body {
  width: 400px;
  margin: 5px;
  font-family: Arial, Helvetica, sans-serif;
  background-color: beige;
    background-color: #f5f5f5;
    padding:0px;
    margin:0px;
    height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
}

table, th, td {
  border: 1px solid black;
  width: max;
  border-collapse: collapse;
  padding: 3px;
}
th {
  text-align: left; 
}
td {
  font-weight: normal;
}


.topnav {
    max-width: 400px;
  overflow: hidden;
  background-color: #333;
}
.GasIng {
    max-width: 800px;
  overflow: hidden;
  background-color: #333;
}

.topnav sr {
  float: center;
  display: block;
  color: #f2f2f2;
  text-align: center;
  padding: 14px 16px;
  text-decoration: none;
  font-size: 17px;
}

.topnav a {
  float: left;
  display: block;
  color: #f2f2f2;
  text-align: center;
  padding: 14px 10px;
  text-decoration: none;
  font-size: 15px;
}

.topnav a:hover {
  background-color: #ddd;
  color: black;
}

.topnav a.active {
  background-color: #4CAF50;
  color: white;
}

.topnav .icon {
  display: none;
}

@media screen and (max-width: 300px) {
  .topnav a:not(:first-child) {display: none;}
  .topnav a.icon {
    float: right;
    display: block;
  }
}

@media screen and (max-width: 300px) {
  .topnav.responsive {position: relative;}
  .topnav.responsive .icon {
    position: absolute;
    right: 0;
    top: 0;
  }
  .topnav.responsive a {
    float: none;
    display: block;
    text-align: center;
  }
}