.center {
    margin: 0;
    position: absolute;
    top: 50%;
    left: 50%;
    -ms-transform: translate(-50%, -50%);
    transform: translate(-50%, -50%);
  }



#btn{
    display: none;
    size: 100px;
}
#btn, #btn2 {
    position: absolute;
    top: 75%;
    left: 50%;
    transform: translate(-50%, -50%);
       
}

#btn3 {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
       
}



.iframe {
    margin: 0;
    width: 100%;
    height: 100%;
}

.center{
    margin: 0;
    position: absolute;
    top: 50%;
    left: 50%;
    -ms-transform: translate(-50%, -50%);
    transform: translate(-50%, -50%);
    
}

body {
    background-color: black;
}

#btn, #btn2, #btn3 {
        font-size: 25px;
        padding: 10px;
            
}