.kana {
    text-align: center;
    font-size: 100px;
    width: 150px; /* responsive? */
    height: 150px;
}

.button {
    font-family: Sans-Serif;
    font-size: 20px;
    text-align: center;
    text-decoration: none;
    padding: 2px 6px 2px 6px;
    background-color: #ccc;
    color: #333;
    border-top: 1px solid #eee;
    border-left: 1px solid #eee;
    border-right: 1px solid #999;
    border-bottom: 1px solid #999;
}

.button:hover {
    font-family: Sans-Serif;
    font-size: 20px;
    text-align: center;
    text-decoration: none;
    padding: 2px 6px 2px 6px;
    background-color: #ccc;
    color: #333;
    border-top: 1px solid #999;
    border-left: 1px solid #999;
    border-right: 1px solid #eee;
    border-bottom: 1px solid #eee;
}