My dream language learning app didn’t exist, so I built it

In the ten years I’ve been learning Spanish, I’ve tried almost everything. I’ve had a Duolingo streak of more than 500 days, taken online lessons on Preply, studied at in-person Spanish schools in Guatemala, worked through books like Madrigal’s Magic Key to Spanish, and downloaded more apps than I’m proud of.

Each method has its merits. But a few months ago, I began to feel lost with Spanish. I’d just given up on another Duolingo streak, and I wanted to find a way to make learning a daily habit again — one that actually helped me remember and use what I’d learned. No shade to Duolingo, though I honestly can’t point to much it taught me that I’ve gone on to use in conversation.

So I started thinking about what had worked for me.

I realised that much of the Spanish I feel most confident using came from sentence structures I originally learned through flashcards. I could take those patterns into a conversation and adapt them to say what I meant.

It wasn’t a glamorous discovery. Flashcards have a long history of working, and apps like Anki have earned their followings through spaced repetition and simplicity. Still, it seemed clear that flashcards needed to be part of the next stage of my learning.

The problem with flashcards

When I tried to build a new deck, I remembered how much work goes into making one. You identify a word you don’t know, look up its meaning, come up with an example sentence, check that the sentence is right, and only then get around to studying it. I know I’m not the only person who’s spent more time making flashcards than reviewing them.

The bigger problem, though, was what happened after I’d learned a card.

A flashcard is static. That’s useful when you’re trying to get a sentence into your head, but once you know it, the card has nothing more to offer. It doesn’t get harder. It doesn’t ask you to do anything new with the word. It just comes back a few weeks later, exactly as it was.

I’d open my deck, see a sentence I could recite without thinking, mark it “easy,” and move on. The scheduling algorithm was doing its job. The problem was that the sentence had stopped teaching me anything.

That feeling stuck with me even more than the tedium of making the cards. A flashcard has a useful life. Once you’ve mastered it, it can become dead weight in your review queue, taking up a slot that could have gone to something you’re still learning.

What I actually wanted

I kept coming back to two things.

First, I wanted something that would write the sentences for me. I didn’t want a definition that I then had to turn into an example myself. I wanted a natural sentence built around the word I was trying to learn — something I could imagine a speaker actually saying.

Second, I wanted the sentence to change when I’d learned it. If I mastered a card, I didn’t want it to sit in the deck forever or simply disappear. I wanted a harder version to take its place: the same word, the same basic idea, but with more grammar and more meaning to work through.

I couldn’t find a tool that did both, so I built one. It’s called Frase Cards.

You add a word — a verb, a noun, a phrase, whatever you’re working on — and Frase Cards generates example sentences around it, starting at a level that suits you. When you master a sentence, a more demanding version replaces it. You keep working with the word, but the deck asks more of you as you improve.

How one word keeps growing

Say you add hablar. Your first sentence might be as simple as Hablo español. — “I speak Spanish.”

Once you’re comfortable with that, the sentence can grow into Hablo español con mis amigos porque quiero mejorar.— “I speak Spanish with my friends because I want to improve.” It’s still built around the same word and thought, but now you’re handling a reason clause as well.

That’s one direction of growth: a sentence becoming more complex as you master it.

The other direction is tense. Say you added hablar because you wanted to practise it in the present. Once you’ve mastered that tense, the next one unlocks automatically, with new sentences ready to study. You don’t have to go back and make another set of flashcards for the past tense, then another for the future. The deck grows with you.

So after Hablo español, you might eventually see a preterite sentence: Anoche hablé español con unos turistas en el bar. — “Last night I spoke Spanish with some tourists at the bar.” Keep going, and hablar opens up in the imperfect, the future, and eventually the subjunctive. Each tense gives you something new to work on when you’re ready for it.

Frase Cards tracks both directions on a Mastery Grid for each word, with tenses down one side and sentence complexity across the other. You can watch it fill in cell by cell. That gives me a clearer sense of progress than a count of how many times I’ve seen a card.

Making sure the sentences are right

Generating sentences was the easy part to imagine. The harder part was trusting them.

A sentence that’s subtly wrong — or grammatically correct but unlike anything someone would naturally say — can teach you the wrong thing. And when you’re learning, you may not yet know enough to catch it.

So every sentence is drafted and then put through a separate check for natural phrasing, grammar, and translation before it’s added to a deck. I won’t claim that nothing can ever slip through. I built that extra step because I knew I needed to be able to trust the sentences I was studying.

Where it’s at now

Frase Cards now does the two things I wanted from the start: it writes the sentences, and it grows them once I’ve earned the next step. FSRS handles the review scheduling underneath, while the Mastery Grid shows how I’m progressing with each word. Watching those cells fill in has turned out to be more satisfying than I expected.

It currently covers Spanish, French, Italian, and European Portuguese. It’s free to try for 14 days, with no card required, and then costs £2.99 a month.

I built Frase Cards because, after ten years of trying almost everything else, it was still the language learning tool I wished existed. If you have your own flashcard graveyard — cards you’ve outgrown but keep reviewing anyway — try it and see whether a deck that grows with you makes the difference.

I’d love your feedback!

Also on Duolingo: I spent 200 days learning chess on Duolingo, and the Elo it gave me was far higher than my real rating on Chess.com. Read my Duolingo Chess review.