Why Spaced Repetition Is the Secret to Actually Remembering Code | codemirr

You learn a new concept. You understand it. You move on. Three weeks later, you can't remember how it worked.

Sound familiar? This is the **forgetting curve**, first described by Hermann Ebbinghaus in 1885. Without reinforcement, we forget roughly 70% of new material within 24 hours.

What Is Spaced Repetition?

Spaced repetition is a learning technique where you review material at increasing intervals. Instead of reviewing something every day, you review it at the optimal moment — just before you would have forgotten it.

The intervals grow over time:

Day 1: learn it

Day 2: first review

Day 6: second review

Day 21: third review

Day 60: fourth review

The SM-2 Algorithm

Most spaced repetition systems (Anki, SuperMemo, Execute Program) are based on the SM-2 algorithm. After each review, you rate how well you remembered:

0 = blackout (complete forgot)
1 = wrong but the answer was close
3 = correct but hard
4 = correct with hesitation
5 = perfect recall

If you score 3+, the next review interval increases. If you fail (0-2), it resets to 1 day.

Why It Works for Programming

Programming knowledge is especially suited for spaced repetition because:

**It's declarative** — syntax, APIs, and idioms can be distilled into Q&A form

**It compounds** — knowing `map` makes `flatMap` easier

**It's practical** — if you can recall a pattern cold, you can use it under pressure

codemirr's Review System

Our Pro review system builds a queue of flashcards from every lesson you complete. When you learn "Python list comprehensions vs JavaScript .map()", that becomes a reviewable card:

> **Q:** What's the Pythonic equivalent of `[1,2,3].map(n => n*2)`?

> **A:** `[n * 2 for n in [1,2,3]]`

The more you review, the longer the intervals. Eventually, you'll just *know* it.

Conclusion

Reading once is not learning. Spaced repetition turns passive exposure into durable knowledge. It's the difference between recognizing something and being able to use it.