Practice made from your own sentences
The first thing most language apps do is hand you a sentence someone else wrote. The exercise is generic because the app does not know what you get wrong; it only knows what most people get wrong. You drill the most common mistakes in the language, whether or not they are yours.
Sparkslingo goes the other way. When a review produces a correction, that correction can become an exercise, and the exercise is built from your sentence. The prompt you see is the sentence you wrote, with the mistake you actually made, and the reason attached is the reason the app gave you at the time.
There are a few kinds, because not every mistake is best fixed the same way. Some are recognition: see the mistake again and pick the right form, so you learn to spot it. Some are correction: fix the sentence with nothing to choose from. Some are recall: produce the right form cold. And some ask you to write a new sentence of your own, then watch for the same pattern the next time you write.
The point is not the drill. The point is that the thing you are drilling is yours, a sentence you wrote about your day rather than a sentence about a family that lives in a textbook. Practice you can recognise as your own is practice you will actually do, and the pattern behind it is the same one the profile has been counting.
One caution, in the app’s own spirit: the exercises are only as good as the corrections they come from. If a suggestion was wrong (a language has more than one defensible answer, and a review can pick the older one), then the exercise inherits that. Tell us when one looks off, and the correction can be fixed. The app keeps your original, so you can always tell.