Mix up the lesson reviews
Often time the lesson review is very easy, with simple concepts such as "el cangrejo come una manzana".
I am currently at Possessives and Colors level. I wish it would mix up old and new concepts, so we don't, as they say in the exercise world, plateau
"el cangrejo come una manzana", one of my favorite Duolingo phrases so far. I believe there also was: "el cangrejo bebe la leche"
Duolingo is an interesting place to learn about nature. ;-)