/* ==========================================================================
   AI REVIEW KIT BETA — PREMIUM CORPORATE EDITORIAL DESIGN SYSTEM
   Style Inspiration: McKinsey & Stanford AI Index Report Style
   Typography: Lora (Academic Serif Display) + Inter (Clean Sans-serif Body)
   Colors: Pure White (#FFFFFF), Cobalt Blue (#0F62FE), Slate Gray (#F8FAFC)
   ========================================================================== */

/* --------------------------------------------------------------------------
   01. RESET & VARIABLES
   -------------------------------------------------------------------------- */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

:root {
  /* McKinsey & Stanford Premium Corporate Palette */
  --canvas: #FFFFFF;               /* Màu nền tạp chí in */
  --surface: #F8FAFC;              /* Slate 50 - Nền phụ xám nhẹ tinh tế */
  --surface-dark: #0A192F;         /* Navy thẳm học thuật chuyên nghiệp */
  --ink-primary: #0F172A;          /* Slate 900 - Đen mun xám đen rất đậm */
  --ink-secondary: #334155;        /* Slate 700 - Đọc nội dung mượt mà */
  --ink-muted: #64748B;            /* Slate 500 - Metadata & caption */
  --hairline: #E2E8F0;             /* Slate 200 - Viền mảnh tinh tế 1px */
  --hairline-dark: rgba(255, 255, 255, 0.12);

  /* Primary Accent: McKinsey Cobalt Blue & Accent Amber Gold */
  --primary: #0F62FE;              /* Cobalt Blue mang tính tín nhiệm cao */
  --primary-hover: #0043CE;        /* Hover đậm hơn */
  --primary-container: #EDF5FF;    /* Nền Cobalt siêu nhẹ */
  --on-primary-container: #002D9C; /* Chữ xanh đậm trên nền Cobalt nhạt */
  --accent: #D97706;               /* Amber Gold ấm áp dùng rất chắt chiu */
  --accent-container: #FEF3C7;
  --on-accent-container: #78350F;

  /* Semantic Colors */
  --yes-bg: #F0FDF4;               /* Mint siêu nhẹ */
  --yes-fg: #166534;               /* Xanh thông đậm */
  --no-bg: #F8FAFC;                /* Slate 50 */
  --no-fg: #475569;

  /* Typography Definition (Fraunces + Inter Tight Hybrid) */
  --font-display: 'Fraunces', Georgia, serif;
  --font-sans: 'Inter Tight', system-ui, -apple-system, sans-serif;
  --font-mono: 'JetBrains Mono', monospace;

  /* Premium Fluid Typography Scale (Strictly Grid-Aligned) */
  --font-size-xs: clamp(12px, 1.4vw, 13px);     
  --font-size-sm: clamp(14px, 1.6vw, 15px);       
  --font-size-base: clamp(15px, 1.8vw, 16px);   
  --font-size-md: clamp(17px, 2vw, 18px);     
  --font-size-lg: clamp(19px, 2.2vw, 21px);       
  --font-size-xl: clamp(24px, 2.8vw, 28px);     
  --font-size-xxl: clamp(32px, 4vw, 40px);    

  /* Spacing Scale (Academic Spacing) */
  --space-xs: 4px;
  --space-sm: 8px;
  --space-md: 16px;
  --space-lg: 24px;
  --space-xl: 32px;
  --space-2xl: 48px;
  --space-3xl: 64px;
  --space-section: clamp(60px, 8vw, 100px); /* Đảm bảo spacing dọc trên mobile luôn ít nhất 60px */

  /* Layout Boundaries */
  --container-max: 1100px; /* Thon gọn học thuật */
  --gutter: 40px;
  --margin-desktop: clamp(24px, 6vw, 64px);
}

/* --------------------------------------------------------------------------
   02. BASE HTML STYLE
   -------------------------------------------------------------------------- */
html {
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
  scroll-padding-top: 80px;
}

body {
  background-color: var(--canvas);
  color: var(--ink-secondary);
  font-family: var(--font-sans);
  font-size: var(--font-size-base);
  line-height: 1.7; /* Dòng thoáng đãng cho bài viết học thuật */
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
}

/* Icons */
.material-symbols-outlined {
  font-variation-settings: 'FILL' 0, 'wght' 400, 'GRAD' 0, 'opsz' 24;
  display: inline-block;
  vertical-align: middle;
}

/* Academic Typography System */
h1, h2, h3, h4 {
  color: var(--ink-primary);
  font-family: var(--font-display);
  font-weight: 600;
  line-height: 1.25;
  letter-spacing: -0.01em;
  text-wrap: balance; /* Prevent single word wrapping on mobile */
}

h1 em, h2 em {
  font-style: italic;
  font-family: var(--font-display);
  color: var(--primary);
  font-weight: 500;
}

p {
  margin-bottom: var(--space-md);
}

a {
  color: inherit;
  text-decoration: none;
  transition: all 0.2s cubic-bezier(0.16, 1, 0.3, 1);
}

/* --------------------------------------------------------------------------
   03. LAYOUT CONTAINER & SECTIONS
   -------------------------------------------------------------------------- */
.wrap {
  width: 100%;
  max-width: var(--container-max);
  margin-left: auto;
  margin-right: auto;
  padding-left: var(--margin-desktop);
  padding-right: var(--margin-desktop);
}

/* Section spacing with fluid clamp to avoid overlap */
section {
  padding: var(--space-section) 0;
  border-bottom: 1px solid var(--hairline);
}

/* Section Header styling */
.section-num {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: var(--font-size-xs);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--primary);
  margin-bottom: var(--space-sm);
}

.section-desc {
  font-size: var(--font-size-md);
  color: var(--ink-muted);
  max-width: 640px;
  margin-top: var(--space-xs);
  font-weight: 400;
}

.section-header-center {
  text-align: center;
  display: flex;
  flex-direction: column;
  align-items: center;
  margin-bottom: var(--space-2xl);
}

.section-header-center h2 {
  font-size: var(--font-size-xl);
}

/* --------------------------------------------------------------------------
   04. BUTTONS & ACTIONS (Flat Premium)
   -------------------------------------------------------------------------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font-sans);
  font-weight: 500;
  text-align: center;
  white-space: nowrap;
  border-radius: 4px; /* Góc bo cực nhỏ kiến trúc */
  transition: all 0.2s cubic-bezier(0.16, 1, 0.3, 1);
  cursor: pointer;
  border: none;
}

.btn-primary {
  background-color: var(--primary);
  color: #FFFFFF;
}

.btn-primary:hover {
  background-color: var(--primary-hover);
  transform: translateY(-1px);
}

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

.btn-lg {
  padding: 14px 28px;
  font-size: var(--font-size-sm);
}

/* --------------------------------------------------------------------------
   05. SITE HEADER (Flat Sticky Nav)
   -------------------------------------------------------------------------- */
.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  background-color: rgba(255, 255, 255, 0.85);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--hairline);
  height: 64px;
  display: flex;
  align-items: center;
}

.header-inner {
  width: 100%;
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--margin-desktop);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.brand {
  font-family: var(--font-sans);
  font-size: var(--font-size-md);
  font-weight: 700;
  letter-spacing: -0.01em;
  color: var(--ink-primary);
}

.brand em {
  font-family: var(--font-sans);
  font-style: normal;
  color: var(--primary);
  font-weight: 500;
  font-size: 80%;
  text-transform: uppercase;
}

.nav-links {
  display: flex;
  gap: var(--space-xl);
}

.nav-link {
  font-size: var(--font-size-sm);
  font-weight: 500;
  color: var(--ink-secondary);
}

.nav-link:hover {
  color: var(--primary);
}

.nav-cta {
  background-color: var(--ink-primary);
  color: #FFFFFF;
  padding: 6px 14px;
  border-radius: 4px;
  font-size: var(--font-size-xs);
  font-weight: 500;
}

.nav-cta:hover {
  background-color: var(--primary);
}

/* --------------------------------------------------------------------------
   06. FLOATING BAR
   -------------------------------------------------------------------------- */
.float-bar {
  position: fixed;
  bottom: 24px;
  left: 50%;
  transform: translate(-50%, 150px);
  z-index: 90;
  background: var(--surface-dark);
  border: 1px solid var(--hairline-dark);
  padding: 10px 20px;
  border-radius: 6px; /* Bo nhỏ trang trọng */
  transition: transform 0.4s cubic-bezier(0.16, 1, 0.3, 1);
  max-width: 90%;
  width: 440px;
}

.float-bar.on {
  transform: translate(-50%, 0);
}

.float-inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: var(--space-md);
}

.float-text {
  font-size: var(--font-size-xs);
  font-family: var(--font-mono);
  color: #FFFFFF;
}

.float-btn {
  background-color: var(--primary);
  color: #FFFFFF;
  padding: 6px 14px;
  border-radius: 4px;
  font-size: var(--font-size-xs);
  font-weight: 500;
}

.float-btn:hover {
  background-color: var(--primary-hover);
}

/* --------------------------------------------------------------------------
   07. HERO SECTION (Editorial Typography Focus)
   -------------------------------------------------------------------------- */
.hero-section {
  padding-top: 120px;
  padding-bottom: var(--space-3xl);
  overflow: hidden;
  border-bottom: 1px solid var(--hairline);
}

.hero-grid {
  display: grid;
  grid-template-columns: 1.15fr 0.85fr;
  gap: var(--gutter);
  align-items: center;
}

.hero-content {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
}

.eyebrows-wrap {
  display: flex;
  gap: var(--space-sm);
  margin-bottom: var(--space-md);
  flex-wrap: wrap;
}

.eyebrow {
  display: inline-flex;
  align-items: center;
  background-color: var(--primary-container);
  color: var(--on-primary-container);
  padding: 4px 10px;
  border-radius: 2px;
  font-family: var(--font-mono);
  font-size: var(--font-size-xs);
  font-weight: 500;
}

.eyebrow .dot {
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background-color: var(--primary);
  display: inline-block;
  margin-right: 6px;
}

.eyebrow-secondary {
  background-color: var(--surface);
  color: var(--ink-secondary);
  border: 1px solid var(--hairline);
}

.hero-content h1 {
  font-size: var(--font-size-xxl);
  color: var(--ink-primary);
  line-height: 1.2;
  margin-bottom: var(--space-md);
}

.lede {
  font-size: var(--font-size-md);
  color: var(--ink-secondary);
  line-height: 1.6;
  margin-bottom: var(--space-xl);
  max-width: 540px;
}

.hero-actions {
  display: flex;
  flex-direction: column;
  gap: var(--space-xs);
  width: 100%;
}

.hero-note {
  font-family: var(--font-mono);
  font-size: var(--font-size-xs);
  color: var(--ink-muted);
}

/* Hero Figure & Caption */
.hero-visual {
  display: flex;
  justify-content: center;
  align-items: center;
  width: 100%;
}

.editorial-figure {
  width: 100%;
  max-width: 420px;
  display: flex;
  flex-direction: column;
  align-items: center;
}

.hero-img {
  width: 100%;
  height: auto;
  object-fit: contain;
  border: none; /* Bỏ viền hairline cứng thô */
  padding: 0;   /* Cho ảnh tràn phẳng */
  background-color: transparent;
  filter: drop-shadow(0 12px 24px rgba(0, 0, 0, 0.04)); /* Đổ bóng mịn màng */
}

.figure-caption {
  font-family: var(--font-sans);
  font-size: var(--font-size-xs);
  color: var(--ink-muted);
  margin-top: var(--space-sm);
  text-align: center;
  font-style: italic;
}

/* --------------------------------------------------------------------------
   08. PROBLEM SECTION (Editorial Quote)
   -------------------------------------------------------------------------- */
.problem-section {
  background-color: var(--surface);
}

.problem-grid {
  display: grid;
  grid-template-columns: 1.1fr 0.9fr;
  gap: var(--space-3xl);
  align-items: start;
}

.problem-content h2 {
  font-size: var(--font-size-xl);
  margin-bottom: var(--space-lg);
}

.problem-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: var(--space-lg);
  margin-bottom: var(--space-xl);
}

.problem-list li {
  display: flex;
  gap: var(--space-md);
  align-items: start;
}

.problem-list .material-symbols-outlined {
  font-size: 22px;
  color: var(--accent);
  flex-shrink: 0;
  margin-top: 2px;
}

.problem-list p {
  font-size: var(--font-size-base);
  color: var(--ink-secondary);
  line-height: 1.6;
}

.stats-box {
  display: flex;
  gap: var(--space-md);
  align-items: center;
  background-color: var(--canvas);
  padding: var(--space-md) var(--space-lg);
  border: 1px solid var(--hairline);
  border-left: 3px solid var(--primary);
}

.stat-num {
  font-family: var(--font-mono);
  font-size: var(--font-size-xl);
  font-weight: 700;
  color: var(--ink-primary);
  line-height: 1;
}

.stat-desc {
  font-size: var(--font-size-xs);
  color: var(--ink-secondary);
  line-height: 1.5;
}

/* Editorial Blockquote Sidebar */
.problem-sidebar {
  display: flex;
  flex-direction: column;
  justify-content: center;
  height: 100%;
}

.editorial-quote {
  border-left: 2px solid var(--primary);
  padding: var(--space-sm) 0 var(--space-sm) var(--space-lg);
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
}

.quote-eyebrow {
  font-family: var(--font-mono);
  font-size: var(--font-size-xs);
  font-weight: 600;
  letter-spacing: 0.05em;
  color: var(--primary);
}

.quote-text {
  font-family: var(--font-display);
  font-size: var(--font-size-md);
  line-height: 1.6;
  color: var(--ink-primary);
  font-style: italic;
}

.quote-text strong {
  font-weight: 600;
  color: var(--primary);
}

.quote-footer {
  display: flex;
  flex-direction: column;
}

.quote-author {
  font-family: var(--font-sans);
  font-weight: 600;
  font-size: var(--font-size-sm);
  color: var(--ink-primary);
}

.quote-title {
  font-family: var(--font-sans);
  font-size: var(--font-size-xs);
  color: var(--ink-muted);
}

/* --------------------------------------------------------------------------
   09. FRAMEWORK SECTION (Minimal Data Bento Grid)
   -------------------------------------------------------------------------- */
.fw-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 20px;
  margin-top: var(--space-2xl);
}

.fw-card {
  background-color: var(--canvas);
  border: 1px solid var(--hairline);
  padding: 24px;
  border-radius: 4px; /* Phẳng hơn, chuyên nghiệp */
  display: flex;
  flex-direction: column;
  align-items: start;
  gap: var(--space-sm);
  transition: all 0.2s cubic-bezier(0.16, 1, 0.3, 1);
  position: relative;
}

.fw-card:hover {
  border-color: var(--primary);
  background-color: var(--surface);
}

.fw-icon {
  width: 40px;
  height: 40px;
  background-color: var(--surface);
  color: var(--ink-primary);
  display: flex;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--hairline);
  margin-bottom: var(--space-xs);
}

.fw-icon .material-symbols-outlined {
  font-size: 20px;
}

.fw-num {
  position: absolute;
  top: 24px;
  right: 24px;
  font-family: var(--font-mono);
  font-size: var(--font-size-xs);
  font-weight: 500;
  color: var(--ink-muted);
}

.fw-name {
  font-family: var(--font-sans);
  font-size: var(--font-size-md);
  font-weight: 700;
  color: var(--ink-primary);
}

.fw-vn {
  font-family: var(--font-sans);
  font-size: var(--font-size-xs);
  color: var(--ink-muted);
  font-weight: 600;
  margin-top: -6px;
  text-transform: uppercase;
}

.fw-desc {
  font-size: var(--font-size-xs);
  color: var(--ink-secondary);
  line-height: 1.6;
}

.fw-review {
  margin-top: auto;
  padding-top: var(--space-md);
  font-size: var(--font-size-xs);
  font-style: italic;
  font-weight: 500;
  color: var(--primary);
  border-top: 1px solid var(--hairline);
  width: 100%;
}

/* Card Đặc biệt Lớp 4 (Judgement) */
.fw-card--special {
  background-color: var(--primary-container);
  border: 1px solid var(--primary);
}

.fw-card--special .fw-icon {
  background-color: var(--canvas);
  color: var(--primary);
}

.fw-card--special .fw-name {
  color: var(--on-primary-container);
}

.fw-card--special .fw-vn {
  color: var(--primary);
}

.fw-card--special .fw-review {
  color: var(--on-primary-container);
  border-top-color: rgba(15, 98, 254, 0.15);
}

/* --------------------------------------------------------------------------
   10. DELIVERABLES SECTION (Timeline & Structured Deliverables)
   -------------------------------------------------------------------------- */
.deliverables-section {
  background-color: var(--surface);
}

.deliverables-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-3xl);
  margin-top: var(--space-2xl);
}

.tl {
  position: relative;
  padding-left: var(--space-lg);
  margin-top: var(--space-lg);
}

.tl::before {
  content: "";
  position: absolute;
  top: 10px;
  bottom: 10px;
  left: 20px;
  width: 1px;
  background-color: var(--hairline);
}

.tl-item {
  position: relative;
  padding-left: var(--space-xl);
  margin-bottom: var(--space-xl);
}

.tl-item:last-child {
  margin-bottom: 0;
}

.tl-day {
  position: absolute;
  left: -28px;
  top: 4px;
  background-color: var(--canvas);
  color: var(--ink-primary);
  font-family: var(--font-mono);
  font-size: 10px;
  font-weight: 600;
  padding: 2px 6px;
  border: 1px solid var(--hairline);
  z-index: 2;
  text-transform: uppercase;
}

.tl-item:nth-child(even) .tl-day {
  border-color: var(--primary);
  color: var(--primary);
}

.tl-title {
  font-family: var(--font-sans);
  font-size: var(--font-size-sm);
  font-weight: 700;
  color: var(--ink-primary);
}

.tl-sub {
  font-size: var(--font-size-xs);
  color: var(--ink-muted);
  margin-top: 2px;
}

/* Side Deliverable list */
.dels-box {
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
}

.del-card {
  background-color: var(--canvas);
  border: 1px solid var(--hairline);
  padding: 16px var(--space-lg);
  border-radius: 4px;
  display: flex;
  gap: var(--space-md);
  align-items: start;
}

.del-icon {
  width: 36px;
  height: 36px;
  background-color: var(--surface);
  color: var(--primary);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  border: 1px solid var(--hairline);
}

.del-icon .material-symbols-outlined {
  font-size: 18px;
}

.del-text strong {
  font-family: var(--font-sans);
  font-size: var(--font-size-sm);
  font-weight: 700;
  color: var(--ink-primary);
  display: block;
  margin-bottom: 2px;
}

.del-text p {
  font-size: var(--font-size-xs);
  color: var(--ink-secondary);
  line-height: 1.5;
}

/* --------------------------------------------------------------------------
   11. FIT SECTION (Comparison Layout)
   -------------------------------------------------------------------------- */
.fit-pair {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--gutter);
  margin-top: var(--space-2xl);
}

.fit-col {
  padding: 32px;
  border-radius: 4px;
  border: 1px solid var(--hairline);
  background-color: var(--surface);
  display: flex;
  flex-direction: column;
  gap: var(--space-lg);
}

.fit-col--yes {
  background-color: var(--yes-bg);
  border-color: rgba(22, 101, 52, 0.15);
}

.fit-col--no {
  background-color: var(--canvas);
}

.fit-h {
  display: flex;
  gap: var(--space-sm);
  align-items: center;
}

.fit-h h3 {
  font-size: var(--font-size-md);
}

.fit-col--yes .fit-h h3 {
  color: var(--yes-fg);
}

.fit-col--yes .material-symbols-outlined {
  color: var(--yes-fg);
  font-size: 24px;
}

.fit-col--no .fit-h h3 {
  color: var(--ink-primary);
}

.fit-col--no .material-symbols-outlined {
  color: var(--ink-muted);
  font-size: 24px;
}

.fit-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
}

.fit-list li {
  font-size: var(--font-size-sm);
  position: relative;
  padding-left: 20px;
  line-height: 1.6;
}

.fit-col--yes .fit-list li {
  color: var(--yes-fg);
}

.fit-col--yes .fit-list li::before {
  content: "→";
  position: absolute;
  left: 0;
  color: var(--yes-fg);
}

.fit-col--no .fit-list li {
  color: var(--ink-secondary);
}

.fit-col--no .fit-list li::before {
  content: "•";
  position: absolute;
  left: 0;
  color: var(--ink-muted);
}

/* --------------------------------------------------------------------------
   12. AUTHOR SECTION (Editorial Scholar Bio)
   -------------------------------------------------------------------------- */
.author-section-editorial {
  background-color: var(--surface);
}

.author-grid {
  display: grid;
  grid-template-columns: 0.85fr 1.15fr;
  gap: var(--space-3xl);
  align-items: center;
}

.author-visual {
  display: flex;
  justify-content: center;
}

.avatar-frame {
  position: relative;
  width: 280px;
  height: 280px;
  border: none;
  padding: 0;
  background-color: transparent;
  border-radius: 50%; /* Tròn mềm mại giống McKinsey */
  overflow: hidden;
  box-shadow: 0 12px 24px rgba(0, 0, 0, 0.05);
  border: 2px solid var(--canvas);
}

.author-img-large {
  width: 100%;
  height: 100%;
  object-fit: cover;
  border: none;
}

.experience-badge {
  position: absolute;
  bottom: -15px;
  right: -15px;
  background-color: var(--ink-primary);
  color: #FFFFFF;
  padding: 8px 14px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--hairline-dark);
}

.exp-num {
  font-family: var(--font-mono);
  font-size: var(--font-size-xs);
  font-weight: 600;
}

.exp-desc {
  font-size: 9px;
  text-transform: uppercase;
  font-weight: 500;
  letter-spacing: 0.05em;
  opacity: 0.8;
}

.author-details h2 {
  font-size: var(--font-size-xl);
  margin-bottom: var(--space-sm);
}

.author-name {
  font-family: var(--font-sans);
  font-size: var(--font-size-md);
  font-weight: 700;
  color: var(--ink-primary);
  margin-top: var(--space-md);
}

.author-title {
  font-family: var(--font-sans);
  font-size: var(--font-size-sm);
  color: var(--primary);
  font-weight: 600;
}

.author-context {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: var(--font-size-xs);
  color: var(--ink-muted);
  margin-bottom: var(--space-md);
}

.author-bio {
  font-family: var(--font-sans);
  font-size: var(--font-size-sm);
  line-height: 1.7;
  color: var(--ink-secondary);
  margin-bottom: var(--space-xl);
}

.proofs {
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
}

.proof-item {
  display: flex;
  gap: var(--space-sm);
  align-items: start;
}

.proof-item .material-symbols-outlined {
  color: var(--primary);
  font-size: 18px;
  flex-shrink: 0;
  margin-top: 3px;
}

.proof-item p {
  font-size: var(--font-size-xs);
  color: var(--ink-secondary);
  line-height: 1.5;
}

/* --------------------------------------------------------------------------
   13. PRICING SECTION (Academic Column Pricing)
   -------------------------------------------------------------------------- */
.pricing-section {
  background-color: var(--canvas);
}

.pricing-section h2 {
  text-align: center;
  font-size: var(--font-size-xl);
  margin-bottom: var(--space-2xl);
}

.pricing-card {
  max-width: 580px;
  margin: 0 auto;
  background-color: var(--canvas);
  border: 1px solid var(--primary);
  border-radius: 4px;
  overflow: hidden;
}

.pricing-head {
  padding: 32px;
  background-color: var(--surface);
  border-bottom: 1px solid var(--hairline);
  text-align: center;
}

.pricing-chip {
  display: inline-block;
  background-color: var(--primary-container);
  color: var(--on-primary-container);
  font-family: var(--font-mono);
  font-size: var(--font-size-xs);
  font-weight: 600;
  text-transform: uppercase;
  padding: 4px 10px;
  letter-spacing: 0.05em;
  margin-bottom: var(--space-sm);
}

.pricing-amount {
  font-family: var(--font-display);
  font-size: clamp(36px, 5vw, 48px);
  font-weight: 600;
  line-height: 1;
  color: var(--ink-primary);
  margin-bottom: var(--space-xs);
}

.pricing-amount small {
  font-family: var(--font-sans);
  font-size: 40%;
  font-weight: 500;
}

.pricing-period {
  font-size: var(--font-size-xs);
  color: var(--ink-secondary);
  margin-bottom: 2px;
}

.pricing-future {
  font-size: var(--font-size-xs);
  color: var(--ink-muted);
}

.pricing-body {
  padding: 32px;
  border-bottom: 1px solid var(--hairline);
}

.pricing-body h3 {
  font-family: var(--font-sans);
  font-size: var(--font-size-sm);
  color: var(--ink-primary);
  margin-bottom: var(--space-md);
}

.pricing-body ul {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.pricing-body li {
  font-size: var(--font-size-sm);
  position: relative;
  padding-left: 20px;
  color: var(--ink-secondary);
}

.pricing-body li::before {
  content: "✓";
  position: absolute;
  left: 0;
  color: var(--primary);
  font-weight: 600;
}

.pricing-cta {
  padding: 32px;
  background-color: var(--surface);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-md);
}

.pricing-cta .btn {
  width: 100%;
  max-width: 360px;
}

/* Scarcity Bar */
.scarcity-bar {
  width: 100%;
  max-width: 360px;
  display: flex;
  flex-direction: column;
  gap: var(--space-xs);
}

.scarcity-labels {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-family: var(--font-mono);
  font-size: 10px;
}

.slots-text {
  font-weight: 600;
  color: var(--primary);
  display: flex;
  align-items: center;
  gap: 4px;
}

.slots-dot {
  width: 5px;
  height: 5px;
  border-radius: 50%;
  background-color: var(--primary);
  display: inline-block;
  animation: blink-dot 1.2s infinite;
}

.percent-text {
  color: var(--ink-muted);
}

.progress-track {
  width: 100%;
  height: 4px;
  background-color: var(--hairline);
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  background-color: var(--primary);
  transition: width 1s ease-out;
}

@keyframes blink-dot {
  0% { opacity: 0.2; }
  50% { opacity: 1; }
  100% { opacity: 0.2; }
}

.disclaimer {
  text-align: center;
  font-size: var(--font-size-xs);
  color: var(--ink-muted);
  max-width: 480px;
  margin: var(--space-lg) auto 0;
  line-height: 1.5;
}

/* --------------------------------------------------------------------------
   14. FAQ SECTION (Accordion Details)
   -------------------------------------------------------------------------- */
.faq-section {
  background-color: var(--surface);
}

.faq-list {
  max-width: 680px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.faq-item {
  border: 1px solid var(--hairline);
  background-color: var(--canvas);
  border-radius: 2px;
  overflow: hidden;
  transition: all 0.2s ease;
}

.faq-item:hover {
  background-color: var(--surface);
}

.faq-item[open] {
  background-color: var(--canvas);
  border-color: var(--primary);
}

.faq-q {
  padding: 16px 20px;
  font-family: var(--font-sans);
  font-size: var(--font-size-sm);
  font-weight: 700;
  color: var(--ink-primary);
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
  list-style: none;
}

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

.faq-arrow {
  color: var(--ink-muted);
  transition: transform 0.2s cubic-bezier(0.16, 1, 0.3, 1);
  font-size: 20px;
}

.faq-item[open] .faq-arrow {
  transform: rotate(180deg);
  color: var(--primary);
}

.faq-a {
  padding: 0 20px 16px;
  font-size: var(--font-size-xs);
  color: var(--ink-secondary);
  line-height: 1.6;
  border-top: 1px dashed transparent;
}

.faq-item[open] .faq-a {
  border-top-color: var(--hairline);
}

/* --------------------------------------------------------------------------
   15. FOOTER
   -------------------------------------------------------------------------- */
footer {
  background-color: var(--surface-dark);
  color: var(--ink-muted);
  padding: 32px 0;
}

.footer-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: var(--space-lg);
}

.footer-brand {
  font-family: var(--font-sans);
  font-size: var(--font-size-xs);
  color: #FFFFFF;
  font-weight: 600;
}

.footer-links {
  display: flex;
  gap: var(--space-lg);
}

.footer-link {
  font-size: var(--font-size-xs);
  color: var(--ink-muted);
}

.footer-link:hover {
  color: #FFFFFF;
}

.footer-ver {
  font-family: var(--font-mono);
  font-size: var(--font-size-xs);
}

/* --------------------------------------------------------------------------
   16. REVEAL ANIMATION
   -------------------------------------------------------------------------- */
.reveal {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.8s cubic-bezier(0.16, 1, 0.3, 1), transform 0.8s cubic-bezier(0.16, 1, 0.3, 1);
}

.reveal.is-in {
  opacity: 1;
  transform: translateY(0);
}

/* --------------------------------------------------------------------------
   17. 100% ROBUST RESPONSIVE DESIGN (Media Queries)
   -------------------------------------------------------------------------- */

/* TABLET breakpoint (under 1024px) */
@media (max-width: 1024px) {
  :root {
    --margin-desktop: 32px;
  }
  
  .hero-grid, .problem-grid, .author-grid {
    grid-template-columns: 1fr;
    gap: var(--space-xl);
  }
  
  .hero-content {
    align-items: center;
    text-align: center;
  }
  
  .hero-actions {
    align-items: center;
  }
  
  .hero-visual {
    margin-top: var(--space-lg);
  }

  .fw-grid {
    grid-template-columns: repeat(2, 1fr);
  }
  
  .deliverables-grid {
    grid-template-columns: 1fr;
  }
}

/* MOBILE breakpoint (under 768px) */
@media (max-width: 768px) {
  :root {
    --margin-desktop: 20px;
  }

  .nav-links {
    display: none; /* Thu gọn menu trên mobile */
  }

  .hero-section {
    padding-top: 96px;
  }

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

  .fw-icon {
    margin-bottom: var(--space-sm); /* Tăng spacing nhẹ trên mobile */
  }
  
  .fit-pair {
    grid-template-columns: 1fr;
    gap: var(--space-lg);
  }
  
  .footer-row {
    flex-direction: column;
    text-align: center;
    gap: var(--space-md);
  }
  
  .avatar-frame {
    width: 240px;
    height: 240px;
  }
  
  .experience-badge {
    bottom: -10px;
    right: -10px;
    padding: 6px 12px;
  }
}

/* MICRO DEVICE PROTECTION (under 480px) */
@media (max-width: 480px) {
  :root {
    --margin-desktop: 16px;
  }
  
  .site-header .nav-cta {
    display: none; /* Ẩn nút đăng ký mini để thoáng lề */
  }
  
  .btn-lg {
    padding: 12px 24px;
    width: 100%;
  }
  
  .float-bar {
    width: calc(100% - 32px);
    bottom: 16px;
    padding: 8px 12px;
  }
  
  .float-text {
    font-size: 11px;
  }
  
  .editorial-quote {
    padding-left: var(--space-md);
  }

  .tl {
    padding-left: var(--space-sm);
  }
  
  .tl::before {
    left: 15px;
  }
  
  .tl-item {
    padding-left: 28px;
  }

  .tl-day {
    left: -20px;
  }
  
  .fit-col {
    padding: 20px;
  }

  .pricing-head, .pricing-body, .pricing-cta {
    padding: 20px;
  }

  .scarcity-labels {
    flex-direction: column;
    align-items: flex-start;
    gap: 4px;
  }

  .faq-q {
    padding: 14px 16px;
  }
  
  .faq-a {
    padding: 0 16px 14px;
  }
}