body {
    display: flex;
    flex-wrap: wrap;
    height: 100vh;
    margin: 0;
}

.block {
    flex: 1 1 25%;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 24px;
    color: white;
}

.center {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    text-align: center;
}