#p1 {
    column-span: 4;
}
#p2 {
    column-span: 3;
}
#p3 {
    column-span: 1;  /* Didn't need to be set explicitly. */
}
#p4 {
    column-span: 2;
}
#p5 {
    column-span: 2;
}
#p6 {
    /* Default value is 1. */
}
#p7 {
    column-span: 3;
}

Grid {
    grid-size: 4 4;
    grid-gutter: 1 2;
}

Placeholder {
    height: 100%;
}