The Japanese reading problem that made me build my own app

I’ve been learning Japanese for several years now. Not intensively, not full‑time, but consistently — textbooks, classes, homework, and a lot of reading that never quite felt as productive as it should.
In December I took the JLPT N4. While preparing for it, I spent a lot of time reading Japanese texts that were supposed to be appropriate for my level. And that’s where I kept running into the same problem over and over again.