An optional open-or-not section per lesson with a fun fact, something humorous, or maths in the news - a low-pressure reason to stay on the page. Constraint: self-hosted content only, never an external link (same reasoning as self-hosting fonts - no third-party calls, nothing leaks).
From NOTES/2026-07-22-design-decisions.md (section 3).
An optional open-or-not section per lesson with a fun fact, something humorous, or maths in the news - a low-pressure reason to stay on the page. Constraint: self-hosted content only, never an external link (same reasoning as self-hosting fonts - no third-party calls, nothing leaks).
From NOTES/2026-07-22-design-decisions.md (section 3).