When I first started living in Japan, I tried to solve the “get words I encounter in real life into my flashcards” problem with a hack. The Japanese dictionary app I was using had the ability to export a word list to CSV. The flashcard app I was using had an import functionality. Surely I could make this work somehow.
So, here was the setup: I’d build a list of words in the dictionary, and export them to a CSV file in my dropbox. My laptop, sitting open on a desk in my tiny Japanese apartment, would sync the new file down. A macOS folder action would be triggered by the new file, which would run a script that would convert the CSV file to the format expected by my flashcards app, and put it into a new folder in dropbox. I could then import that new file in my flashcard app, and study away. The effect actually worked pretty well — I could export the list from the dictionary, wait a minute or two, and then import the converted deck into my flashcards app.
I was sitting on the train one day, chatting with another foreigner friend and explaining this setup, when they mused that it would be great if there were a single app that would just do that for you. This was the lightbulb moment, where I realized that I could make that app. It would eventually become Nihongo.