/* ============================================
   ENHANCED COLOR PALETTE
   Primary: #5385c1 (Blue)
   Secondary: #4a9cd6 (Light Blue)
   Accent: #2ecc71 (Green - success/growth)
   Warm: #f39c12 (Orange - energy)
   Neutral: #34495e (Dark Gray - text)
   ============================================ */

:root {
  --primary-blue: #5385c1;
  --primary-dark: #3a6a9f;
  --primary-light: #7ab0e0;
  --accent-green: #27ae60;
  --accent-orange: #f39c12;
  --text-dark: #2c3e50;
  --text-medium: #5d6d7e;
  --text-light: #95a5a6;
  --bg-light: #f8f9fa;
  --bg-gradient-1: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  --bg-gradient-2: linear-gradient(135deg, #5385c1 0%, #4a9cd6 50%, #2ecc71 100%);
}

html {
  scroll-behavior: smooth;
  font-family: 'Raleway', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
}

body {
  color: var(--text-dark);
}

/* ============================================
   HEADER - Enhanced with gradient
   ============================================ */
#header {
  background: var(--bg-gradient-2);
  box-shadow: 0 2px 20px rgba(83, 133, 193, 0.3);
}

#header .logo {
  font-weight: 600;
  font-size: 1.3em;
  text-shadow: 0 2px 4px rgba(0,0,0,0.2);
}

#nav a {
  position: relative;
  padding: 0.5em 1em;
  transition: all 0.3s ease;
}

#nav a:hover {
  color: #fff;
  text-shadow: 0 0 10px rgba(255,255,255,0.5);
}

#nav a::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 50%;
  width: 0;
  height: 2px;
  background: #fff;
  transition: all 0.3s ease;
  transform: translateX(-50%);
}

#nav a:hover::after {
  width: 80%;
}

/* ============================================
   MAIN CONTENT - Enhanced spacing
   ============================================ */
#main {
  padding: 4em 0;
}

#main .inner {
  max-width: 90em;
}

/* ============================================
   SECTION HEADERS - Gradient + Animation
   ============================================ */
header.align-center {
  text-align: center;
  margin-bottom: 3em;
  animation: fadeInDown 0.8s ease;
}

header.align-center h2 {
  font-size: 2.5em;
  font-weight: 600;
  background: var(--bg-gradient-2);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: 0.5em;
}

/* ============================================
   LANGUAGE GROUPS - Color coded
   ============================================ */
.lang-group {
  margin-bottom: 0.8em;
  padding: 0.5em;
  border-left: 3px solid var(--primary-light);
  padding-left: 1em;
  transition: all 0.3s ease;
}

.lang-group:hover {
  background: rgba(83, 133, 193, 0.05);
  border-left-color: var(--primary-blue);
}

.lang-group .vi {
  font-weight: 600;
  color: var(--primary-dark);
  font-size: 1.1em;
}

.lang-group .zh {
  color: var(--text-medium);
  margin-top: 0.3em;
}

.lang-group .en {
  color: var(--text-light);
  font-style: italic;
  font-size: 0.95em;
}

/* ============================================
   CONTENT BOXES - Enhanced styling
   ============================================ */
.box {
  background: #fff;
  border-radius: 8px;
  padding: 2em;
  margin: 2em 0;
  box-shadow: 0 5px 20px rgba(0,0,0,0.1);
  border: 1px solid rgba(83, 133, 193, 0.2);
  transition: all 0.3s ease;
}

.box:hover {
  transform: translateY(-3px);
  box-shadow: 0 8px 30px rgba(83, 133, 193, 0.25);
}

/* ============================================
   IMAGES - Enhanced with shadows
   ============================================ */
.image.fit {
  border-radius: 8px;
  overflow: hidden;
  box-shadow: 0 5px 20px rgba(0,0,0,0.15);
  margin: 2em 0;
}

.image.fit img {
  transition: transform 0.3s ease;
}

.image.fit:hover img {
  transform: scale(1.02);
}

/* ============================================
   LISTS - Styled with color accents
   ============================================ */
ul.alt li {
  padding: 0.8em 0;
  border-bottom: 1px solid rgba(83, 133, 193, 0.1);
  transition: all 0.3s ease;
}

ul.alt li:hover {
  background: rgba(83, 133, 193, 0.05);
  padding-left: 1em;
}

ul.alt li:last-child {
  border-bottom: none;
}

ul.alt li::before {
  content: '✓';
  color: var(--accent-green);
  font-weight: bold;
  margin-right: 0.5em;
}

/* ============================================
   HEADINGS - Color hierarchy
   ============================================ */
h4 {
  color: var(--primary-dark);
  font-weight: 600;
  margin-top: 1.5em;
  margin-bottom: 1em;
  font-size: 1.3em;
}

/* ============================================
   HR - Gradient styled
   ============================================ */
hr {
  border: none;
  height: 3px;
  background: var(--bg-gradient-2);
  margin: 3em 0;
  border-radius: 2px;
}

/* ============================================
   FOOTER - Enhanced
   ============================================ */
#footer {
  background: linear-gradient(135deg, var(--primary-dark) 0%, var(--primary-blue) 100%);
  padding: 3em 0;
  margin-top: 4em;
}

#footer .icons a {
  transition: all 0.3s ease;
}

#footer .icons a:hover {
  transform: scale(1.2) rotate(10deg);
}

.zalo-btn {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  padding: 10px 20px;
  background: #0068ff;
  color: #fff !important;
  border-radius: 25px;
  text-decoration: none;
  margin: 15px 0;
  transition: all 0.3s ease;
  box-shadow: 0 4px 15px rgba(0, 104, 255, 0.3);
}

.zalo-btn:hover {
  background: #0056d4;
  transform: translateY(-3px);
  box-shadow: 0 6px 20px rgba(0, 104, 255, 0.4);
}

.copyright {
  background: var(--text-dark);
  color: #fff;
  padding: 2em 0;
  text-align: center;
}

.copyright p {
  opacity: 0.9;
  line-height: 1.8;
}

/* ============================================
   ANIMATIONS
   ============================================ */
@keyframes fadeInDown {
  from {
    opacity: 0;
    transform: translateY(-20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* ============================================
   RESPONSIVE
   ============================================ */
@media screen and (max-width: 736px) {
  header.align-center h2 {
    font-size: 1.8em;
  }

  .box {
    padding: 1.5em;
  }

  ul.alt li:hover {
    padding-left: 0.5em;
  }

  #header .logo {
    font-size: 1.1em;
  }

  #nav a {
    padding: 0.3em 0.5em;
    font-size: 0.9em;
  }
}