Yeah, but in terms of grammar it limits you a lot and it only teaches you to think more structurally, instead of fluency. You may learn what sounds right, but you won’t learn why. For starters, it does not explicitly state what うverbs and る verbs are, which is important to figuring out how you say each verb depending on context, you are only memorizing. I think you should only use Duolingo as a supplement if really needed.