html, body {
    margin: 0;
    padding: 0;
}

:root { 
    --white: #fff;
    --red: #FF0002;
}

.flag {
    background: var(--red);
    width: 200px;
    height: 200px;
    position: absolute;
    /* centering: */
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
}

.cross1 {
    background: var(--white);
    width: 35px;
    height: 135px;
    position: absolute;
    /* centering: */
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
}

.cross2 {
    background: var(--white);
    width: 135px;
    height: 35px;
    position: absolute;
    /* centering: */
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
}