style.css

body {
    font-family: sans-serif;
    color: #444;
    background-color: #f9f9f9;
}
main {
    max-width: 820px;
    margin: auto;
}
.mathfield {
    border: 1px solid #ddd;
    padding:5px;
    margin: 10px 0 10px 0;
    border-radius:5px;
    background-color: #fff;
}
.output {
    padding:5px;
    margin: 20px 0 20px 0;
    border-radius:5px;
    border: 1px solid #000;

    font-family: "Source Code Pro", Menlo, "Bitstream Vera Sans Mono", Monaco, Courier, "Andale Mono", monospace;
    color: #f0c674;
    background: #35434e;
}
label {
    font-weight: bold;
}
button {
    background: none;
    border:	1px solid rgba(0, 0, 0, .12);
    border-radius: 4px;
    color: #0066ce;
    fill: #0066ce;
    position: relative;
    height: 36px;
    line-height: 36px;
    margin: 0 18px 0 0;
    min-width: 64px;
    padding: 0 16px;
    display: inline-block;
    overflow: hidden;
    will-change: box-shadow;
    transition: box-shadow .2s cubic-bezier(.4,0,1,1),background-color .2s cubic-bezier(.4,0,.2,1),color .2s cubic-bezier(.4,0,.2,1);
    outline: none;
    cursor: pointer;
    text-decoration: none;
    text-align: center;
    vertical-align: middle;
    user-select: none;

    font-size: 16px;
    letter-spacing: 0.08929em;
    text-transform: uppercase;
    box-shadow:  0px 1px 5px 0px rgba(0, 0, 0, 0.2),
        0px 2px 2px 0px rgba(0, 0, 0, 0.14),
        0px 3px 1px -2px rgba(0, 0, 0, 0.12); 
    }
button:first-child {
    margin-left: 0;
}
button:hover {
    background-color: rgba(0,0,0,0.08);
}
button:active{
    background-color: white;
}