Inside SM-18: the algorithm that decides when you review

Have you ever noticed that you can remember a word perfectly on Monday and completely blank on it by Friday? That's not you being bad at Chinese — that's just how human memory works. And it's exactly the problem our SM-18 algorithm was built to solve.

The forgetting curve (and why it's actually good news)

When you learn a new character, your memory of it starts fading almost immediately. Psychologists call this the forgetting curve, and at first glance it sounds depressing. But here's the good part: every time you recall a word just before you would have forgotten it, the memory comes back stronger and fades more slowly. Do this a few times and the word basically becomes permanent. So the secret isn't reviewing more — it's reviewing at the right moment. Too early and you're wasting time on things you already know. Too late and you're relearning from scratch. SM-18 lives in that sweet spot.

How the app gets to know your brain

Every time you tap "No", "Almost", "Yes" or "Easy" after flipping a card, you're not just answering a question — you're teaching the app something about your memory. Over time, SM-18 builds a little model of how you remember each specific word: how stable that memory is, how difficult the word seems to be for you, and how you've answered in the past. This is why two friends studying the exact same deck will end up with completely different review schedules. Maybe 蛋糕 (cake) sticks instantly for you but 尴尬 (awkward) refuses to stay put — the app notices, and adjusts. Your schedule is yours alone.

Why this beats cramming every time

We've all crammed for an exam and forgotten everything a week later. Cramming feels productive because it's intense, but the memories it creates are shallow. Spaced reviews are the opposite: a few minutes a day, almost effortless, and the words genuinely stay with you for months. In practice, most BoostChinese users finish their daily reviews in under ten minutes. That's the whole session. And it's enough to grow a vocabulary of thousands of characters over a year.

What this looks like day to day

You open the app, tap MyBrain, and the cards that are due today are simply there waiting for you — no planning, no deciding what to study. If a word is easy, hit "Easy" and it won't bother you again for a long time. If a word keeps tripping you up, it comes back sooner, along with its video and example sentences to give your memory more hooks to grab onto. That's really all there is to it. You show up, the algorithm remembers for you. 🧠