: center;
  align-items: center;
  z-index: 1000;
  transition: background-color 0.3s, box-shadow 0.3s, transform 0.3s;
}
.go-top-btn:hover {
  background-color: #000000;
  box-shadow: 0px 6px 12px rgba(0, 0, 0, 0.25);
  transform: translateY(-2px);
}

    </style>
</head>

<body>

      <!-- scroll to top button  -->
  <button class="go-top-btn">
    <img   width="25px" src="arrow_upper.png" alt="go top">
</button>
    <header class="header" id="header">
        <div class="logo">
            <a href="/"> 