Was du baust und was es kostet

You are going to build a spending tracker with a camera in it.

You open the app, type an amount, pick a category, and — if you want — photograph the receipt. Everything is stored on the phone. A history tab lists what you logged and lets you search it. An insights tab shows where the month went. In the evening the phone reminds you to log the day. No account, no server, no internet: it works on a plane and in a lift.

By the end of module 6 that app is installable by strangers from the Play Store, and you can push a fix to it in about a minute.

Why this app and not a to-do list

Every beginner course builds a to-do list. This one does not, and the reason is not taste.

Apple's App Store Review Guidelines have a section called Minimum Functionality, guideline 4.2: if your app is not particularly useful, unique or "app-like", it does not belong on the App Store. A tutorial to-do list is the most rejected shape of first app there is, and so is anything that reads as a repackaged website.

A spending tracker with a camera in it clears that line comfortably, in three ways at once:

• It uses real hardware — the camera, the file system, a local notification.
• It holds content the user made — their own entries, their own photographs.
• It has no login and no backend, so Apple's account-deletion requirement never applies to you and Google's Data safety form is one honest click saying "no data collected".

Each of those removes a wall you would otherwise hit in module 6 with a finished app and no way through. Expense trackers are a crowded category, and we come back to that honestly at the end: "another expense tracker" is a perfectly good first ship and a poor product, and knowing the difference is worth more than pretending otherwise.