/* 
  ========================================
  APA VIỆT NAM - CSS (DENSE & IMAGE-RICH)
  ========================================
*/

:root {
  --primary-color: #0ea5e9; 
  --primary-dark: #0284c7;
  --secondary-color: #3b82f6;
  --secondary-dark: #2563eb;
  --accent-color: #14b8a6; 
  --background-light: #f8fafc;
  --background-dark: #0f172a;
  --text-main: #1e293b;
  --text-muted: #475569;
  --text-light: #f1f5f9;
  
  --gradient-primary: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1);
  --shadow-lg: 0 10px 25px -3px rgb(0 0 0 / 0.15);
  
  --space-xs: 0.5rem;
  --space-sm: 1rem;
  --space-md: 1.5rem;
  --space-lg: 2.5rem; /* Reduced from 4rem */
  --space-xl: 4rem; /* Reduced from 8rem */
  
  --max-width: 1280px; /* Increased from 1200px */
  --header-height: 70px; /* Reduced from 80px */
  --border-radius-sm: 8px;
  --border-radius-md: 12px;
  --border-radius-lg: 20px;
  
  --font-sans: 'Inter', system-ui, sans-serif;
  --font-heading: 'Outfit', system-ui, sans-serif;
}

*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  scroll-behavior: smooth;
  scroll-padding-top: var(--header-height);
}

body {
  font-family: var(--font-sans);
  color: var(--text-main);
  background-color: var(--background-light);
  line-height: 1.7;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
}

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

a {
  text-decoration: none;
  color: inherit;
  transition: all 0.3s ease;
}

ul { list-style: none; }
button { cursor: pointer; border: none; outline: none; background: none; font-family: inherit; }

/* Typography */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-heading);
  font-weight: 700;
  line-height: 1.25;
  color: var(--background-dark);
}

h1 { font-size: clamp(2.2rem, 4vw, 3.5rem); margin-bottom: 1rem; }
h2 { font-size: clamp(1.8rem, 3.5vw, 2.5rem); margin-bottom: 0.5rem; }
.subtitle { font-size: 1.2rem; color: var(--primary-color); font-weight: 600; margin-bottom: 1.5rem; }
p { margin-bottom: 1rem; font-size: 1.05rem; color: var(--text-muted); text-align: justify; }

/* Header */
.main-header {
  position: fixed;
  top: 0; left: 0; width: 100%;
  height: var(--header-height);
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(10px);
  z-index: 1000;
  box-shadow: var(--shadow-sm);
}
.navbar {
  max-width: var(--max-width); margin: 0 auto; padding: 0 var(--space-sm);
  height: 100%; display: flex; align-items: center; justify-content: space-between;
}
.logo { height: 40px; }
.nav-menu { display: flex; gap: var(--space-md); align-items: center; }
.nav-menu a { font-weight: 600; font-size: 0.95rem; color: var(--text-main); padding: 0.5rem 0; position: relative; }
.nav-menu a::after {
  content: ''; position: absolute; bottom: 0; left: 0; width: 0%; height: 2px;
  background: var(--gradient-primary); transition: width 0.3s ease;
}
.nav-menu a:hover::after { width: 100%; }
.nav-menu a:hover { color: var(--primary-color); }

.hamburger { display: none; flex-direction: column; gap: 5px; padding: 10px; cursor: pointer; }
.hamburger .bar { width: 24px; height: 3px; background: var(--text-main); transition: 0.3s; border-radius: 2px; }

/* Hero Section */
.hero-section {
  padding-top: calc(var(--header-height) + var(--space-lg));
  padding-bottom: var(--space-lg);
  min-height: 85vh;
  display: grid;
  grid-template-columns: 1fr 1fr;
  align-items: center;
  gap: var(--space-lg);
  max-width: var(--max-width);
  margin: 0 auto;
  padding-left: var(--space-sm);
  padding-right: var(--space-sm);
}

.hero-description { font-size: 1.15rem; margin-bottom: 1.5rem; }
.contact-notice {
  background: #eff6ff; border-left: 4px solid var(--primary-color);
  padding: 1rem; border-radius: 0 var(--border-radius-sm) var(--border-radius-sm) 0;
  margin-bottom: 1.5rem; font-size: 0.95rem;
}
.contact-notice p { margin-bottom: 0; color: #1e3a8a; text-align: left; }

.contact-form {
  background: white; padding: 1.5rem; border-radius: var(--border-radius-md);
  box-shadow: var(--shadow-md); display: flex; flex-direction: column; gap: 1rem;
}
.form-grid { display: grid; grid-template-columns: 2fr 1fr; gap: 1rem; }
.contact-form input, .contact-form textarea {
  width: 100%; padding: 0.8rem 1rem; border: 1px solid #cbd5e1;
  border-radius: var(--border-radius-sm); font-family: inherit; font-size: 0.95rem;
  background: #f8fafc;
}
.contact-form input:focus, .contact-form textarea:focus {
  outline: none; border-color: var(--primary-color); box-shadow: 0 0 0 3px rgba(14,165,233,0.1);
}
.contact-link {
  background: var(--gradient-primary); color: white; border-radius: var(--border-radius-sm);
  font-weight: 700; font-size: 0.95rem; transition: transform 0.2s, box-shadow 0.2s;
  padding: 0.8rem;
}
.contact-link:hover { transform: translateY(-2px); box-shadow: var(--shadow-md); }

/* Hero Collage */
.hero-image-collage {
  position: relative;
  height: 500px;
  width: 100%;
}
.hero-image-collage img {
  position: absolute; border-radius: var(--border-radius-md); box-shadow: var(--shadow-lg);
}
.hero-image-collage .img-main {
  width: 80%; height: 350px; top: 0; right: 0; z-index: 1;
}
.hero-image-collage .img-sub-1 {
  width: 45%; height: 200px; bottom: 20px; left: 0; z-index: 2; border: 6px solid white;
}
.hero-image-collage .img-sub-2 {
  width: 40%; height: 180px; bottom: -10px; right: 10%; z-index: 3; border: 6px solid white;
}

/* Content Sections */
.content-section {
  padding: var(--space-xl) 0;
  background: white;
}
.content-section:nth-child(even) { background: var(--background-light); }

.content-container {
  max-width: var(--max-width); margin: 0 auto; padding: 0 var(--space-sm);
  display: grid; grid-template-columns: 1fr 1fr; gap: var(--space-xl); align-items: center;
}
.reverse-layout .content-container { grid-template-columns: 1fr 1fr; }
.reverse-layout .text-content { order: 2; }
.reverse-layout .image-content { order: 1; }

/* Stats Grid */
.stats-grid {
  display: grid; grid-template-columns: repeat(3, 1fr); gap: 1rem; margin-top: 1.5rem;
  border-top: 1px solid #e2e8f0; padding-top: 1.5rem;
}
.stat-item h3 { color: var(--primary-color); font-size: 2rem; margin-bottom: 0.2rem; }
.stat-item p { font-size: 0.9rem; font-weight: 600; text-align: center; margin: 0; }
.stat-item { text-align: center; }

/* Image Collage Layouts for Content */
.image-content { position: relative; width: 100%; height: 400px; }
.image-content img { position: absolute; border-radius: var(--border-radius-md); box-shadow: var(--shadow-lg); }

.collage-left .img-primary { width: 75%; height: 300px; top: 0; left: 0; z-index: 1; }
.collage-left .img-secondary { width: 55%; height: 220px; bottom: 0; right: 0; z-index: 2; border: 8px solid white; }

.collage-right .img-primary { width: 75%; height: 300px; top: 0; right: 0; z-index: 1; }
.collage-right .img-secondary { width: 55%; height: 220px; bottom: 0; left: 0; z-index: 2; border: 8px solid white; }

/* Sponsor Section */
.sponsor-section {
  background: linear-gradient(135deg, #0f172a 0%, #1e293b 100%);
  color: white; padding: var(--space-xl) 0; margin: var(--space-lg) 0;
}
.sponsor-container { max-width: var(--max-width); margin: 0 auto; padding: 0 var(--space-sm); }
.sponsor-badge {
  background: #fbbf24; color: #78350f; padding: 4px 12px; border-radius: 20px;
  font-size: 0.8rem; font-weight: 700; text-transform: uppercase; margin-bottom: 1rem; display: inline-block;
}
.sponsor-header h2 { color: white; margin-bottom: 2rem; font-size: 2rem; }
.sponsor-content { display: grid; grid-template-columns: 300px 1fr; gap: var(--space-lg); align-items: start; }
.sponsor-logo-box { background: white; padding: 2rem; border-radius: var(--border-radius-md); text-align: center; }
.sponsor-logo-box img { max-width: 100%; height: auto; }
.sponsor-text p { color: #cbd5e1; font-size: 1.05rem; }
.links-title { font-weight: 600; color: #93c5fd; margin-bottom: 0.5rem; text-align: left; }
.sponsor-links { display: flex; flex-wrap: wrap; gap: 0.5rem; }
.sponsor-links a {
  background: rgba(255,255,255,0.1); padding: 6px 12px; border-radius: 4px;
  font-size: 0.9rem; color: #e2e8f0; border: 1px solid rgba(255,255,255,0.2);
}
.sponsor-links a:hover { background: var(--primary-color); border-color: var(--primary-color); color: white; }
.sponsor-links a.highlight-link { border-color: #fb7185; color: #fecdd3; }
.sponsor-links a.highlight-link:hover { background: #e11d48; border-color: #e11d48; color: white; }

.dofollow-link-light { color: #38bdf8; font-weight: 600; text-decoration: none; border-bottom: 1px dashed #38bdf8; padding-bottom: 1px; }
.dofollow-link-light:hover { color: #fff; border-bottom-color: #fff; background: rgba(56, 189, 248, 0.1); border-radius: 2px; }

/* Partner Section */
.partner-section { padding: var(--space-xl) 0; background: white; }
.partner-container { max-width: var(--max-width); margin: 0 auto; padding: 0 var(--space-sm); }
.partner-heading { text-align: center; max-width: 800px; margin: 0 auto 3rem auto; }
.partner-heading h2 { font-size: 2.2rem; }
.partner-grid-text { display: grid; grid-template-columns: 1fr 1fr; gap: 2rem; }
.partner-item-text { background: var(--background-light); padding: 1.5rem; border-radius: var(--border-radius-sm); border-left: 3px solid var(--primary-color); }
.partner-item-text p { margin: 0; font-size: 0.95rem; line-height: 1.8; }
.dofollow-link { color: var(--primary-dark); font-weight: 600; text-decoration: none; border-bottom: 1px dashed var(--primary-color); }
.dofollow-link:hover { color: white; background: var(--primary-color); border-bottom: none; border-radius: 2px; padding: 0 4px; }

/* Footer */
.main-footer { background: #0f172a; color: #cbd5e1; padding-top: var(--space-xl); border-top: 1px solid #1e293b; }
.footer-container { max-width: var(--max-width); margin: 0 auto; padding: 0 var(--space-sm); }
.footer-grid { display: grid; grid-template-columns: 2fr 1fr 1.5fr; gap: var(--space-lg); margin-bottom: var(--space-lg); }
.footer-logo { height: 45px; margin-bottom: 1.5rem; background: white; padding: 5px; border-radius: 4px; }
.footer-desc { font-size: 0.95rem; }
.footer-grid h3 { color: white; font-size: 1.2rem; margin-bottom: 1rem; font-family: var(--font-heading); }
.footer-contact ul li { margin-bottom: 0.5rem; font-size: 0.9rem; }
.footer-links p { font-size: 0.9rem; line-height: 1.8; text-align: left; }
.footer-bottom { text-align: center; padding: 1.5rem 0; border-top: 1px solid #1e293b; font-size: 0.85rem; color: #64748b; }

/* Responsive */
@media (max-width: 1024px) {
  .hero-section { grid-template-columns: 1fr; padding-top: calc(var(--header-height) + var(--space-md)); min-height: auto; }
  .hero-image-collage { height: 400px; margin-top: 2rem; }
  .content-container, .reverse-layout .content-container { grid-template-columns: 1fr; gap: var(--space-lg); }
  .reverse-layout .text-content { order: 1; }
  .reverse-layout .image-content { order: 2; }
  .image-content { height: 350px; }
  .sponsor-content { grid-template-columns: 1fr; text-align: center; }
  .sponsor-logo-box { max-width: 300px; margin: 0 auto; }
  .links-title { text-align: center; }
  .sponsor-links { justify-content: center; }
  .partner-grid-text { grid-template-columns: 1fr; }
  .footer-grid { grid-template-columns: 1fr 1fr; gap: 2rem; }
}

@media (max-width: 768px) {
  .hamburger { display: flex; }
  .nav-menu {
    position: absolute; top: var(--header-height); left: -100%; width: 100%;
    background: white; flex-direction: column; padding: var(--space-md) 0;
    box-shadow: var(--shadow-md); transition: 0.3s;
  }
  .nav-menu.active { left: 0; }
  .form-grid { grid-template-columns: 1fr; }
  .stats-grid { grid-template-columns: 1fr; text-align: center; }
  .image-content { height: 250px; }
  .hero-image-collage { height: 300px; }
  .hero-image-collage .img-sub-1, .hero-image-collage .img-sub-2 { display: none; }
  .hero-image-collage .img-main { width: 100%; height: 100%; }
  .collage-left .img-secondary, .collage-right .img-secondary { display: none; }
  .collage-left .img-primary, .collage-right .img-primary { width: 100%; height: 100%; }
  .footer-grid { grid-template-columns: 1fr; }
}