/* Biến màu */
:root {
  --primary-color: #1A237E;
  --secondary-color: #FFD700;
  --text-color-light: #FFFFFF;
  --text-color-dark: #333333;
  --button-hover-darken: rgba(0, 0, 0, 0.1);
  --button-active-darken: rgba(0, 0, 0, 0.2);
}

/* Reset cơ bản */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  line-height: 1.6;
  color: var(--text-color-dark);
  background-color: #f4f4f4;
}

a {
  text-decoration: none;
  color: var(--primary-color);
}

ul {
  list-style: none;
}

/* Header */
.site-header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  min-height: 60px;
  background-color: var(--primary-color);
  color: var(--text-color-light);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
  z-index: 1000;
  padding: 10px 20px;
  display: flex;
  flex-direction: column;
  justify-content: center;
}

.header-container {
  max-width: 1200px;
  margin: 0 auto;
  width: 100%;
}

.header-top-area {
  display: flex;
  align-items: center;
  justify-content: space-between;
  min-height: 40px;
}

.logo {
  font-size: 2.2em;
  font-weight: bold;
  color: var(--secondary-color);
  text-decoration: none;
  flex-shrink: 0;
  text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.3);
  letter-spacing: 1px;
  transition: color 0.3s ease;
}

.logo:hover {
  color: #FFEA00; /* Slightly brighter yellow */
}

/* Desktop Navigation */
.main-nav {
  display: block;
  flex-grow: 1;
  margin: 0 20px;
}

.main-nav ul {
  display: flex;
  justify-content: center;
  gap: 25px;
}

.main-nav li a {
  color: var(--text-color-light);
  font-weight: 600;
  padding: 8px 0;
  display: block;
  position: relative;
  transition: color 0.3s ease;
}

.main-nav li a::after {
  content: '';
  position: absolute;
  left: 0;
  bottom: 0;
  width: 0%;
  height: 3px;
  background-color: var(--secondary-color);
  transition: width 0.3s ease;
}

.main-nav li a:hover::after, .main-nav li a.active::after {
  width: 100%;
}

.main-nav li a:hover {
  color: var(--secondary-color);
}

/* Header Buttons */
.header-buttons-desktop {
  display: flex;
  gap: 10px;
  flex-shrink: 0;
}

.btn {
  padding: 10px 20px;
  border-radius: 25px;
  font-weight: bold;
  text-align: center;
  text-decoration: none;
  transition: all 0.3s ease;
  box-shadow: 0 4px 8px rgba(0, 0, 0, 0.2);
  border: none;
  cursor: pointer;
  white-space: nowrap;
}

.btn-primary {
  background-color: #FF4081; /* Pink/Red */
  color: var(--text-color-light);
}

.btn-primary:hover {
  background-color: #F50057; /* Darker Pink/Red */
  box-shadow: 0 6px 12px rgba(0, 0, 0, 0.3);
  transform: translateY(-2px);
}

.btn-secondary {
  background-color: #64FFDA; /* Teal */
  color: var(--primary-color);
}

.btn-secondary:hover {
  background-color: #1DE9B6; /* Darker Teal */
  box-shadow: 0 6px 12px rgba(0, 0, 0, 0.3);
  transform: translateY(-2px);
}

.btn-tertiary {
  background-color: #FFC107; /* Amber */
  color: var(--primary-color);
}

.btn-tertiary:hover {
  background-color: #FFB300; /* Darker Amber */
  box-shadow: 0 6px 12px rgba(0, 0, 0, 0.3);
  transform: translateY(-2px);
}

/* Hamburger Menu (Mobile) */
.hamburger-menu {
  display: none; /* Hidden on desktop */
  background: none;
  border: none;
  cursor: pointer;
  padding: 0;
  width: 30px;
  height: 24px;
  position: relative;
  z-index: 1001; /* Ensure it's above other elements */
  flex-shrink: 0;
}

.hamburger-menu .bar {
  display: block;
  width: 100%;
  height: 3px;
  background-color: var(--secondary-color);
  margin: 5px 0;
  transition: all 0.3s ease;
}

.hamburger-menu.active .bar:nth-child(1) {
  transform: translateY(8px) rotate(45deg);
}

.hamburger-menu.active .bar:nth-child(2) {
  opacity: 0;
}

.hamburger-menu.active .bar:nth-child(3) {
  transform: translateY(-8px) rotate(-45deg);
}

/* Mobile Navigation */
.mobile-nav {
  display: none; /* Hidden by default */
  position: fixed;
  top: 0;
  left: -100%; /* Start off-screen */
  width: 80%;
  max-width: 300px;
  height: 100%;
  background-color: var(--primary-color);
  padding-top: 80px; /* Space for header top */
  box-shadow: 2px 0 10px rgba(0, 0, 0, 0.2);
  transition: left 0.3s ease-in-out;
  z-index: 999; /* Below hamburger, above buttons */
  overflow-y: auto;
}

.mobile-nav.active {
  left: 0;
}

.mobile-nav ul {
  padding: 20px 0;
}

.mobile-nav li a {
  display: block;
  padding: 15px 20px;
  color: var(--text-color-light);
  font-size: 1.1em;
  border-bottom: 1px solid rgba(255, 255, 255, 0.1);
  transition: background-color 0.3s ease;
}

.mobile-nav li:last-child a {
  border-bottom: none;
}

.mobile-nav li a:hover, .mobile-nav li a.active {
  background-color: rgba(255, 255, 255, 0.1);
  color: var(--secondary-color);
}

.header-buttons-mobile {
  display: none; /* Hidden on desktop */
  justify-content: center;
  gap: 10px;
  padding: 10px 0;
  background-color: var(--primary-color);
  z-index: 1000; /* Same as header, above content but below mobile nav */
  box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
}

/* Footer */
.site-footer {
  background-color: var(--primary-color);
  color: var(--text-color-light);
  padding: 40px 20px;
  font-size: 0.9em;
}

.footer-container {
  max-width: 1200px;
  margin: 0 auto;
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 30px;
}

.footer-column {
  flex: 1;
  min-width: 250px;
}

.footer-logo {
  font-size: 2em;
  font-weight: bold;
  color: var(--secondary-color);
  text-decoration: none;
  display: block;
  margin-bottom: 15px;
  text-shadow: 1px 1px 3px rgba(0, 0, 0, 0.2);
}

.footer-info p {
  line-height: 1.8;
  color: rgba(255, 255, 255, 0.8);
}

.footer-column h3 {
  font-size: 1.3em;
  margin-bottom: 20px;
  color: var(--secondary-color);
  position: relative;
}

.footer-column h3::after {
  content: '';
  position: absolute;
  left: 0;
  bottom: -5px;
  width: 50px;
  height: 2px;
  background-color: var(--secondary-color);
}

.footer-nav li {
  margin-bottom: 10px;
}

.footer-nav a {
  color: rgba(255, 255, 255, 0.8);
  transition: color 0.3s ease;
}

.footer-nav a:hover {
  color: var(--secondary-color);
}

.footer-contact p {
  margin-bottom: 10px;
  color: rgba(255, 255, 255, 0.8);
}

.footer-bottom {
  text-align: center;
  margin-top: 40px;
  padding-top: 20px;
  border-top: 1px solid rgba(255, 255, 255, 0.1);
  color: rgba(255, 255, 255, 0.6);
}

/* Responsive Design */
@media (max-width: 1024px) {
  .main-nav ul {
    gap: 15px;
  }
  .main-nav li a {
    font-size: 0.95em;
  }
  .header-buttons-desktop .btn {
    padding: 8px 15px;
    font-size: 0.9em;
  }
}

@media (max-width: 768px) {
  .site-header {
    padding: 10px 15px;
    min-height: auto;
  }

  .header-top-area {
    justify-content: space-between;
    order: 1;
  }

  .hamburger-menu {
    display: block;
    order: 1; /* Leftmost */
  }

  .logo {
    order: 2; /* Centered */
    flex-grow: 1;
    text-align: center;
    font-size: 1.8em;
  }

  .main-nav, .header-buttons-desktop {
    display: none; /* Hide desktop nav and buttons */
  }

  .header-buttons-mobile {
    display: flex; /* Show mobile buttons */
    order: 2; /* Below header-top-area */
    width: 100%;
    padding: 10px 15px;
    background-color: var(--primary-color);
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
    justify-content: space-around;
  }

  .header-buttons-mobile .btn {
    flex: 1;
    margin: 0 5px;
    font-size: 0.9em;
    padding: 8px 10px;
  }

  .footer-container {
    flex-direction: column;
    gap: 20px;
  }

  .footer-column {
    min-width: unset;
  }

  .footer-column h3 {
    margin-top: 20px;
  }
}

@media (max-width: 480px) {
  .logo {
    font-size: 1.6em;
  }

  .header-buttons-mobile .btn {
    font-size: 0.8em;
    padding: 6px 8px;
  }
}