1. Try the alphabet workbench
Each A–Z letter moves the same number of places. Encoding moves forwards; decoding with the same shift moves backwards. Z wraps to A. Lowercase stays lowercase; spaces, digits, punctuation and letters outside A–Z stay unchanged.
ABCDEFGHIJKLMNOPQRSTUVWXYZ
Transformed message
Shift 0 leaves the message unchanged. Try Z with shift 1, then decode the result with shift 1.
2. Solve three railway messages
Try a mission on paper before using the workbench. You can reveal the answer without completing it; this is practice, not a scored test.
Checking ignores letter case and extra spaces. Changing a mission clears your answer and hides the solution; the practice workbench stays yours.
3. Explain the rule
Think of the alphabet as a circle of 26 positions. For shift 3, Y has position 24: 24 + 3 = 27. Take away 26 to wrap to position 1, which is B. To decode B, 1 − 3 = −2; add 26 to reach 24, or Y.
- Why does encoding and then decoding with the same shift recover your message?
- Why does a shift of 26 land in the same place as a shift of 0?
- Try the word BANANA. What do you notice about repeated letters?
- There are only 26 possible shifts, including 0. How could someone try all of them?
A puzzle, not password protection: this simple alphabet substitution is easy to break. Do not use it to protect passwords, private information, or real messages. Modern encryption is not just an alphabet shift.
Fictional railway messages; no real travel advice. This page sends and saves none of your inputs. Reloading starts over. Do not enter personal information.