html, body {
    height: 100%;
    margin: 0;
    padding:0;
    background-color: black;
}

img {
  width :100%;
  height :auto;
}

#btn{
    width : 165px;
    height : 179px;
    padding:0;
    margin:0;
    cursor :pointer;
}

#mainbody {
    background-image: url("bg.jpg");
}