/* HEADER STYLES */
.header {
  background: #ffffff;
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
  padding: 15px 0;
  position: sticky;
  top: 0;
  z-index: 1000;
  border-bottom: 2px solid #2563eb;
}

.header .container {
  display: flex;
  justify-content: space-between;
  align-items: center;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 20px;
}

.logo {
  font-size: 28px;
  font-weight: 800;
  color: #2563eb;
  text-decoration: none;
  display: flex;
  align-items: center;
  gap: 8px;
  transition: all 0.3s ease;
}

.logo:hover {
  color: #1d4ed8;
  transform: translateY(-2px);
}

.logo::before {
  content: "";
  font-size: 24px;
}

/* NAVIGATION */
.nav {
  display: flex;
  gap: 30px;
  align-items: center;
  position: relative;
}

.nav a {
  text-decoration: none;
  color: #334155;
  font-weight: 600;
  padding: 10px 16px;
  border-radius: 8px;
  transition: all 0.3s ease;
  position: relative;
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 15px;
}

.nav a:hover {
  color: #2563eb;
  background: linear-gradient(135deg, #f8fafc, #e2e8f0);
  transform: translateY(-1px);
}

.nav a.active {
  color: #2563eb;
  background: linear-gradient(135deg, #dbeafe, #eff6ff);
  box-shadow: 0 2px 8px rgba(37, 99, 235, 0.2);
}

.nav a.active::after {
  content: "";
  position: absolute;
  bottom: -2px;
  left: 16px;
  right: 16px;
  height: 2px;
  background: linear-gradient(90deg, #2563eb, #1d4ed8);
  border-radius: 2px;
}

/* DROPDOWN STYLES */
.dropdown {
  position: relative;
}

.dropdown-toggle {
  display: flex;
  align-items: center;
  gap: 6px;
  cursor: pointer;
  position: relative;
}

.dropdown-toggle::after {
  content: "▼";
  font-size: 10px;
  margin-left: 4px;
  transition: transform 0.3s ease;
  color: #64748b;
}

.dropdown:hover .dropdown-toggle::after {
  transform: rotate(180deg);
  color: #2563eb;
}

.dropdown-menu {
  position: absolute;
  top: 100%;
  right: 0;
  background: #ffffff;
  min-width: 280px;
  box-shadow: 0 10px 25px rgba(0, 0, 0, 0.15);
  border-radius: 12px;
  padding: 8px;
  opacity: 0;
  visibility: hidden;
  transform: translateY(-10px);
  transition: all 0.3s ease;
  z-index: 1000;
  border: 1px solid #e2e8f0;
  margin-top: 8px;
}

.dropdown:hover .dropdown-menu {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.dropdown-menu::before {
  content: "";
  position: absolute;
  top: -6px;
  right: 20px;
  width: 12px;
  height: 12px;
  background: #ffffff;
  transform: rotate(45deg);
  border-left: 1px solid #e2e8f0;
  border-top: 1px solid #e2e8f0;
}

/* DROPDOWN ITEMS */
.dropdown-item {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 12px 16px;
  text-decoration: none;
  color: #475569;
  border-radius: 8px;
  transition: all 0.2s ease;
  font-weight: 500;
  border: 1px solid transparent;
}

.dropdown-item:hover {
  background: linear-gradient(135deg, #eff6ff, #dbeafe);
  color: #2563eb;
  border-color: #dbeafe;
  transform: translateX(4px);
}

/* SOCIAL MEDIA ICONS */
.zalo-icon {
  background: linear-gradient(135deg, #0068ff, #0099ff);
  color: white;
  width: 24px;
  height: 24px;
  border-radius: 6px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 14px;
  box-shadow: 0 2px 6px rgba(0, 104, 255, 0.3);
}

.facebook-icon {
  background: linear-gradient(135deg, #1877f2, #42b883);
  color: white;
  width: 24px;
  height: 24px;
  border-radius: 6px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 14px;
  box-shadow: 0 2px 6px rgba(24, 119, 242, 0.3);
}

/* RESPONSIVE DESIGN */
@media (max-width: 768px) {
  .header .container {
    flex-direction: column;
    gap: 15px;
    padding: 15px 20px;
  }

  .nav {
    gap: 15px;
    flex-wrap: wrap;
    justify-content: center;
  }

  .nav a {
    padding: 8px 12px;
    font-size: 14px;
  }

  .dropdown-menu {
    position: fixed;
    left: 50%;
    transform: translateX(-50%) translateY(-10px);
    min-width: 90vw;
    max-width: 90vw;
  }

  .dropdown:hover .dropdown-menu {
    transform: translateX(-50%) translateY(0);
  }

  .dropdown-menu::before {
    right: 50%;
    transform: translateX(50%) rotate(45deg);
  }
}

@media (max-width: 480px) {
  .nav {
    gap: 8px;
  }

  .nav a {
    padding: 6px 10px;
    font-size: 13px;
  }

  .logo {
    font-size: 24px;
  }
}

/* ANIMATIONS */
@keyframes slideDown {
  from {
    opacity: 0;
    transform: translateY(-10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.dropdown-menu {
  animation: slideDown 0.3s ease;
}

/* HOVER EFFECTS ENHANCEMENT */
.nav a::before {
  content: "";
  position: absolute;
  bottom: 0;
  left: 50%;
  width: 0;
  height: 2px;
  background: linear-gradient(90deg, #2563eb, #1d4ed8);
  transition: all 0.3s ease;
  transform: translateX(-50%);
}

.nav a:hover::before {
  width: calc(100% - 32px);
}

/* ACTIVE STATE INDICATOR */
.nav a.active::before {
  width: calc(100% - 32px);
}

/* DROPDOWN ITEM ANIMATIONS */
.dropdown-item {
  position: relative;
  overflow: hidden;
}

.dropdown-item::before {
  content: "";
  position: absolute;
  left: -100%;
  top: 0;
  width: 100%;
  height: 100%;
  background: linear-gradient(90deg, transparent, rgba(37, 99, 235, 0.1), transparent);
  transition: left 0.5s ease;
}

.dropdown-item:hover::before {
  left: 100%;
}