#gotopBtn {
 position: fixed;
 bottom: 80px;
 right: 15px;
 width: 50px;
 height: 50px;
 background: #c8102e;
 color: white;
 border: none;
 border-radius: 50%;
 font-size: 22px;
 line-height: 50px;
 text-align: center;
 box-shadow: 0 2px 10px rgba(0,0,0,0.25);
 cursor: pointer;
 z-index: 9999;
 opacity: 0;
 visibility: hidden;
 transition: opacity 0.3s, visibility 0.3s;
}
#gotopBtn.show {
 opacity: 1;
 visibility: visible;
}
#gotopBtn:hover {
 background: #a81020;
}