div.session-parallel {
    /*background-color: transparent;*/
    background-color: #DDDDDD;
    color: #333;
    margin-top: 3ex;
    margin-bottom: 3ex;         
}

div.session-parallel-flex {
    display: flex;
    flex-direction: row;
    flex-wrap: nowrap;
    justify-content: flex-start; /* center */    
    column-gap: 3ex;
}

div.session-parallel-flex > div.session {
    flex-grow: 1;
    flex-shrink: 0;
    flex-basis: 0;
}


div.session-parallel-flex > div.slot-title {
    display: block;
}