01The challenge
Every shop sells on credit, and the worker at the counter is the one who records it. Many workers cannot write a name or read a number, and the paper ledger gets lost and disputed.
Every credit app asks you to type the amount, which needs reading, arithmetic and a keyboard.
02What we built
We turned amount entry from a symbolic task into a visual one: a grid of banknote images the worker taps exactly as they would hand them over, voice confirmation, and large targets for hurried fingers.
We made the ledger honest: no transaction can be edited or deleted, enforced inside the database engine itself. A correction is a reversing entry with a written reason, so every past state can be rebuilt.
The app works fully offline, with backup and restore that merges copies without deleting anything.
03The outcome
Shop owners know their customers' balances precisely, workers record with confidence, and customers cannot deny what they took.