.container {
    height: 100%;
    display: grid;
    grid-gap: 3px;
    grid-template-columns: repeat(12, 1fr);
    grid-template-rows: 40px auto 40px;
    grid-template-areas: 
        "h h h h h h h h h h h h"
        "c c c c c c c c c c c c"
        "f f f f f f f f f f f f";
}

.header {
    grid-area: h;
}



.content {
    grid-area: c;
}

.footer {
    grid-area: f;
}