Stage 1 of the Rapid Mathematics track: seven trials in the two habits every fast mental calculator is built on — place value and complements — escalating until you're splitting, bonding, bridging, checking, and doing it all from memory. 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 pull a number apart by place value and snap numbers up to the next ten and hundred — and tell, on sight, which one a problem needs.