id: colour_mixer
order: 100
attributes: [colour]
rust: ColourMixer

why_rust: |
  Thirty-six parameters — twelve hue bands times hue, saturation and
  luminance — generated as a grid, each carrying a `Facet` naming its band and
  the band's centre on the hue wheel. Spelling that out as thirty-six YAML
  entries would be a worse description than the loop that produces it, and the
  band centres are computed rather than listed.

placement: |
  Last. It is the finishing control, and it should act on the tones the user
  has already settled.