Stage 5 of the Rapid Mathematics track — the capstone: seven trials where the identities of algebra become mental shortcuts. Difference of squares, squaring near a base, the same-tens trick, base-100 products, and the general cross-multiply that ties it all together. No paper.
Each trial is locked until you clear the one before it. Every level scores out of 1000 — 600 for accuracy, 400 for speed — so speed alone can't clear the bar; you have to solve most problems, and quickly. Reach 650 to unlock the next.
You can turn a product into an algebraic identity on sight — straddle a round number, anchor a square to its base, work from 100, or cross-multiply anything. That's the whole Rapid Mathematics ladder, from place value to algebra, all in your head.