* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

.wrapper {
    display: flex;
    flex-flow: row wrap;
    font-weight: bold;
    text-align: center;
    font-family: Arial, sans-serif;
}

.wrapper > * {
    padding: 20px;
    flex: 1 100%;
}

.header-flex-2 {
    background: tomato;
    order: 0;
}

.footer-flex-2 {
    background: lightgreen;
    order: 5;
}

.main {
    text-align: left;
    background: deepskyblue;
    min-height: 200px;
    order: 2;
}

.aside {
    min-height: 150px;
}

.aside-1 {
    background: gold;
    order: 3;
}

.aside-2 {
    background: hotpink;
    order: 4;
}

/* Responsive cho Tablet (>= 600px): 2 cột ở phần Aside */
@media (min-width: 600px) {
    .aside-1 {
        flex: 1 50%;
    }

    .aside-2 {
        flex: 1 50%;
    }
}

/* Responsive cho Desktop (>= 1200px): 3 cột (Aside 1 | Main | Aside 2) */
@media (min-width: 1200px) {
    .main {
        flex: 3 0px;
        order: 2;
        height: 400px;
    }

    .aside-1 {
        flex: 1 0px;
        order: 1;
        height: 400px;
    }

    .aside-2 {
        flex: 1 0px;
        order: 3;
        height: 400px;
    }
}