Made in Ghana for children from about two to eleven. They all work on a phone, and they all keep working when there is no internet.
Knowing numbers. For a child who is still getting to know what numbers are, before any adding begins.
Easy Sums. For a child who is ready to add, once numbers themselves are familiar.
Quick sums. For a child who adds below ten without thinking, and is ready for answers that pass ten.
Colours, then fractions. The basic colours from age two, and what "three out of six" means once those are known.
Times tables. Every product to 12 × 12, drilled until the answer arrives without counting.