Style.css

body
{
    background-color: #282a35;
}

#h11
{
    text-align: center; text-decoration: solid; color: antiquewhite;
    margin-top: 100px; font-size: 80px;
}

#h12
{
    color: #ffc0bf; text-align: center; margin-top: 45px;
}

.topnav .search-container {
    float: center;
  }
  
  .topnav input[type=text] {
    padding: 6px;
    margin-top: 8px;
    margin-left: 636px;
    font-size: 17px;
    border: none;
  }
  
  .topnav .search-container button {
    float: center;
    padding: 6px 10px;
    margin-top: 45px;
    margin-right: 16px;
    background: #04aa6d;
    font-size: 17px;
    border: none;
    cursor: pointer;
  }
  
  .topnav .search-container button:hover {
    background: #ccc;
  }

  @media screen and (max-width: 600px) {
    .topnav .search-container {
      float: none;
    }
    .topnav a, .topnav input[type=text], .topnav .search-container button {
      float: none;
      display: block;
      text-align: left;
      width: 100%;
      margin: 0;
      padding: 14px;
    }
    .topnav input[type=text] {
      border: 1px solid #ccc;  
    }
  }