/* Keep header unchanged */
.header {
    max-width: 1200px;
    margin: 0 auto;
}

/* Extend sections below header by 50% */
div.region-content {
    max-width: none !important;   /* remove parent container width restriction */
    width: 100% !important;       /* full width */
    padding-left: 0 !important;   /* remove default OJS padding */
    padding-right: 0 !important;
}

div.region-content > div.section {
    width: 150%;                   /* 50% wider than default */
    margin-left: -25%;             /* shift left to center */
    margin-right: -25%;            /* shift right equally */
    padding-left: 40px;            /* keep internal padding */
    padding-right: 40px;
    box-sizing: border-box;
}