html {
    height: 100%;
}

body {
    background-color: #444;
    background-image: url("background.png");
    margin: 0;
    height: 100%;
}

#outerwrapper {
    display: table;
    table-layout: fixed;
    /*makes IE obey width*/
    height: 100%;
    width: 80%;
    margin-left: 10%;
}

#innerwrapper {
    display: table-cell;
    vertical-align: middle;
}

#container {
    display: flex;
    flex-flow: row wrap;
    justify-content: center;
}

.tile a {
    display: flex;
    margin: 1em;
}

.tile img {
    width: 10em;
    height: 10em;
    border-radius: 0.75em;
}