I'm a developer in New Jersey. About a year ago my daughter, who was in third grade, was hitting the wall on basic math facts. She knew the strategies. She could derive an answer. But the recall was slow enough that anything that depended on the fact, word problems, division, fractions, was eating up all her working memory and crashing the rest of the problem. I tried the apps everyone tries. Xtramath, Reflex, IXL, Prodigy. They all do practice, and they all give you a session percentage at the end. None of them did the thing I actually needed. Some of them I don't even know how they are allow to call themselves educational apps. Looking at you Prodigy. So I built it. The mechanic The engine is a speed adaptive Leitner plus SM-2 hybrid. Each fact lives in a box. Get the fact right in under three seconds, the fact promotes one box and the interval to the next time she sees it widens. Get it right in three to five seconds, the fact stays in the current box. Take longer than five, the fact demotes two boxes.…