# How we got here.

An occasional diary. Milestones, the problems that ate a week, and the measurements that proved me wrong. This is the story of this project. Stories for people who build, and for people who love to ride.

- [The number that was meant to tell you whether you are improving](https://www.sofapps.it/grade/diary/il-numero-che-doveva-dirti-se-stai-migliorando/) (25 September 2026): Building a single index that works for a beginner and for a professional is harder than it looks. Mine broke twice on a real user, and in the end the right answer was to remove it.
- [The trainer told me forty-two revolutions per minute](https://www.sofapps.it/grade/diary/il-rullo-mi-ha-detto-42-rpm/) (11 September 2026): Indoor cycling apps are full of fixed numbers chosen by someone who did not know who would be pedalling. On a beginner, a fixed number is not imprecise: it is wrong, and sometimes it hurts.
- [I built a fake trainer so I could build the real one](https://www.sofapps.it/grade/diary/ho-costruito-un-rullo-finto/) (28 August 2026): How you build an app that talks to hardware, when the hardware is not there.
- [A week reading papers before writing a single line](https://www.sofapps.it/grade/diary/una-settimana-di-paper/) (14 August 2026): The power needed to ride a bike has an equation, it dates from 1998, and you can reproduce it numerically to find out whether you understood it. On the difference between a law, a validated model and a convention.