html{
    height: 100%;
    background: radial-gradient(circle, #fff 19%, #999);
    background-size: cover;
}

body{
    color: #333;
    font-family: sans-serif;
    padding: 20px;
}

.left{
    float: left;
}

.right{
    float: right;
}

#calc{
    
    width: 335px;
    height: 335px;
    font-weight: bold;
    border-bottom: 17px solid #78B3D5;
    /* overflow: hidden; */
    /* display: block; */
    padding: 35px;
    border-radius: 9px;
    background: #A9D3EB;

    margin: auto;
    position: absolute;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
}

div{
    box-sizing: border-box;
    overflow: hidden;
}

#calc .btn{
    margin: 3px;
    float: left;
    width: 60px;
    text-align: center;
    padding: 10px;
    border-radius: 6px;
    border: 1px solid #b1c6cf;
    border-bottom: 4px solid #7f99a5;
    transition: all 0.1s ease;
}

#calc .btn:active{
    margin-top: 6px;
    border: 1px solid #ee2e20;
}

#calc .top{
    overflow: hidden;
}

#calc .display{
    font-size: 160%;
    line-height: 138%;
    width: 195px;
    height: 47px;
    float: left;
    background-color: #e3f4c9;
    border-radius: 4px;
    font-weight: normal;
    text-align: right;
    box-shadow: inset 0px 3px rgba(156, 50, 50, 0.1);
}

#calc .numbers{
    clear: both;
}

#calc .numbers .btn{
    background-color: #ffffff;
}

#calc .numbers .btn:hover{
    background-color: #f0f0f0;
}

#calc .operator-group{
    width: 66px;
}

#calc .operator-group .btn{
    color: #fff;
    background-color: #697978;
    float: right;
    vertical-align: baseline;
}

#calc .operator-group .btn:hover{
    background-color: #465A59;
}

#calc .reset{
    background-color: #fff68c;
}

#calc .reset:hover{
    background-color: #f1e885;
}

#calc .numbers .equal{
    background-color: #ff8c6e;
}

#calc .numbers .equal:hover{
    background-color: #e97354;
}