#gioi-thieu {
    background-color: #F3FDE8;
    padding: 20px;
}


#lien-he {
    background-image: url("background.jpg"); 
    background-repeat: repeat;
    text-align: center;
    padding: 20px;
}

#lien-he-title {
    color: white;
    padding: 15px;
    border-radius: 8px;
    display: inline-block;
    background-image: url("background.png");
    background-repeat: repeat;
}


table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 20px;
}

th, td {
    border: 1px solid black;
    padding: 10px;
    text-align: center;
}

nav, footer {
    background-color: #d4f2f4;
    color: #0b0848;
    padding: 10px;
    text-align: center;
}

nav a {
    margin: 0 15px;
    text-decoration: none;
    color: #0b0848;
    font-weight: bold;
}

footer p {
    margin: 0;
}

#backToTop {
  position: fixed;
  bottom: 30px;
  right: 30px;
  width: 50px;
  height: 50px;
  background: linear-gradient(135deg, #4ac1ff, #0077cc);
  color: white;
  font-size: 20px;
  font-weight: bold;
  border: none;
  border-radius: 50%;
  box-shadow: 0 4px 8px rgba(0, 0, 0, 0.3);
  cursor: pointer;
  display: none;           /* ẩn lúc đầu */
  transition: all 0.3s ease;
  z-index: 1000;
}

#backToTop:hover {
  transform: scale(1.1);
  background: linear-gradient(135deg, #0077cc, #4ac1ff);
  box-shadow: 0 6px 12px rgba(0, 0, 0, 0.4);
}

.avatar {
  display: block;
  margin: 0 auto;
  width: 300px;
  height: 250px;
  border-radius: 8px;
  transition: transform 0.3s ease, border 0.3s ease;
}

.avatar.hovered {
  transform: scale(1.05);
  border: 3px solid #0888c9;
}