Every explanation, checked before you see it.

How we verify every explanation

1. 1

   Written, not improvised

   Each explanation is authored with the full worked solution and a reason every wrong answer is wrong — not generated on the fly the moment you click, where mistakes slip through unseen.

2. 2

   Independently checked

   Our questions and explanations are written with AI, so the check is done by a separate AI model. It works the problem out for itself, then compares its answer with ours and audits the arithmetic, the logic, and every distractor rationale. Agreement is the bar — not a single model’s first guess. No person reviews every question; a person reviews every question a student reports.

3. 3

   Fail closed

   If an explanation does not pass that check, it is pulled. You never see an explanation that failed review — the question falls back to a plain answer key until we fix it. We would rather show less than show something wrong.

Found a mistake? We fix it.

We’re not perfect, and we don’t pretend to be. You can report any question from inside the app, and a real person reviews every report. If something’s wrong, we fix it — and re-run it through the same verification. That feedback loop is exactly the part the generate-it-live tools skip.

Where we are today

Counted from the bank as this page loaded, not typed in by hand: 5,934 of the 5,936 questions in rotation carry a written explanation. Anything still in review shows a plain, correct answer key in the meantime — never an unverified walkthrough dressed up as one.

Taking questions out matters as much as putting them in. We have retired 1,806 items that were once in the bank:

• Duplicate or near-duplicate of another question618
• Outside the tested syllabus52
• Answer-pattern bias removed21
• Rewritten, and the old version replaced8
• Another recorded reason47
• Retired before we recorded a reason1,060

That last row is the honest part: our earliest cleanups did not record a reason, so we can tell you those questions are gone but not, from the data alone, why. Everything retired since does.