Denksleutel

Tony Ryan's thinking keys (denksleutels): short tasks that make a pupil
think differently, like "name eight things you would never find in a Roman
fort". There is no right answer: the pupil comes up with as many ideas as
they can, and the teacher judges them on fluency, flexibility and
originality. Works for any subject: the content comes from the task.

Write the task itself in the task's `prompt`. The field adds two things:

- **In the booklet**, a card with the key's number, its name and a
  one-line explanation (`explanation: false` leaves the explanation out),
  plus what the key gives the pupil to think about.
- **On the answer sheet**, a form that fits the key.

| `key` | Answer sheet | Needs |
| --- | --- | --- |
| `reverse`, `what-if`, `variations`, `prediction`, `different-uses`, `ridiculous`, `brainstorming`, `alternatives`, `interpretation` | `count` numbered lines | |
| `commonality`, `forced-relationships` | `count` numbered lines | `things`: two things |
| `question` | `count` numbered lines | `answer`: the answer, printed big |
| `brick-wall` | `count` numbered lines | `wall`: what seems impossible, printed on a brick wall |
| `picture` | `count` numbered lines | a strange drawing of lines and a circle; `picture` picks another one |
| `disadvantages` | `count` rows: disadvantage, and how to fix it | |
| `alphabet` | a line per letter, A to Z or `letters` | |
| `bar` | bigger, add, replace (groter maken, iets toevoegen, iets vervangen), and a drawing box (`drawing: false` leaves it out) | |
| `combination` | the features of each thing, a drawing and an explanation | `things`: two things |
| `inventions` | a drawing and an explanation | |
| `construction` | a drawing and an explanation | `materials`: the only materials allowed |

`count` (3 to 12) defaults to 5 to 10 by key; more than 6 go in two
columns. A setting that doesn't belong to the key is an error, and so is a
key without what it needs.

`examples` are example answers for the teacher. They go into the model
answer and the answer key, never to the pupil: in list order, one per
letter for `alphabet` (matched by first letter), bigger, add and replace
for `bar`, the explanation for the drawing keys. For `disadvantages` they
are the disadvantages, with a matching solution per disadvantage in
`solutions`.

Not graded automatically: every area goes to the teacher.

```yaml
- type: task
  id: q5
  prompt: Noem acht dingen die je **nooit** in een Romeins fort zou vinden.
  answer:
    type: tempono/thinking-keys@1.0.0
    key: reverse
    examples: [Een stopcontact, Een trampoline]
```