Flexbox does not display text in columns
<p>I want three articles to be displayed on the homepage of the desktop version, each article in its own column. As I'm using flexbox this should be done easily, as I read in some tutorials. </p>

<p>But nothing changes, the articles are still one under another. I tried with this tutorial: <a href="https://davidwalsh.name/flexbox-column" rel="nofollow noreferrer">https://davidwalsh.name/flexbox-column</a></p>

<p>HTML</p>

<pre><code>&lt;!DOCTYPE html&gt;
&lt;html&gt;

&lt;head&gt;
    &lt;title&gt;Munchies&lt;/title&gt;
    &lt;meta name="viewport" content="width=device-width, initial-scale=1"&gt;
    &lt;link rel="stylesheet" href="css/style3.css"&gt;
&lt;/head&gt;

&lt;body&gt;
    &lt;nav&gt;
        &lt;ul class="navigation"&gt;
            &lt;li class="nav-item"&gt;&lt;a href="index.html"&gt;Home&lt;/a&gt;&lt;/li&gt;
            &lt;li class="nav-item"&gt;&lt;a href="world.html"&gt;Around the globe&lt;/a&gt;&lt;/li&gt;
            &lt;li class="nav-item"&gt;&lt;a href="where.html"&gt;Where to eat?&lt;/a&gt;&lt;/li&gt;
            &lt;li class="nav-item"&gt;&lt;a href="recipes.html"&gt;Recipes&lt;/a&gt;&lt;/li&gt;
            &lt;li class="nav-item"&gt;&lt;a href="about.html"&gt;About me&lt;/a&gt;&lt;/li&gt;
        &lt;/ul&gt;
    &lt;/nav&gt;
    &lt;input type="checkbox" id="nav-trigger" class="nav-trigger" /&gt;
    &lt;label for="nav-trigger"&gt;&lt;/label&gt;
    &lt;div class="wrapper"&gt;
        &lt;div class="main-content"&gt;

            &lt;article&gt;
                &lt;h3&gt;Featured:&lt;/h3&gt;
                &lt;h2 id="brussels"&gt;Brussels&lt;/h2&gt;

                &lt;h3&gt;Belgian Food&lt;/h3&gt;
                &lt;p&gt;
                    Traditional Belgian food is not for the faint hearted, with dishes such as bloedworst (black pudding made from pig&amp;#39;s blood, served with apple sauce), breugel kop (chunks of beef and tongue set in gelatine) and paar de filet/steack de cheval (horse
                    steak). But there are more elegant spins on the local fare available: try La Maison du Cygne, which fuses Belgian and French cuisine and also offers glorious views of Brussels&amp;#39; gabled, gilded Grand Place.
                &lt;/p&gt;
            &lt;/article&gt;

            &lt;article&gt;
                &lt;h3&gt;Featured:&lt;/h3&gt;
                &lt;h2&gt;Real guacamole&lt;/h2&gt;
                &lt;h3&gt;Ingredients:&lt;/h3&gt;
                &lt;ul class="recipe"&gt;
                    &lt;li&gt;4 mild chillies, finely chopped&lt;/li&gt;
                    &lt;li&gt;bunch coriander, chopped&lt;/li&gt;
                    &lt;li&gt;2 tomatoes, finely chopped&lt;/li&gt;
                    &lt;li&gt;salt, to taste&lt;/li&gt;
                    &lt;li&gt;1 onion, finely chopped&lt;/li&gt;
                    &lt;li&gt;&amp;#189; lime, juice only&lt;/li&gt;
                    &lt;li&gt;3 ripe avocados&lt;/li&gt;
                &lt;/ul&gt;

                &lt;h3&gt;Directions:&lt;/h3&gt;
                &lt;p&gt;
                    In a pestle and mortar, pound the chillies, coriander, tomatoes, salt and onion to a fine paste.
                &lt;/p&gt;
                &lt;p&gt;
                    Add a little water and lime juice to make a looser mixture. Mash in the avocados. Serve.
                &lt;/p&gt;
            &lt;/article&gt;

            &lt;article&gt;
                &lt;h3&gt;Featured:&lt;/h3&gt;
                &lt;h2 id="belgium"&gt;Belgium&lt;/h2&gt;

                &lt;h3&gt;Waffles&lt;/h3&gt;
                &lt;p&gt;
                    Belgian waffles (gauffres) are internationally known, but in Belgium there are two different types: the Brussels waffle and the Li&amp;#232;ge waffle. The Brussels waffle is rectangular, golden brown on the outside, dusted with powdered/icing sugar and then
                    sometimes covered with syrup, slices of fruit, chocolate spread and whipped cream &amp;#45; all of which is deemed a mite inauthentic by waffle connoisseurs! The denser textured Liege waffle is square and has burnt sugar on the outside. They are sold
                    by street vendors and gourmet restaurants alike, all over Belgium.
                &lt;/p&gt;
            &lt;/article&gt;
        &lt;/div&gt;
        &lt;aside class="aside aside-2"&gt;
            MUNCHIES
        &lt;/aside&gt;
    &lt;/div&gt;
&lt;/body&gt;

&lt;/html&gt;
</code></pre>

<p>CSS
        /<em>CSS reset</em>/</p>

<pre><code>        html, body, div, span, applet, object, iframe,
        h1, h2, h3, h4, h5, h6, p, blockquote, pre,
        a, abbr, acronym, address, big, cite, code,
        del, dfn, em, img, ins, kbd, q, s, samp,
        small, strike, strong, sub, sup, tt, var,
        b, u, i, center,
        dl, dt, dd, ol, ul, li,
        fieldset, form, label, legend,
        table, caption, tbody, tfoot, thead, tr, th, td,
        article, aside, canvas, details, embed,
        figure, figcaption, footer, header, hgroup,
        menu, nav, output, ruby, section, summary,
        time, mark, audio, video {
            margin: 0;
            padding: 0;
            border: 0;
            font-size: 100%;
            font: inherit;
            vertical-align: baseline;
        }
    /* Site wrapper, using flexbox*/

    .wrapper {
          display: -webkit-box;
        display: -moz-box;
        display: -ms-flexbox;
        display: -webkit-flex;
        display: flex;
        -webkit-flex-flow: row wrap;
        flex-flow: row wrap;
        text-align: center;
        flex: 1 100%;
        min-height: 100%;
        min-width: 100%;
        background-color: rgb(237, 237, 237);
        position: relative;
        top: 0;
        bottom: 100%;
        left: 0;
        z-index: 1;
        padding: 0em;
        background-size: 200%;
    }

    .main {
        padding: 1em;
        flex: 1 100%;
        text-align: justify;
        background: rgb(237, 237, 237);
        order: 3;
        font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
        font-size: 18px;
        line-height: 1.3;
    }

    .aside-1 {
        padding-top: 1em;
        padding-left: 5em;
        padding-right: 5em;
        padding-bottom: 1em;
        margin-top: 0em;
        flex: 1 100%;
        background: rgb(224, 224, 224);
        order: 2;
    }

    .aside-2 {
        padding: 10px;
        margin-top: 0em;
        flex: 1 100%;
        background: rgb(55, 60, 57);
        order: 1;
        font-family: Impact, sans-serif;
        font-size: 50px;
        color: white;
    }
    /*Navigation menu*/

    .navigation {
        width: 100%;
        height: 100%;
        position: fixed;
        top: 0;
        right: 0;
        bottom: 0;
        left: 0;
        z-index: 0;
        list-style: none;
        background: rgb(35, 36, 35);
    }
    /*List items width in navigation menu*/

    .nav-item {
        width: 200px;
        border-top: 1px solid rgb(73, 70, 70);
        border-bottom: 1px solid rgb(73, 70, 70);
    }
    /*Appearance for navigation menu links*/

    .nav-item a {
        display: block;
        padding: 1em;
        background: rgb(35, 36, 35);
        color: white;
        font-size: 1.2em;
        text-decoration: none;
        transition: background 0.5s;
    }
    /*Changing the color of the link when hovering over with the cursor*/

    .nav-item a:hover {
        background: black;
    }
    /*Navigation trigger*/

    .nav-trigger {
        /*hide the checkbox input*/
        position: absolute;
        clip: rect(0, 0, 0, 0);
    }

    label[for="nav-trigger"] {
        /*critical positioning styles */
        position: fixed;
        left: 15px;
        top: 15px;
        z-index: 2;
        /*styles */
        height: 30px;
        width: 30px;
        cursor: pointer;
        background-image: url("data:image/svg+xml;utf8,&lt;svg xmlns='http://www.w3.org/2000/svg' xmlns:xlink='http://www.w3.org/1999/xlink' version='1.1' x='0px' y='0px' width='30px' height='30px' viewBox='0 0 30 30' enable-background='new 0 0 30 30' xml:space='preserve'&gt;&lt;rect width='30' height='6'/&gt;&lt;rect y='24' width='30' height='6'/&gt;&lt;rect y='12' width='30' height='6'/&gt;&lt;/svg&gt;");
        background-size: contain;
    }

    .nav-trigger+label, .wrapper {
        transition: left 0.3s;
    }

    .nav-trigger:checked+label {
        left: 215px;
    }

    .nav-trigger:checked~.wrapper {
        left: 200px;
    }

    .responsive-image {
        max-width: 100%;
    }

    html, body {
        height: 100%;
    }

    body {
        /*Without this, the body has excess horizontal scroll when the menu is open*/
        overflow-x: hidden;
        margin-left: 0px;
        margin-right: 0px;
        font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
        font-size: 14px;
    }



    /*Styles for table of content*/

    .content {
        list-style-type: none;
        text-align: center;
        font-size: 18px;
        max-width: 15em;
        margin: auto;
    }

    .content li a {
        display: block;
        padding: 0.7em;
        background: rgb(35, 36, 35);
        /*SPREMENI BARVO TEKSTA, ISTO KOT OZADJE*/
        color: white;
        font-size: 1em;
        text-decoration: none;
        transition: background 0.5s;
        /*SPREMENI BARVO BORDERJA, ISTO KOT OZADJE*/
        border-top: 1px solid white;
        border-bottom: 1px solid white;
                border-radius: 10px;
    }

    .content a:hover {
        background: black;
    }

    .profile-pic {
        border-radius: 50%;
        max-width: 30%;
        max-height: 30%;
        float: left;
        margin: 1em 1em 1em 1em;
    }

    #social img {
        display: inline-block;
        max-height: 50px;
        max-width: 50px;
        margin: 1em 1em 1em 1em;
        float: left;
    }

    .anchor:before {
        content: "";
        display: block;
        height: 50px;
        /* fixed header height*/
        margin: -50px 0 0;
        /* negative fixed header height */
    }

    .index-img {
        max-width: 70%;
        border-radius: 25px;
        display: block;
        margin: auto;
        padding: 10px;
    }

        .recipe {
      list-style: none;
    }
    /*Tablets responsive*/

    @media all and (min-width: 700px) {
        /* Navigation Menu - Background */
        .navigation {
            /* critical sizing and position styles */
            height: 6em;
            z-index: 2;
            overflow: hidden;
            /* non-critical appearance styles */
            background: rgb(55, 60, 57);
        }
        /* Navigation Menu - List items */
        .nav-item {
            /* non-critical appearance styles */
            width: 20%;
            height: 6em;
            border-top: none;
            border-bottom: none;
            float: left;
        }
        .nav-item a {
            /* non-critical appearance styles */
            width: auto;
            height: 6em;
            background: rgb(55, 60, 57);
            font-size: 1em;
            transition: color 0.2s, background 0.5s;
            text-align: center;
            padding-top: 2.3em;
            border-left: 1px solid rgb(73, 70, 70);
            border-right: 1px solid rgb(73, 70, 70);
        }
        /* Nav Trigger */
        .nav-trigger {
            display: none;
        }
        label[for="nav-trigger"] {
            /* critical positioning styles */
            display: none;
        }
        .nav-trigger+label, .wrapper {
            transition: none;
        }
        .nav-trigger:checked+label {
            left: 0;
        }
        .nav-trigger:checked~.wrapper {
            left: 0px;
        }
        .main {
            padding: 10px;
            flex: 1 100%;
        }

        .recipe {

        }
        .aside-1 {
            padding: 10px;
            flex: 1 100%;
            font-size: 18px;
            /*position: fixed;*/
            height: 100%;
        }
        .aside-2 {
            background: red;
            margin-top: 1.5em;
            flex: 0 0 100%;
        }
        body {
            margin-top: 0em;
        }
        .responsive-image {
            margin: auto;
            padding: 20px;
            display: block;
            width: 40%;
        }
        /*Styles for table of content*/
        .content {
            list-style-type: none;
            text-align: center;
            font-size: 18px;
        }
        .content li a {
            display: block;
            padding: 0.7em;
            background: rgb(55, 60, 57);
            /*SPREMENI BARVO TEKSTA, ISTO KOT OZADJE*/
            color: white;
            font-size: 1em;
            text-decoration: none;
            transition: background 0.5s;
            /*SPREMENI BARVO BORDERJA, ISTO KOT OZADJE*/
            border-top: 1px solid rgb(237, 237, 237);
            border-bottom: 1px solid rgb(237, 237, 237);
        }
        .index-img {
            max-width: 50%;
        }
    }
    /*Desktop responsive*/

    @media all and (min-width: 900px) {
        /* Navigation Menu - Background */
        .navigation {
            /* critical sizing and position styles */
            height: 3em;
            z-index: 2;
            overflow: hidden;
            /* non-critical appearance styles */
            background: rgb(55, 60, 57);
        }
        /* Navigation Menu - List items */
        .nav-item {
            /* non-critical appearance styles */
            width: auto;
            height: 3em;
            border-top: none;
            border-bottom: none;
            float: left;
        }
        .nav-item a {
            /* non-critical appearance styles */
            width: auto;
            height: 3em;
            background: rgb(55, 60, 57);
            font-size: 1em;
            transition: color 0.2s, background 0.5s;
            padding: 1em;
        }
        /* Nav Trigger */
        .nav-trigger {
            display: none;
        }
        label[for="nav-trigger"] {
            /* critical positioning styles */
            display: none;
        }
        .nav-trigger+label, .wrapper {
            transition: none;
        }
        .nav-trigger:checked+label {
            left: 0;
        }
        .nav-trigger:checked~.wrapper {
            left: 0px;
        }
        .main {
            padding: 10px;
            flex: 1 60%;
        }

        .aside-1 {
            padding: 10px;
            font-size: 18px;
            flex: 0 0 200px;
            height: auto;
        }
        .aside-2 {
            background: white;
            margin-top: 0;
            color: black;
            flex: 0 0 100%;
        }
        body {
            margin-top: 3em;
        }

        /*.responsive-image {
            margin: auto;
            padding: 20px;
            display: block;
            width: 40%;
        }*/
        /*Styles for table of content*/
        .content {
            list-style-type: none;
            text-align: center;
            font-size: 18px;
            max-width: 10em;
            /*margin-top: 6em;*
            /*position: fixed;
            left: 4em;*/
                        padding: 1em;
        }
        .content li a {
            display: block;
            padding: 0.7em;
            background: rgb(55, 60, 57);
            color: white;
            font-size: 1em;
            text-decoration: none;
            transition: background 0.5s;
            border-top: 1px solid rgb(237, 237, 237);
            border-bottom: 1px solid rgb(237, 237, 237);
        }
        .index-img {
            max-width: 31%;
            display: block;
            margin: auto;
        }
        .recipe {

        }
                .content-wrapper{
                        position: fixed;
                }

                .main-content{
                    order: 2;
                }

                .main-content &gt; article {
                    width: 30%;
                    padding: 10px;
                    order: 2;
                }
    }
</code></pre>

<p><a href="https://jsbin.com/kakiqanaho/edit?output" rel="nofollow noreferrer">https://jsbin.com/kakiqanaho/edit?output</a>
 Thanks for the help!</p>