MiniZini: transcript

This is MiniZini: an Android app where a child earns screen time by doing maths.

A parent picks the apps to limit, sets a PIN and a reward level. When time runs out, the app says it's time for a little break.

So the child trains: twelve questions a round, two minutes for every first-try answer, and a perfect round earns forty minutes.

At bedtime the apps rest, earned time is saved for tomorrow, and parents can add family prizes for real goals.

Under that simple loop is a lot of engineering, all on the phone, with no AI at runtime.

It enforces time with public Android tools: an accessibility service spots the app in front, usage stats measure real use, and a warning appears at five minutes and at one.

A protection check grades every device, and it even catches the case where every switch looks on, but apps still slip through.

Time is a transactional ledger: credits commit only when a round finishes, so quitting early earns nothing, and receipts survive reboots and clock changes.

The maths comes from a generative library: prompt, answer, hint and explanation are built from the same numbers, so they never disagree. Almost twenty-nine thousand questions, grades one to four.

When a skill needs practice, a gap check walks down the skill graph to find the weak foundation, then repairs it, across more than a thousand skills.

Forty-six kinds of figures, from number lines to clocks and protractors, are drawn natively from data and checked against golden screenshots.

Theory is read aloud in Latvian: almost nineteen hundred clips, checked by transcribing them back, and downloaded per grade on demand.

Builds are shrunk and profiled, a device test walks every topic, about fifteen hundred tests run, and each Play release waits for the owner's approval.

MiniZini. Maths that earns the screen time.