styles.css

* {
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
}

html, body {
    margin:0px;
    padding:0px;
    font-size: 14px;
    font-family:Arial,Verdana,Helvetica,sans-serif;
    border-style:none;
}

table {
    margin-left: auto;
    margin-right:  auto;
    width: 100%;
}

td {
    text-align: center;
}

tr {
    height: 50px;
}

.tr {
    height: 120px;
}

.td {
    font-size: 25px;
}

.calc {
    padding: 15px 25px 15px 25px;
    background-color: #ebebeb;
    border-radius: 5px;
    border: 1px solid #000000;
    margin: auto;
    max-width: 500px;
}


#smd-code {
    height: 90px;
    font-size: 60px;
    width: 200px;
    text-align: center;
    background-color: #000000;
    border-radius: 10px;
    color:#ffffdd;
    padding-bottom:5px;
    border: none;
}

#result {
    font-size: 20px;
    color: crimson;
    font-weight: 700;
}