Strengthen Skills Button Doesn't work
Over 2 days I've used Strengthen Skills feature over 6 times. And each time it hasn't strengthened anything. I've gotten every answer right, I've done timed practice, practice without a timer, even the Wifi glitch to see if it would make a difference. It didn't. Then I tried to strengthen skills (French Tree) through the individual skill Strengthen. And it still doesn't strengthen. Is this because of the new feature, or am I just doing something wrong?
I always re-gild mine the day they lose their gold color. Usually one skill-specific review will turn a skill gold again, but sometimes it takes two tries and occasionally on a large skill set (10 lessons or so) it will take three tries. So maybe you just need to focus on one skill for several reviews.
I think if your skill set has been "un-gold" a few days, and if you hover for hints a lot, and if you miss a lot of questions, all of those might mean you have to do more review. All this is hearsay from what I've read on the forums, where people talk about their own experiences with reviewing lessons. I've not seen anything official from Duo that talks about how their algorithm works.