justify-content: space-between;
  z-index: 1;
  background-color: #fff;
  width: 100%;
  height: 3.5rem;
}

.header-logo {
  display: flex;
  align-items: center;
  padding-left: 1rem;
  min-width: 30%;
}

.header-logo h1 {
  background-image: url("https://images.pexels.com/photos/6985001/pexels-photo-6985001.jpeg?auto=compress&cs=tinysrgb&dpr=3&h=750&w=1260");
  background-repeat: repeat;
  -webkit-text-fill-color: transparent;
  color: rgba(225, 225, 225, 0.01);
  -webkit-background-clip: text;
  animation: animate 15s ease-in-out infinite;
  background-clip: text;
  font-weight: 900;
  font-size: 2.25rem;
  text-align: center;
  text-transform: uppercase;
}

@keyframes animate {
  0%,
  100% {
    background-position: left top;
  }

  25% {
    background-position: right bottom;
  }

  50% {
    background-position: left bottom;
  }

  75% {
    background-position: right top;
  }
}

.header-nav-center {
  display: flex;
  flex: 1;
  align-items: center;
}

.header-nav-center ul {
  display: flex;
  justify-content: center;
  align-items: center;
  gap: 1.875rem;
  height: 100%;
}
.header-nav-center ul li {
  height: 100%;
  display: flex;
  align-items: center;
}

.header-nav-center a {
  color: #000000;
  font-weight: bold;
  font-size: 1rem;
  text-decoration: none;
}

.header-nav-center ul li:hover {
  cursor: pointer;
  border-bottom: 0.125rem solid var(--blue-);
}

.header-nav-right {
  display: flex;
  justify-content: end;
  align-items: center;
  gap: 0.625rem;
  min-width: 30%;
  padding-right: 10px;
}

.header-notification-icon,
.header-message-icon,
.header-search-icon .header-user-icon {
  width: 2.5rem;
  height: 2.5rem;
  border-radius: 50%;
  display: flex;
  justify-content: center;
  align-items: center;
}

.header-notification-icon img,
.header-message-icon img,
.header-search-icon img,
.header-user-icon img {
  width: 2rem;
  height: 2rem;
  cursor: pointer;
}
/* Search */
.header-search {
  position: relative;
  display: flex;
  align-items: center;
  height: 2.5rem;
  background-color: transparent;
  transition: all 0.4s ease;
  width: 2.5rem;
}

.header-search.active {
  border: 1px solid #ccc;
  width: 15rem;
  background-color: #fff;
  border-radius: 3rem;
  padding-left: 0.75rem;
}

.header-search-box {
  flex: 1;
  opacity: 0;
  transition: opacity 0.3s ease;
}

.header-search.active .header-search-box {
  opacity: 1;
}

.header-search-box input {
  width: 100%;
  border: none;
  outline: none;
  font-size: 0.875rem;
  color: #333;
  background: transparent;
}

.header-search-icon {
  width: 2.5rem;
  height: 2.5rem;
  border-radius: 50%;
  display: flex;
  justify-content: center;
  align-items: center;
  position: absolute;
  right: 0;
  top: 0;
  cursor: pointer;
}

.header-search-results {
  position: absolute;
  top: 110%;
  left: 0;
  width: 100%;
  background: #fff;
  border: 1px solid #ccc;
  border-radius: 8px;
  padding: 0.75rem;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
  display: none;
  z-index: 10;
}
.header-search-results h2{
  font-size: 1.1rem;
  font-weight: bold;
  color: #007bff;
  margin-bottom: 0.75rem;
}

.search-group {
  margin-bottom: 1rem;
}

.search-group h3 {
  font-size: 0.95rem;
  font-weight: bold;
  color: #333;
  margin-bottom: 0.5rem;
  border-bottom: 1px solid #eee;
  padding-bottom: 0.25rem;
}

.search-group ul {
  list-style: none;
  padding: 0;
  margin: 0;
}

.search-group li {
  padding: 0.5rem;
  font-size: 0.9rem;
  color: #333;
  border-bottom: 1px solid #eee;
  cursor: pointer;
}

.search-group li:hover {
  background-color: #f5f5f5;
}


/* chấm thông báo */
.header-notification,
.header-message {
  position: relative;
  display: inline-block;
  margin: 0 0.625rem;
  cursor: pointer;
}

.header-notification-count {
  position: absolute;
  top: 0.25rem;
  right: 0.25rem;
  width: 0.625rem;
  height: 0.625rem;
  background-color: #ff004f;
  border-radius: 50%;
  text-align: center;
  line-height: 1;
}
/* user */
.header-user-container {
  position: relative;
  display: inline-block;
}

.avatar {
  width: 50px;
  height: 50px;
  border-radius: 50%;
  cursor: pointer;
}

/* Tên người dùng hiện ngang */
.user-name-popup {
  position: absolute;
  top: 16%;
  right: 36px;
  transform: translateY(-50%) translateX(-10px);
  background-color: rgba(0, 0, 0, 0.8);
  color: var(--white-);
  padding: 6px 12px;
  border-radius: 6px;
  box-shadow: 0 2px 6px rgba(0, 0, 0, 0.15);
  font-size: 14px;
  white-space: nowrap;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.3s ease, transform 0.3s ease;
}

/* Khi user mở menu */
.header-user-container.active .user-menu,
.header-user-container.active .user-name-popup {
  opacity: 1;
  transform: translateY(0) translateX(0);
  pointer-events: auto;
}

.header-notification-container {
  position: relative;
  display: inline-block;
}

.notification-icon {
  width: 28px;
  height: 28px;
  cursor: pointer;
}

/* Khi notification mở menu */
.header-notification-container.active .notification-menu {
  opacity: 1;
  transform: translateY(0);
  pointer-events: auto;
}

.dropdown-menu {
  position: absolute;
  top: 44px;
  right: 0;
  min-height: 60px;
  min-width: 180px;
  background-color: #fff;
  border: 1px solid #ddd;
  padding: 8px 0;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
  z-index: 9999;
  opacity: 0;
  transform: translateY(-10px);
  pointer-events: none;
  transition: opacity 0.3s ease, transform 0.3s ease;
}
.header-notification-container .notification-menu {
  position: fixed;
  top: 56px;
  right: 0;
  min-width: 360px;
  background-color: #fff;
  border: 1px solid #ddd;
  padding: 8px 0;
  box-shadow: -4px 4px 12px rgba(0, 0, 0, 0.1);
  z-index: 100;
  opacity: 0;
  transform: translateY(-10px);
  pointer-events: none;
  transition: opacity 0.3s ease, transform 0.3s ease;
}
.header-notification-container .notification-menu p {
  padding: 10px 16px;
  color: #666;
  font-size: 14px;
  border-bottom: 1px solid #eee;
}
.dropdown-menu ul {
  list-style: none;
  margin: 0;
  padding: 0;
}

.dropdown-menu li {
  padding: 0;
}

.dropdown-menu a {
  display: block;
  padding: 10px 16px;
  color: #333;
  text-decoration: none;
  font-size: 14px;
  transition: background-color 0.2s ease, color 0.2s ease;
}

.dropdown-menu a:hover {
  background-color: #f2f2f2;
  color: #000;
}

.burger-toggle {
  display: none;
  font-size: 1.5rem;
  cursor: pointer;
  padding: 0 1rem;
  align-items: center;
}

.burger-menu {
  display: none;
  position: absolute;
  top: 3.5rem;
  left: 0;
  width: 100%;
  background-color: #fff;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
  z-index: 999;
}

.burger-menu ul {
  list-style: none;
  margin: 0;
  padding: 0.5rem 1rem;
}

.burger-menu li {
  padding: 0.75rem 0;
  border-bottom: 1px solid #eee;
}

.burger-menu a {
  text-decoration: none;
  color: #333;
  font-weight: bold;
  font-size: 1rem;
}
.messenger-container {
  position: fixed;
  bottom: 0;
  right: 20px;
  width: 700px;
  height: 500px;
  background: #fff;
  border-radius: 12px;
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.15);
  display: flex;
  overflow: hidden;
  display: none;
  z-index: 9999;
}

/* Sidebar */
.messenger-sidebar {
  width: 35%;
  background: #f3f3f3;
  border-right: 1px solid #ddd;
  display: flex;
  flex-direction: column;
}

.sidebar-header {
  height: 65px;
  padding: 15px;
  font-weight: bold;
  background: #007bff;
  color: #fff;
}

.chat-list {
  flex: 1;
  overflow-y: auto;
}

.chat-item {
  display: flex;
  padding: 12px;
  cursor: pointer;
  border-bottom: 1px solid #ddd;
}

.chat-item:hover {
  background: #e6e6e6;
}

.chat-avatar {
  width: 45px;
  height: 45px;
  border-radius: 50%;
  margin-right: 10px;
}

.chat-info p {
  margin: 0;
}

/* Chat window */
.messenger-chat {
  width: 65%;
  display: flex;
  flex-direction: column;
}

.chat-header {
  display: flex;
  flex-direction: row;
  justify-content: space-between;
  height: 65px;
  padding: 15px;
  background: #007bff;
  color: #fff;
  font-weight: bold;
}
.chat-header span {
  display: flex;
  align-items: center;
  padding: 6px;
  font-size: larger;
  cursor: pointer;
}

.chat-body {
  flex: 1;
  padding: 15px;
  overflow-y: auto;
  background: #fafafa;
}

.message {
  max-width: 70%;
  padding: 10px 14px;
  margin-bottom: 12px;
  border-radius: 10px;
}

.message.user {
  background: #007bff;
  color: #fff;
  margin-left: auto;
}

.message.other {
  background: #e0e0e0;
}

/* Footer */
.chat-footer {
  display: flex;
  padding: 10px;
  border-top: 1px solid #ddd;
}

.chat-footer input {
  flex: 1;
  padding: 10px;
  border-radius: 8px;
  border: 1px solid #ccc;
}

.chat-footer button {
  margin-left: 10px;
  padding: 10px 15px;
  background: #007bff;
  color: #fff;
  border: none;
  border-radius: 8px;
}



/* Responsive hiển thị burger */
@media (max-width: 768px) {
  .header-nav-center {
    display: none !important;
  }

  .burger-toggle {
    display: flex;
  }

  .burger-menu.active {
    display: block;
  }
}
@media (max-width: 1024px) {
  .header-nav-center ul {
    gap: 1rem;
  }

  .header-logo h1 {
    font-size: 1.75rem;
  }

  .header-search.active {
    width: 12rem;
  }
}

@media (max-width: 480px) {
  .header-logo h1 {
    font-size: 1.5rem;
  }

  .header-search.active {
    width: 10rem;
  }

  .burger-menu a {
    font-size: 0.875rem;
  }

  .header-user-container .user-name-popup {
    font-size: 12px;
  }
}
# Performance optimization
# API improvements
/* Multi-line comment block
// Database optimization completed
// UI/UX improvements added
// Unit tests added for better coverage
// Security enhancements integrated
// Unit tests added for better coverage
// Configuration settings optimized
// Logging mechanism enhanced
// Database optimization completed
// API improvements and error handling
// Logging mechanism enhanced
// Code documentation updated
// Feature flag implementation
// Configuration settings optimized
// UI/UX improvements added
/* Multi-line comment block
   Code review suggestions applied */
// UI/UX improvements added
// Logging mechanism enhanced
   Additional implementation details
/* Multi-line comment block