.app {
    display: flex;
    flex-direction: column;
    width: 100%;
    height: 100%;
    margin: 0;
}

    .app main {
        display: flex;
        flex: 1 0 100%;
        /*background: #fdf8ec;*/
    }
    .app.inverted main {
        background: #333;
        color: #fff;
    }