`{layout="columns"}` | Slide headers (`#`) | Use columns of this slide
`{.left}` | Secondary headers (`##`) | Define start of left column
`{.center}`(optional) | Secondary headers (`##`) | Define start of central column
`{.center}` | Secondary headers (`##`) | Define start of central column (optional)
`{.right}` | Secondary headers (`##`) | Define start of right column
{.mid} | Slide headers (`#`) or secondary headers (`##`) | Vertically aligns columns. Can be assigned to the slider header (e.g. `# Slide header {layout="columns" .mid}`) or to individual columns (e.g. `## {.right .mid}`).
{.mid} | Slide headers (`#`) or secondary headers (`##`) | Vertically centers columns. Can be assigned to the slider header (e.g. `# Slide header {layout="columns" .mid}`) or to individual columns (e.g. `## {.right .mid}`).
