style.css

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

html, body {
    margin: 0;
    padding: 0;
}

body {
    color: #333;
    font-family: Verdana, Arial, sans-serif;
    font-size: 12px;
    margin: 0;
}

a {
    color: #54b4e8;
}

a:hover {
    color: #44a0d2;
}

label {
    display: inline-block;
    margin-right: 0.5rem;
    text-align: right;
    width: 3rem;
}

label:after {
    content: ':';
}

.boxed {
    border: 1px solid #ccc;
    border-radius: 3px;
    padding: .5em;
    font-family: Inconsolata, Consolas, Monaco, monospace;
    font-size: 1.2em;
}

select {
	height: 32px;
}

textarea {
    white-space: pre;
    word-wrap: normal;
    height: 200px;
    width: 100%;
}

input[type="submit"] {
    background-color: #f8f8f8;
    background-image: -webkit-gradient(linear, 0 0, 0 100%, from(#f8f8f8), to(#eee));
    background-image: -webkit-linear-gradient(top, #f8f8f8, #eee);
    background-image: -o-linear-gradient(top, #f8f8f8, #eee);
    background-image: linear-gradient(to bottom, #f8f8f8,#eee);
    background-image: -moz-linear-gradient(top, #f8f8f8, #eee);
    border: 1px solid #ccc;
    color: #333;
    cursor: pointer;
    text-shadow: 1px 1px 0 rgba( 255, 255, 255, .8 );
}

h1 {
    background: #f5f5f5;
    border-bottom: 1px solid #eee;
    color: #555;
    margin: 0;
    padding: 1rem;
    text-shadow: 1px 1px 0 rgba( 255, 255, 255, .8 );
}

h2 {
    border-bottom: 1px solid #f8f8f8;
    color: #555;
    clear: both;
    letter-spacing: 0.05em;
    padding: 0.5rem 0;
}

footer {
    border-top: 1px solid #eee;
    color: #ccc;
    opacity: 0.5;
    padding: 1rem;
}

.cols {
    margin: 1rem;
    overflow: hidden;
}

.col {
    width: 50%;
    float: left;
    padding: 0.5rem;
}

.col:first-child {
	padding-left: 0;
}

.col:last-child {
	padding-right: 0;
}

.randomness {
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    overflow: hidden;

    background: #f5f5f5;
    border-top: 1px solid #eee;
}

.randomness-box {
    width: 30em;
    background: transparent;
    border: none;
}

.randomness > h2 {
    display: none;
}

.randomness > ul {
    list-style-type: none;
    margin: 0;
    padding: 0;
    width: 90em;
}

.randomness > ul > li {
    float: left;
    width: 45em;
}

.math {
    margin: 1em 0;
}

.math-solution {
    display: inline-block;
    margin: 1em 0;
    min-width: 100px;
}

.error {
    color: red;
}

.full-width {
    width: 100%;
}