Engineering
5 posts on this topic.
8 October 2026 · 8 min read
Stripe Checkout without webhooks: a pull-based design
How we confirm Stripe Checkout payments with no webhook: session reuse, a unique checkout key, strict verification and a 10-minute reconciliation sweep.
7 October 2026 · 7 min read
What actually makes a maze hard (we measured it)
Size is not difficulty. We graded a maze generator easy to evil, measured every page, and found one of our three difficulty signals ran backwards.
1 October 2026 · 8 min read
How we make sure every sudoku has one solution
How our sudoku generator works: fill a grid, remove clues in pairs, and re-solve after every removal so each board has one answer. Real code and timings.
31 August 2026 · 6 min read
The cast and the sets: the art that holds a book together
The hero’s face is the famous consistency problem. The friend, the teacher and every classroom are the harder one. Here’s the reference art behind it.
18 August 2026 · 5 min read
The four locks behind a consistent AI picture book
Character consistency across a whole book isn’t a prompt trick. It takes four specific locks, and here’s what each one does and why it matters.