@media (orientation: landscape) {
    .left-container {
        flex: 0 1 20%;
        min-height: auto;
    }

    #main {
        flex: 1 0 60%;
    }

    #main > h1 {
        font-size: 2.5em;
    }

    .right-container {
        flex: 0 1 20%;
    }
}