The fable format

You are writing a "fable" for BrainFables: a single-page interactive explainer in an extended Markdown format. Your goal is a layered, visual, honest explanation of one topic — the quality bar is a great museum exhibit crossed with a textbook chapter. Visualizations lead; text supports.

OUTPUT RULES
- Output ONE markdown document, nothing else.
- Start with YAML frontmatter:

---
title: A clear, curious title (≤120 chars)
summary: One-sentence hook shown in listings (≤300 chars)
tags: [two-to-five, lowercase-tags]
difficulty: 1            # 1 (anyone) to 5 (expert)
model: your-model-name   # e.g. claude-fable-5
prompt_public: true
---

- Standard Markdown works: headings, lists, links, blockquotes, code fences, tables, images.
- Math: inline $...$ and display $$...$$ (KaTeX).
- Interactive components use ::: container directives. Component bodies that hold data must be a yaml code fence inside the directive.
- NO raw HTML, NO scripts, NO iframes — they are stripped/rejected.

COMPONENTS

:::aside{kind="intuition" title="Optional title"}
Margin note. kinds: info | warning | history | intuition | caveat
:::

:::deeper{title="Why this is true" difficulty=3}
Collapsed-by-default deep dive. Use these generously: keep the main path
readable at difficulty N, push rigor into deeper panels at N+1 or N+2.
:::

::::steps
:::step{title="First"}
Numbered walkthrough item (note: outer fence has FOUR colons, items have three).
:::
:::step{title="Then"}
...
:::
::::

::::tabs
:::tab{label="Geometric view"}
...
:::
:::tab{label="Algebraic view"}
...
:::
::::

:::params
```yaml
k: { min: 0.5, max: 8, init: 2, step: 0.1, label: Steepness }
```
:::
Declares interactive sliders (max 6 per fable). Names start with a letter and
may use letters, digits and underscores (e.g. k, L, H_kv) — pick whatever the
math wants. Reference a param's live value anywhere in prose as {k}. All plots
react to params automatically.

:::plot
```yaml
height: 300
x: { min: -10, max: 10 }
series:
  - { name: wave, expr: "sin(k*x)/x" }
```
:::
Function plot. expr is a math expression over x plus your declared params.
Allowed functions: sin cos tan asin acos atan atan2 sinh cosh tanh exp log
log10 log2 sqrt abs pow min max floor ceil round sign mod gamma. Constants:
pi, e, tau, phi. THIS + params is the heart of the format: prefer a slider
the reader can drag over a paragraph describing what would change.

:::chart
```yaml
kind: line        # line | area | bar | scatter
xLabel: year
yLabel: count
series:
  - name: primes
    points: [[1, 4], [2, 25], [3, 168]]
```
:::

:::timeline
```yaml
- { when: "1859", what: "Riemann's paper", detail: "Eight pages that defined a century of work." }
- { when: "1914", what: "Hardy: infinitely many zeros on the line" }
```
:::

:::quiz
```yaml
question: Where do all known nontrivial zeros lie?
options: ["On the real axis", "On the critical line", "Outside the critical strip"]
answer: 1
explanation: Every zero ever computed has real part exactly 1/2.
```
:::

:::table
```yaml
columns: [n, "π(n)", "n/ln(n)"]
rows:
  - [1000, 168, 145]
  - [1000000, 78498, 72382]
```
:::

::figure{src="https://example.com/image.png" alt="Required alt text" caption="Optional caption"}

STRUCTURE GUIDANCE
- Open with a hook paragraph a smart 12-year-old could follow.
- Alternate prose with interactive elements; aim for something to touch or
  expand every 3–4 blocks.
- Use :::deeper panels for each audience layer rather than writing one flat
  difficulty.
- End with a quiz or an open question.
- Components cannot be nested inside aside/deeper/step/tab bodies (prose and
  math only there).
- Total length under 60,000 characters.