# What spaced repetition is

> The one idea behind Deckberry — and why it shapes every good card.

This is the only page that explains the theory. Read it once and you'll understand why
the rest of the guide keeps pushing you toward small, clear, one-idea cards.

## The idea

**Spaced repetition** means reviewing something right before you'd forget it. Each time
you successfully recall a fact, the memory lasts a little longer — so the next review
can wait a little longer too. Review too early and you waste effort; too late and it's
already gone. Spacing the reviews to match forgetting is the most efficient way known
to move things into long-term memory.

Deckberry does the spacing for you. After each card, the learner rates how well they
recalled it, and the schedule stretches or shrinks automatically — easy cards drift
weeks apart, shaky ones return tomorrow. Neither you nor the learner manages any of it.

## Why it shapes your cards

Here's the part that matters for creators: the schedule only works if each review is a
clean **pass or fail**. The app needs to know "did they recall this?" — one honest
yes or no. That single requirement is where every deck-craft rule comes from:

- If a card asks for **two facts**, there's no single yes/no — so
  [one card, one fact](https://www.deckberry.com/creators/guide/deck-craft/one-fact/).
- If the front just **displays** a heading, there's nothing to recall — so
  [ask, don't display](https://www.deckberry.com/creators/guide/deck-craft/ask-dont-display/).
- If the answer is a **paragraph**, the learner can't honestly grade it — so
  [answers you can self-grade](https://www.deckberry.com/creators/guide/deck-craft/self-gradable/).

Get the cards clean and the scheduling takes care of the rest. That's the whole deal —
and it's the last time we'll lecture the theory. From here on, the guide teaches by
example.

## Related

- [What Deckberry is for creators](https://www.deckberry.com/creators/guide/getting-started/what-deckberry-is/)
- [The 10-minute overview](https://www.deckberry.com/creators/guide/getting-started/overview/)
- [One card, one fact](https://www.deckberry.com/creators/guide/deck-craft/one-fact/)

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[Read this guide on Deckberry](https://www.deckberry.com/creators/guide/getting-started/spaced-repetition/)