HTML details and summary
Create disclosure panels without custom JavaScript.
What this solves
Hide advanced assumptions until a user needs them. This pattern is useful when the business question is clear but a generic tutorial is too abstract.
The rule
Place a summary as the first child of details.
<details><summary>Advanced options</summary><p>...</p></details>Real-work checklist
- Define the business key and expected grain before writing the formula, query or markup.
- Test the pattern on a small known sample where you can verify the answer manually.
- Check missing values, duplicates and data types before trusting a large result.
- Scale to the real file or database only after the logic is proven.
Common mistake
Do not hide critical information users must see to use a tool correctly.