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Secret code

Encode a message by shifting every letter — the Caesar cipher.

Builder· ages 10–1225 minforord / chrstring methodsmodulo

cipher.py

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First load pulls ~10 MB of Python. Only happens once — the browser caches it after.

What should the output look like?

You should see the original message and its encoded version printed.

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How this works

The Caesar cipher shifts every letter along the alphabet by a fixed number. Named after Julius Caesar, who used it 2000 years ago. ord() turns a letter into a number, chr() turns it back.

Your turn — try these

1Write the DECODE version (negative shift) to reverse it.
2Try shift=13 — that's the famous ROT13 cipher used all over the internet.
3Preserve capital letters exactly — 'Hello' should encode to 'Khoor'.