style.css

html, body {
    height: 100%;
    width: 100%;
    background: #9c27b0;
    margin: 0;
    padding: 0;
    font-family: 'Raleway', Arial, Helvetica, sans-serif;
    color: white;
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
}

*, *:before, *:after {
    -webkit-box-sizing: inherit;
    -moz-box-sizing: inherit;
    box-sizing: inherit;
}

.container {
    width: 100%;
    max-width: 540px;
    margin: 0 auto;
    padding: 20px;
    padding-top: 80px;
}

h1 {
    display: block;
    float: left;
    font-weight: 100;
    font-size: 3em;
    margin: 0;
}

.actions {
    float: right;
    list-style: none;
    position: absolute;
    right: 0;
    top: 0;
    bottom: 0;
}

.scores {
    float: right;
    text-align: right;
}

.score {
    position: relative;
    display: inline-block;
    background: white;
    padding: 15px 25px;
    font-size: 1.5em;
    line-height: 3em;
    font-weight: bold;
    border-radius: 3px;
    color: #9c27b0;
    margin-top: 8px;
    text-align: center;
    margin-left: 5px;
    width: 3em;
    height: 2.5em;
}

.score span {
    position: absolute;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
    padding: 4px;
    padding-top: 10px;
}

.score span::after {
    position: absolute;
    width: 100%;
    top: 10px;
    left: 0;
    text-transform: uppercase;
    font-size: 13px;
    line-height: 13px;
    text-align: center;
}

.current.score span::after {
    content: 'score'
}

.best.score span::after {
    content: 'best';
}

.info {
    clear: left;
}

.info p {
    margin-bottom: 20px;
    float:left;
    line-height: 3em;
}

a {
    color: white;
}

a.new {
    text-transform: uppercase;
    border-radius: 2px;
    border: 1px solid white;
    padding: 0 28px;
    text-decoration: none;
    height: 3em;
    line-height: 3em;
    cursor: pointer;
    display: block;
    text-align: center;
    float: right;
}

a.new:hover {
    text-decoration: none;
    background: white;
    color:#9c27b0;
    cursor: pointer;
}

.container, .panel, .grid {
    overflow: auto;
}

.panel {
    position: relative;
    clear: left;
}

.cell {
    height: 20%;
    width: 20%;
    background: white;
    color: #9c27b0;
    display: block;
    padding: 10%;
    box-sizing: border-box;
    float: left;
    position: relative;
}

.cell:first-child, .cell:nth-child(5n + 1) {
    clear: left;
}

.cell span {
    position: absolute;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
    border: 1px solid #9c27b0;
    font-weight: 700;
}

.highlighted, .selected, .correct {
    background: #68efad;
}

.wrong {
    background: #ff8a80;
}

.missed {
    background: #ffd180;
}

.correct::after, .wrong::after, .missed::after {
    position: absolute;
    bottom: 4px;
    right: 4px;
    color: rgba(0,0,0,0.38);
}

.correct::after {
    content: 'correct';
}

.wrong::after {
    content: 'wrong';
}

.missed::after {
    content: 'missed';
}

header, footer {
    overflow: auto;
}

main {
    margin-bottom: 20px;
}

footer {
    padding: 20px 0;
    text-align: center;
}

.cycle::before {
    background: url('http://cycle.js.org/img/cyclejs_logo.svg');
    content: '';
    display: inline-block;
    width: 20px;
    height: 20px;
    vertical-align: middle;
    margin-right: 3px;
}

footer div {
    margin-top: 10px;
}