One of the apps I work on, EasyFichi, exists because of a law. In Spain every company has to record when employees start and finish their work. That is Royal Decree-Law 8/2019, if you enjoy reading legal text, which I now do far more than I ever planned to. Most small businesses handle it with a paper sheet or an Excel file that nobody really trusts.
So the product is easy to describe and annoying to build. Let people clock in and out, and make the records hold up if an inspector ever asks to see them.
Legal text is a spec written by someone who hates specs
A law does not read like a task ticket. It tells you the outcome it wants and leaves the how to you, which sounds freeing until you realize you are now responsible for every gap it left behind. Can an employee edit a past entry? For how long? Who approves the change? What even counts as a valid record? The decree has strong opinions on some of this and total silence on the rest.
Turning that into Flutter screens and Firestore documents meant making a hundred small decisions and being ready to defend each one. Not "this looks nice" but "this is correct, and here is why."
Boring is the feature
When the domain is dull there is a temptation to make the app exciting anyway. Resist it. A time-tracking app has one job: be correct and be trusted. A manager should open it, see the truth, and close it again. The best compliment we get is that people forget it is there.
I have shipped flashier things. This one taught me the most, because "correct" is a much harder target to hit than "looks good."