Speaking of language learning, I wish Duolingo could come with leveled readers. We build our intuition on languages only when we see words and phrases used in different context. Somehow it's hard to find good Spanish readers, compared with ample readers in English. I was trying to read the reading materials for the Mexico first graders (https://libros.conaliteg.gob.mx/primaria.html), oh boy, there are just too many new words for me even though I was at Duolingo Spanish unit 5. I used to use a reader called America Today. The book 2 talked about all the natural wonders of the US, and the book 3 talked about the America society: a day of supermarket manager, a day of a big city, and etc. The difficulty of the book was so well arranged that I had no problem progressing through it, and I had no problem with English grammar or day-to-day vocabularies after finishing the series.