0 12px 32px rgba(0, 0, 0, 0.28);
    filter: none;
}

/* ============================================================
   12. FAQ SECTION
   ============================================================ */
.faq-section {
    margin: 48px 0 0;
    padding: 0;
}

.faq-section > h2 {
    margin-bottom: 24px;
}

.faq-section details {
    background: var(--bg-soft);
    border: 1px solid var(--border-light);
    border-radius: var(--radius-md);
    margin-bottom: 10px;
    overflow: hidden;
    transition: all var(--transition-base);
}

.faq-section details[open] {
    background: var(--brand-blue-pale);
    border-color: var(--border-blue);
    box-shadow: var(--shadow-sm);
}

.faq-section summary {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 16px;
    padding: 18px 24px;
    font-family: var(--font-sans);
    font-size: 16px;
    font-weight: 700;
    color: var(--text-primary);
    line-height: 1.5;
    cursor: pointer;
    list-style: none;
    transition: color var(--transition-fast);
    user-select: none;
}

.faq-section summary::-webkit-details-marker {
    display: none;
}

.faq-section summary::after {
    content: '+';
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 28px;
    height: 28px;
    background: #ffffff;
    color: var(--brand-blue);
    border-radius: 50%;
    font-size: 18px;
    font-weight: 700;
    line-height: 1;
    flex-shrink: 0;
    transition: all var(--transition-base);
    box-shadow: var(--shadow-xs);
}

.faq-section details[open] summary::after {
    content: '−';
    background: var(--brand-blue);
    color: #ffffff;
    transform: rotate(180deg);
}

.faq-section summary:hover {
    color: var(--brand-blue);
}

.faq-section details p {
    padding: 0 24px 20px;
    margin: 0;
    font-family: var(--font-serif);
    font-size: 16.5px;
    line-height: 1.8;
    color: var(--text-body);
}

.faq-section details p a {
    color: var(--brand-blue);
    font-weight: 600;
    border-bottom: 1px solid rgba(43, 123, 228, 0.4);
}

/* ============================================================
   13. RELATED POSTS
   ============================================================ */
.related-posts {
    background: var(--bg-soft);
    border: 1px solid var(--border-light);
    border-radius: var(--radius-lg);
    padding: 28px 32px;
    margin: 44px 0 0;
}

.related-posts h3 {
    display: flex;
    align-items: center;
    gap: 8px;
    font-family: var(--font-sans);
    font-size: 1.1rem;
    font-weight: 800;
    color: var(--text-primary);
    margin: 0 0 18px;
    letter-spacing: -0.01em;
}

.related-posts ul {
    list-style: none;
    padding: 0;
    margin: 0;
    display: grid;
    gap: 10px;
}

.related-posts li {
    padding: 0;
    margin: 0;
}

.related-posts a {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 14px 18px;
    background: #ffffff;
    border: 1px solid var(--border-light);
    border-radius: var(--radius-md);
    color: var(--text-primary);
    font-family: var(--font-sans);
    font-size: 15px;
    font-weight: 600;
    line-height: 1.5;
    text-decoration: none;
    transition: all var(--transition-base);
    box-shadow: var(--shadow-xs);
}

.related-posts a::before {
    content: '→';
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 26px;
    height: 26px;
    background: var(--brand-blue-light);
    color: var(--brand-blue);
    border-radius: 50%;
    font-weight: 700;
    font-size: 14px;
    flex-shrink: 0;
    transition: all var(--transition-base);
}

.related-posts a:hover {
    transform: translateX(4px);
    border-color: var(--brand-blue);
    box-shadow: var(--shadow-sm);
    color: var(--brand-blue-dark);
}

.related-posts a:hover::before {
    background: var(--brand-blue);
    color: #ffffff;
}

/* ============================================================
   14. FOOTER (Đồng bộ trang chủ)
   ============================================================ */
.blog-body .footer {
    background: var(--brand-navy);
    color: rgba(255, 255, 255, 0.72);
    padding: 56px 24px 32px;
    margin-top: 0;
    font-family: var(--font-sans);
}

.blog-body .footer-inner {
    max-width: var(--container-width);
    margin: 0 auto;
    display: flex;
    flex-wrap: wrap;
    gap: 40px;
    justify-content: space-between;
    align-items: flex-start;
}

.blog-body .footer-inner > div:first-child {
    flex: 1 1 480px;
    max-width: 640px;
}

.blog-body .footer .logo {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    font-weight: 800;
    font-size: 17px;
    letter-spacing: 0.4px;
    color: #ffffff;
    margin-bottom: 14px;
}

.blog-body .footer .logo-mark {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 36px;
    height: 36px;
    background: linear-gradient(135deg, var(--brand-blue), #6c5ce7);
    color: #ffffff;
    border-radius: 10px;
    font-weight: 900;
    font-size: 19px;
}

.blog-body .footer .disclaimer {
    font-size: 13px;
    line-height: 1.75;
    color: rgba(255, 255, 255, 0.6);
    margin: 0 0 20px;
    max-width: 620px;
}

.blog-body .footer-compliance p {
    font-size: 12.5px;
    line-height: 1.75;
    color: rgba(255, 255, 255, 0.55);
    margin: 0 0 8px;
}

.blog-body .footer-compliance strong {
    color: rgba(255, 255, 255, 0.9);
    font-weight: 700;
}

.blog-body .footer-links {
    display: flex;
    flex-direction: column;
    gap: 12px;
    flex-shrink: 0;
    min-width: 200px;
}

.blog-body .footer-links a {
    color: rgba(255, 255, 255, 0.72);
    text-decoration: none;
    font-size: 14px;
    font-weight: 500;
    transition: color var(--transition-fast);
    display: inline-flex;
    align-items: center;
    gap: 6px;
}

.blog-body .footer-links a::before {
    content: '↗';
    font-size: 12px;
    opacity: 0.5;
    transition: all var(--transition-fast);
}

.blog-body .footer-links a:hover {
    color: var(--brand-blue);
}

.blog-body .footer-links a:hover::before {
    opacity: 1;
    transform: translate(2px, -2px);
}

/* ============================================================
   15. STICKY CTA (Mobile Only)
   ============================================================ */
.sticky-cta {
    display: none;
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    z-index: 999;
    background: #ffffff;
    border-top: 1px solid var(--border-light);
    padding: 12px 16px;
    box-shadow: 0 -4px 20px rgba(15, 23, 42, 0.08);
    align-items: center;
    justify-content: space-between;
    gap: 12px;
}

.sticky-cta > div {
    display: flex;
    flex-direction: column;
    gap: 2px;
    min-width: 0;
    flex: 1;
}

.sticky-cta strong {
    font-family: var(--font-sans);
    font-size: 14.5px;
    font-weight: 800;
    color: var(--brand-navy);
    line-height: 1.3;
}

.sticky-cta span {
    font-family: var(--font-sans);
    font-size: 11.5px;
    color: var(--text-muted);
    line-height: 1.3;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.sticky-cta .btn-primary {
    padding: 11px 20px;
    font-size: 13.5px;
    flex-shrink: 0;
}

/* ============================================================
   16. READING PROGRESS BAR
   ============================================================ */
.reading-progress {
    position: fixed;
    top: 0;
    left: 0;
    height: 3px;
    background: linear-gradient(90deg, var(--brand-blue), #6c5ce7);
    z-index: 1100;
    width: 0%;
    transition: width 0.1s linear;
    box-shadow: 0 0 8px rgba(43, 123, 228, 0.5);
}

/* ============================================================
   17. SCROLL TO TOP BUTTON
   ============================================================ */
.scroll-top {
    position: fixed;
    bottom: 90px;
    right: 24px;
    width: 46px;
    height: 46px;
    background: #ffffff;
    border: 1px solid var(--border-light);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    box-shadow: var(--shadow-md);
    opacity: 0;
    visibility: hidden;
    transform: translateY(10px);
    transition: all var(--transition-base);
    z-index: 998;
    color: var(--brand-navy);
    font-size: 20px;
    font-weight: 700;
}

.scroll-top.visible {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.scroll-top:hover {
    background: var(--brand-blue);
    color: #ffffff;
    border-color: var(--brand-blue);
    transform: translateY(-3px);
    box-shadow: var(--shadow-blue);
}

/* ============================================================
   18. RESPONSIVE - TABLET (≤ 900px)
   ============================================================ */
@media (max-width: 900px) {
    .blog-body .header-inner {
        padding: 12px 20px;
        gap: 12px;
    }

    .blog-body .nav {
        display: none;
    }

    .blog-body .logo {
        font-size: 15px;
    }

    .blog-body .logo-mark {
        width: 32px;
        height: 32px;
        font-size: 17px;
    }

    .blog-body .btn-primary {
        padding: 9px 16px;
        font-size: 13px;
    }

    .blog-main {
        padding: 0 20px 60px;
    }

    .blog-article {
        padding-top: 24px;
    }

    .blog-article h1 {
        margin-top: 12px;
    }

    .cluster-grid {
        grid-template-columns: 1fr;
    }

    .cluster-section {
        padding: 26px 24px;
    }

    .cta-box {
        padding: 36px 28px;
    }

    .blog-body .footer-inner {
        flex-direction: column;
        gap: 28px;
    }

    .blog-body .footer-links {
        flex-direction: row;
        flex-wrap: wrap;
        min-width: 0;
    }
}

/* ============================================================
   19. RESPONSIVE - MOBILE (≤ 640px)
   ============================================================ */
@media (max-width: 640px) {
    body.blog-body {
        font-size: 16px;
    }

    .blog-body .header-inner {
        padding: 10px 16px;
    }

    .blog-body .logo {
        font-size: 14px;
        gap: 8px;
    }

    .blog-body .logo-mark {
        width: 30px;
        height: 30px;
        font-size: 16px;
        border-radius: 8px;
    }

    .blog-body .btn-primary {
        padding: 8px 14px;
        font-size: 12.5px;
    }

    .blog-main {
        padding: 0 16px 80px;
    }

    .blog-article {
        padding-top: 16px;
    }

    .breadcrumb {
        font-size: 12.5px;
        padding: 18px 0 6px;
    }

    .blog-article h1 {
        font-size: 1.55rem;
        line-height: 1.3;
        margin: 14px 0 16px;
    }

    .blog-article h2 {
        font-size: 1.25rem;
        margin-top: 42px;
        margin-bottom: 14px;
    }

    .blog-article h2::before {
        width: 36px;
        height: 3px;
        margin-bottom: 12px;
    }

    .blog-article h3 {
        font-size: 1.1rem;
        margin-top: 30px;
    }

    .blog-article p {
        font-size: 16.5px;
        line-height: 1.8;
        margin-bottom: 18px;
    }

    .blog-article ul li,
    .blog-article ol li {
        font-size: 16.5px;
        line-height: 1.75;
        margin-bottom: 10px;
    }

    .article-meta {
        gap: 14px;
        font-size: 13px;
        padding: 14px 0 18px;
        margin-bottom: 22px;
    }

    .answer-first {
        padding: 18px 20px 18px 22px;
        font-size: 15.5px;
        margin: 14px 0 22px;
    }

    .answer-first::before {
        width: 24px;
        height: 24px;
        font-size: 12px;
        top: -8px;
        left: -8px;
    }

    .toc {
        padding: 20px 22px;
        margin: 24px 0 30px;
    }

    .toc a {
        padding: 7px 10px;
        font-size: 14.5px;
    }

    .cluster-section {
        padding: 22px 20px;
        margin: 36px 0 28px;
    }

    .cluster-section h3 {
        font-size: 1.05rem;
    }

    .cluster-card {
        padding: 14px 16px;
    }

    .cluster-card .cluster-icon {
        width: 38px;
        height: 38px;
        font-size: 18px;
    }

    .cluster-card .cluster-title {
        font-size: 14px;
    }

    .cta-box {
        padding: 32px 22px;
        margin: 40px 0;
    }

    .cta-box h2 {
        font-size: 1.2rem;
    }

    .cta-box p {
        font-size: 14.5px;
        margin-bottom: 22px !important;
    }

    .cta-box .btn-primary {
        padding: 14px 28px;
        font-size: 14px;
    }

    .faq-section {
        margin-top: 40px;
    }

    .faq-section summary {
        padding: 16px 18px;
        font-size: 15px;
    }

    .faq-section summary::after {
        width: 24px;
        height: 24px;
        font-size: 16px;
    }

    .faq-section details p {
        padding: 0 18px 18px;
        font-size: 15.5px;
    }

    .related-posts {
        padding: 22px 20px;
        margin-top: 36px;
    }

    .related-posts h3 {
        font-size: 1.05rem;
    }

    .related-posts a {
        padding: 12px 14px;
        font-size: 14.5px;
    }

    .blog-body .footer {
        padding: 40px 20px 24px;
    }

    .blog-body .footer-links {
        flex-direction: column;
        gap: 10px;
    }

    /* Sticky CTA hiển thị trên mobile */
    .sticky-cta {
        display: flex;
    }

    .scroll-top {
        bottom: 82px;
        right: 16px;
        width: 42px;
        height: 42px;
        font-size: 18px;
    }
}

/* ============================================================
   20. RESPONSIVE - SMALL MOBILE (≤ 380px)
   ============================================================ */
@media (max-width: 380px) {
    .blog-body .btn-primary {
        padding: 7px 12px;
        font-size: 12px;
    }

    .blog-article h1 {
        font-size: 1.4rem;
    }

    .blog-article h2 {
        font-size: 1.15rem;
    }

    .blog-article p,
    .blog-article ul li,
    .blog-article ol li {
        font-size: 16px;
    }

    .sticky-cta .btn-primary {
        padding: 9px 14px;
        font-size: 12px;
    }

    .sticky-cta strong {
        font-size: 13px;
    }

    .sticky-cta span {
        font-size: 10.5px;
    }
}

/* ============================================================
   21. PRINT STYLES
   ============================================================ */
@media print {
    .blog-body .header,
    .blog-body .footer,
    .sticky-cta,
    .scroll-top,
    .reading-progress,
    .cta-box,
    .related-posts,
    .cluster-section {
        display: none !important;
    }

    body.blog-body {
        background: #ffffff;
        color: #000000;
        font-size: 12pt;
    }

    .blog-article {
        max-width: 100%;
        padding: 0;
    }

    .blog-article h1,
    .blog-article h2,
    .blog-article h3 {
        color: #000000;
        page-break-after: avoid;
    }

    .blog-article a {
        color: #000000;
        text-decoration: underline;
    }

    .answer-first {
        border: 1px solid #000000;
        background: #f5f5f5;
    }
}

/* ============================================================
   22. ACCESSIBILITY & FOCUS STATES
   ============================================================ */
.blog-body a:focus-visible,
.blog-body button:focus-visible,
.blog-body summary:focus-visible {
    outline: 2px solid var(--brand-blue);
    outline-offset: 3px;
    border-radius: 4px;
}

.blog-body .btn:focus-visible {
    outline: 2px solid var(--brand-blue);
    outline-offset: 3px;
}

/* Reduced motion */
@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
        scroll-behavior: auto !important;
    }
}

/* High contrast mode */
@media (prefers-contrast: high) {
    .answer-first {
        border-left-width: 6px;
    }

    .cluster-card {
        border-width: 2px;
    }

    .blog-article p a,
    .blog-article li a {
        border-bottom-width: 2px;
    }
}

/* Dark mode support */
@media (prefers-color-scheme: dark) {
    /* Chỉ áp dụng cho thiết bị người dùng bật dark mode,
       nhưng giữ blog ở light mode để đảm bảo tính đồng bộ với trang chủ Revitaprost */
}