/* --------------------- */
/* Index / Layout        */
/* --------------------- */
html,
body {
    height: 100%;
    margin: 0;
    background: #000080;
    /* dunkelblau */
    display: flex;
    flex-direction: column;
    color: yellow;
    font-family: Arial, sans-serif;
}

/* --------------------- */
/* Header                */
/* --------------------- */
header {
    height: 125px;
    text-align: center;
    background-color: #000080;
    color: white;
    padding: 20px 0;
}

/* --------------------- */
/* Unterer Bereich       */
/* --------------------- */
main {
    flex: 1;
    display: flex;
    flex-direction: row;
}

/* Linke Spalte / Menü */
nav {
    width: 170px;
    height: 100%;
    background-color: #000080;
    box-sizing: border-box;
    padding: 5px;
}

/* Rechte Spalte / Hauptinhalt */
section {
    flex: 1;
}

/* --------------------- */
/* Iframes immer voll    */
/* --------------------- */
iframe {
    width: 100%;
    height: 100%;
    border: none;
    display: block;
}

/* --------------------- */
/* Trennlinien           */
/* --------------------- */
.line-horizontal {
    height: 4px;
    background: white;
    width: 100%;
}

.line-vertical {
    width: 4px;
    background: white;
    height: 100%;
}

/* --------------------- */
/* Menü-Links & Bild     */
/* --------------------- */
nav a {
    display: block;
    margin: 6px 0;
    font-family: Arial, sans-serif;
    font-size: 14px;
    font-weight: bold;
    text-decoration: none;
    color: white;
}

nav a:visited {
    color: yellow;
}

nav a:active {
    color: red;
}

nav a:hover {
    color: yellow;
    text-decoration: underline;
}

nav img {
    display: block;
    margin: 10px auto;
    max-width: 100%;
    max-height: 20px;
    width: auto;
    height: auto;
}

/* --------------------- */
/* Responsive            */
/* --------------------- */
@media (max-width: 600px) {
    main {
        flex-direction: column;
    }

    nav,
    section {
        width: 100%;
        height: 50%;
    }

    .line-vertical {
        display: none;
    }
}