.container {
    display: grid;

    grid-template-areas:
            "header header header"
            "nav content side"
            "footer footer footer";

    grid-template-columns: 200px 1fr 200px;
    grid-template-rows: auto 1fr auto;
    grid-gap: 10px;

    height: 100vh;
}

header {
    grid-area: header;
}

nav {
    grid-area: nav;
    margin-left: 0.5rem;
}

main {
    grid-area: content;
}

aside {
    grid-area: side;
    margin-right: 0.5rem;
}

footer {
    grid-area: footer;
}

.ul_3collist {
    -webkit-column-count: 3; /* Chrome, Safari, Opera */
    -moz-column-count: 3; /* Firefox */
    column-count: 3;
}
.ul_5collist {
    -webkit-column-count: 5; /* Chrome, Safari, Opera */
    -moz-column-count: 5; /* Firefox */
    column-count: 5;
}
.li_collist {
    /* display: inline-block; */
}

@media (max-width: 768px) {
    .container {
        grid-template-areas:
                "header"
                "nav"
                "content"
                "side"
                "footer";

        grid-template-columns: 1fr;
        grid-template-rows:
                auto /* Header */
                minmax(75px, auto) /* Nav */
                1fr /* Content */
                minmax(75px, auto) /* Sidebar */
                auto; /* Footer */
    }

    nav, aside {
        margin: 0;
    }
}