extends: metric
message: "Make your content readable. Set a Flesch–Kincaid grade level (%s) below 10. To lower the score, use shorter sentences and more common words."
link: https://en.wikipedia.org/wiki/Flesch%E2%80%93Kincaid_readability_tests

formula: |
  (0.39 * (words / sentences)) + (11.8 * (syllables / words)) - 15.59

condition: "> 1"