I always liked tracking my income and expenses. There was an app called Spendee that I used a lot. I liked it. But it felt too complicated for me, so like every self-respecting developer, I switched to Excel. Excel was fine, but it wasn't enough. Doing anything useful required too much effort. So I thought, why not build it myself? Let me build something nice with Ruby on Rails. The project was up and running very quickly. Tests were written. Deployment was done. Everything worked well. I started using the app in real life. It was doing exactly what I needed, and I could track my finances cleanly. When I build a web project, I usually try to make it responsive and mobile-friendly. This is called mobile first . The reason I do this is purely personal — because I mostly use my phone. And for an app like this, where you're adding expenses on the go, responsive design makes more sense. Tailwind CSS helped a lot here, and I put together a responsive web app pretty quickly. But responsive alone wasn't enough.…