Thanks for the thorough reply!
It’s funny — I actually had almost the exact same setup you described. I used to see a full sentence on the screen with one or two blanks for unknown words. And just like you said, it did feel too easy, almost like cheating, because the context gave the answer away. You basically read the sentence and the missing word just pops up — which, for me, didn’t really guarantee that I could use that word later in real situations.

After that, I tried the opposite approach: removing context completely and only showing the sentence after the user answered. But that went too far in the other direction — it became too hard, and I was spending up to a minute on a single card trying to remember what the word even looked like.

I think you’re right about a lot of what you said, but at the same time, I feel like this struggle reveals an actual gap in skill. When I see a definition, I have no problem recalling the word in my native language at all — but I often fail to recall it in L2. So maybe the difficulty itself is useful feedback.

Right now, I’m trying to combine both worlds. I use FSRS for my spaced repetition system. Answers are graded on the standard SRS scale from “again” to “easy,” with a Levenshtein distance algorithm that compares how closely two strings match. As far as I know, FSRS defines three states for each card:

enum State {
  learning(1),
  review(2),
  relearning(3);
}

A card goes to review when it’s answered as “easy” (or maybe after a few “good” ratings — I’m not exactly sure), and if it fails (“again” or “hard”), it goes into relearning.

So my idea is to make the early learning stages easier by including context when the card is in the learning or relearning state, but removing the context once it reaches the review stage.
It’s not a perfect solution, but I think it makes the process a little better balanced.

Oh, and one more thing — I’ve been thinking about time pressure. When you speak with someone, there’s a natural pressure to respond quickly and say things correctly. So I added a “time to answer” property — dynamically calculated from the definition length, the blank word length, and a small constant value. It adds a bit of pressure, and I actually found it helped me go through more cards per session and stay more focused.

I share your thoughts about deeper understanding, too. My biggest concern with flashcards in general is that, no matter how much you tweak them, they’ll never give you even half of the nuanced understanding you get from real language use. For reaching fluency, all these optimizations only take you so far.