* {
    margin: 0;
    border: 0;
    padding: 0;
}
body {
    background-color: rgba(58, 129, 134, 0.87);
}
#c1 {
    
}
#div1 {
    position: absolute;
    top:0;
    left:0;
    background-color: rgba(48, 90, 57, 0.7);
    text-align: center;
    display: none;
}
#btn1 {
    background-color: bisque;
    box-sizing: border-box;
    border: 1px solid greenyellow;
    padding: 10px;
    width:100px;
    height:40px;
    border-radius: 15px;
    position: absolute;
    left: 50%;
    top: 50%;
    margin-top: -20px;
    margin-left: -50px;
}