body {
    font-family: 'Comic Sans MS', cursive, sans-serif;
    margin: 0;
    padding: 0;
    background-color: #f8f8f8;
}
header{
    color: #fff;
    text-align: center;
        background: linear-gradient(
            to top left,
            rgb(166, 224, 166),
            rgb(95, 203, 95),
            rgb(26, 223, 26)   ,
            rgb(3, 171, 3),
            rgb(5, 101, 5)
        );
}
.header-logo-img{
  font-size: 50px;
}
#langSelect {
  position: absolute;
  top: 70px;
  right: 20px;
  padding: 10px;
  font-size: 16px;
  border: none;
  border-radius: 5px;
  background-color: #f8f9fa;
  color: #495057;
  box-shadow: 0 0 10px rgba(0,0,0,0.15);
}
.container {
  width: 100%;
  max-width: 800px;
  margin: 0 auto;
  padding: 15px;
  box-shadow: 0 0 10px rgba(0, 0, 0, 0.3);
}

.main {
  background-color: #f8f9fa;
  border-radius: 5px;
  padding: 20px;
}

.input-group {
  display: flex;
  align-items: center;
  margin-bottom: 15px;
}

.input-group-text {
    flex: 1;
    padding: 10px;
    font-weight: bold;
    color: #333;
    border: 1px solid #c6bfbf;
    border-right: none;
    border-radius: 4px 0 0 4px;
    background-color: #f5f5f5;
}

.form-control {
    flex: 1;
    padding: 10px;
    border-radius: 10px;
    border: 1px solid #ddd;
}

.form-select {
  margin-left: 10px;
  border-radius: 7px;
  border: 1px solid #ccc; 
  cursor: pointer;
  color: #fff;
  background-color: #999;
}

.form-select:hover{
    background-color: #fff;
    color: #555;
}
.btn {
  width: 100px;
  padding: 5px;
  border: none;
  border-radius: 5px;
  cursor: pointer;
}

.btn-reset {
  background-color: #888;
  color: #fff;
}
.btn-reset:hover{
    background-color: #555;
}
.btn-success {
  background-color: #29a96d;
  color: #fff;
}

.btn-success:hover {
    background-color: #21cf47;
} 

.ket-qua {
  color: #198754;
  font-weight: bold;
}

  .reference-table {
    padding: 20px 0;
    text-align: left;
    border-top: 2px solid #555;
    margin-top: 30px;
  }
  
  .reference-table p {
    margin: 5px ;
  }

  .reference-table h3 {
    color: green;
    margin-bottom: 15px;
    text-align: center;
  }
  .note{
    color: black;
  }
  footer {
    background-color: #e7e7e0; 
    color: #333; 
    padding: 5px;
    font-size: 14px; 
    text-align: center; 
    border-top: 2px solid #a49999;
  }
  
  #backToTopBtn {
    display: none;
    position: fixed;
    bottom: 20px;
    right: 20px;
    background-color: rgb(9, 226, 9);
    color: #fff;
    border: none;
    border-radius: 50%;
    padding: 10px;
    cursor: pointer;
    font-size: 16px;
}

#backToTopBtn:hover {
    background-color: rgb(12, 192, 12);
    color: #444;
}