Rigorous notes, interactive visualisers and instant-feedback quizzes for CAIE 9231 — quietly reorganising around the exact topics you find hard.
Most revision sites are notes with a quiz bolted on. This is built around the specific things that separate a B from an A* in 9231.
Every visualiser works the answer out twice — once from the formula in the notes, once by brute force — and only shows a tick when the two agree. Nothing here is asserted without evidence.
Written against the official 2026–27 subject content, including its limits: eigenvalues real and distinct, matrices to 3×3, polar curves with r ⩾ 0. No padding from other boards.
Add it to your home screen and the whole pack — all 13 topics, every visualiser — keeps working on a bus, on a plane, or on school wifi that has given up.
The diagnostic and the ⚑ flags push your weak topics to the top of this page. Free, no sign-up, and nothing you do is sent anywhere.
Fifteen minutes to find your gaps, then work them down one at a time.
One question per topic, about five minutes. Answer honestly — there is a “not sure” button, and using it is more useful than guessing.
Anything wrong or skipped becomes a focus area at the top of this page. You can also flag a topic yourself with the ⚑ on its card.
Read the worked examples, push the visualiser around until the idea clicks, then take the quiz. Mark the topic complete and your streak keeps going.