html,
body {
    height: 100%;
}

body {
    /* Permalink - use to edit and share this gradient: https://colorzilla.com/gradient-editor/#ffffff+0,bfbfbf+100 */
    background: #ffffff;
    /* Old browsers */
    background: -moz-radial-gradient(center, ellipse cover, #ffffff 0%, #bfbfbf 100%);
    /* FF3.6-15 */
    background: -webkit-radial-gradient(center, ellipse cover, #ffffff 0%, #bfbfbf 100%);
    /* Chrome10-25,Safari5.1-6 */
    background: radial-gradient(ellipse at center, #ffffff 0%, #bfbfbf 100%);
    /* W3C, IE10+, FF16+, Chrome26+, Opera12+, Safari7+ */
    filter: progid:DXImageTransform.Microsoft.gradient(startColorstr='#ffffff', endColorstr='#bfbfbf', GradientType=1);
    /* IE6-9 fallback on horizontal gradient */
}

.calculator {
    background-color: #353535;
    width: 300px;
    padding: 15px;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    text-align: center;
    border-radius: 20px;
    box-shadow: 0 6px 0 #a1a1a1, 0 8px 10px rgba(0, 0, 0, 0.75)
}

.result {
    background-color: #cecfac;
    color: #3b3b32;
    width: 90%;
    margin: 8px 0 20px 10px;
    text-align: right;
    height: 50px;
    line-height: 50px;
    font-size: 36px;
    padding-right: 10px;
    overflow: hidden;
    font-family: Arial, Helvetica, sans-serif;
    box-shadow: inset 0 0 8px rgba(0, 0, 0, 0.5), inset 0 2px 0 #a1a1a1;
}

ul {
    padding: 0;
    margin: 0;

}

ul li {
    list-style: none;
    background-color: #4e4e4e;
    padding: 10px;
    width: 15%;
    float: left;
    cursor: pointer;
    color: white;
    font-family: Arial, Helvetica, sans-serif;
    font-weight: bold;
    margin: 5px;
    font-size: 20px;
    border-radius: 5px;
    box-shadow: 0 4px 0 #a5a5a5;
}

ul li:active {
    position: relative;
    top: 5px;
    box-shadow: 0 1px 0 #a5a5a5;
}

ul li:nth-child(16) {
    height: 75px;
    line-height: 75px;
}

ul li:nth-child(17) {
    margin-top: -48px;
    width: 65%;
}

.signature {
    color: #fff;
    font-size: 0.75rem;
    font-family: Arial, Helvetica, sans-serif;
    text-align: right;
    position: relative;
    top: 8px;
    left: -5px;
    z-index: -1;
}