.vertical-center {
    min-height: 100%;  /* Fallback for browsers do NOT support vh unit */
    min-height: 100vh; /* These two lines are counted as one :-)       */

    display: flex;
    align-items: center;
}

.horizontal-center {
    margin: 0 auto;
}

.fullsize {
    width: 100%;
    height: 100%;
}