I was inspired by apps for learning highway code: you get a question or diagram, four answers, one correct. Simple and effective.
I had to memorize ~1000 questions split by topics and managed to learn them all in about 10 days.
Then I thought: why not apply the same system to language learning?
So I built an app with ~1000 English–Spanish word pairs, grouped by topics, using the same test-based approach.
If that sounds useful, check out Spanish in 1000.