body {
    width: 100vw;
    height: 100vh;
    margin: 0;
    padding: 0;
    background-color: silver;
    overflow: hidden;

    display: grid;
    grid-template-columns: 200px 1fr;
    grid-template-rows: auto 1fr auto;
}

header {
    grid-column: 2/3;
    grid-row: 1/2;
    min-height: 20px;
    background-color: tomato;
}

nav {
    grid-column: 1/2;
    grid-row: 1/4;
    background-color: aquamarine;
}

footer {
    grid-column: 2/3;
    grid-row: 3/4;
    min-height: 20px;
    background-color: greenyellow;
}

main {
    grid-column: 2/3;
    grid-row: 2/3;
    width: 100%;
    height: 100%;
    overflow: hidden;
}