.grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 10px;
}

.cell {
    background-color: deepskyblue;
    color: white;
    padding: 30px;
}

header {
    grid-column-end: span 3;
    height: 300px;
}

nav {
    grid-column-end: span 3;
}

section {
    grid-column-end: span 2;
}

article {
    grid-column-end: span 2;
}

aside {
    grid-row-end: span 2;
}

footer {
    grid-column-end: span 3;
}