*{
    margin:0;
    padding:0;
    box-sizing: border-box;
}
html {
    scroll-behavior: smooth;
}
body{
    font-family: arial;
    background: url("https://wallpaperplay.com/walls/full/4/e/6/329978.jpg");
     background-attachment: fixed;
}
.content{
    margin-top: 100px;
    height: 200vh;
    padding: 20px;
    text-align:justify;
    font-size: 24px;
    line-height: 40px;
}
.scrolltopbtn{
    display:none;
    padding: 12px 20px;
    position: fixed;
    right: 20px;
    bottom: 20px;
    background: #424242;
    color: white;
    border: none;
    border-radius: 6px;
    transition: 0.15s;
}
.scrolltopbtn:hover{
    background: #000;
}