Three Code-Breaking Puzzles to Warm Up Your Brain

Code-breaking puzzles reward a different skill than logic grids: instead of eliminating options from clues, you are looking for the single rule that turns one word into another. The three puzzles below are original, built around a letter-shift cipher, a backwards-alphabet riddle, and a missing-link word puzzle. Every answer was checked by testing every possible case.

The letter-shift idea behind puzzle 1 is one of the oldest tricks in cryptography. NRICH, the mathematics enrichment project run by the University of Cambridge, has a classic problem called "Some Secret Codes" that uses exactly this approach: move every letter a fixed number of places through the alphabet, and wrap around from the end back to the start when you run out of letters. NRICH illustrates this with a code wheel, where moving 3 places to the left turns "a b c" into "x y z" because the wheel wraps around. The puzzle below uses the same wrap-around idea, just with an unknown shift amount that you have to discover first.

A related NRICH article, "Cracking Codes," describes a slightly more advanced version of the same family of cipher: assigning numbers to letters and shifting them by a fixed amount, then grouping the result into blocks of letters so word lengths do not give the message away. That article also distinguishes a simple shift cipher from the historical Enigma machine, which transposed letters in a more complicated, changing way rather than a single fixed shift. The cipher in puzzle 1 below is the simple fixed-shift kind.

Puzzle 1: The secret code

In a secret code, the word EYEBROW is written as JDJGWTB. Using the same code, how is TOMATO written?

To find the rule, every one of the 26 possible letter shifts (the kind of substitution used in a classic Caesar cipher, where each letter moves a fixed number of places through the alphabet) was tested against the known pair.

Exactly one shift works: 5. Every letter in EYEBROW moves 5 places forward in the alphabet, wrapping around from Z back to A if needed, to produce JDJGWTB. Applying that same shift to TOMATO.

Applying the same shift gives YTRFYT, which is the answer.

Notice what the brute-force check actually bought you here. Without testing every shift, you might have guessed shift 5 correctly on the first try, or you might have spent a while trying shift 1, then shift 2, and so on by hand. Checking all 26 possibilities in a few lines of code removes the guessing entirely and also proves there is no second shift that happens to work by coincidence, since the code confirmed exactly one match.

Puzzle 2: The alphabet riddle

If you write the alphabet backwards, starting with Z, what is the 5th letter?

The backwards alphabet reads ZYXWVUTSRQPONMLKJIHGFEDCBA, and its 5th letter is V. This also matches a second way of checking the same answer: V is the 22nd letter of the normal forward alphabet, and counting 5 places into the backwards alphabet lands on the same letter as counting 22 places into the forward one, since 26 minus 5 plus 1 equals 22.

Both methods give V, confirming the answer two independent ways.

Puzzle 3: The missing link

Find one word that completes all three: ___WORK, ___SICK, ___MADE.

This type of puzzle is not solved by a formula the way a cipher is, so the check here is simply confirming the resulting compound words are genuine English words: HOMEWORK, HOMESICK, and HOMEMADE. All three are standard dictionary compounds built on the same root, HOME, which is the answer.

That gives HOMEWORK, HOMESICK and HOMEMADE, three recognizable words. This kind of puzzle has no single numeric rule to brute-force the way a cipher does, so the real test is simply whether every combination forms a word you would find in a dictionary, rather than two real words and one near-miss.

Answers

1. Secret code: YTRFYT. The cipher shifts every letter 5 places forward in the alphabet; this was the only shift, out of all 26 possible, that turns EYEBROW into JDJGWTB.
2. Alphabet riddle: V. The 5th letter of the reversed alphabet is the 22nd letter of the normal alphabet, and both calculations agree.
3. Missing link: HOME, forming HOMEWORK, HOMESICK, and HOMEMADE.

Key takeaways

• A letter-shift cipher can be solved without guessing by testing all 26 possible shifts against a known word pair and keeping only the one that fits.
• Reading the alphabet backwards is equivalent to counting from the opposite end of the forward alphabet, which gives you two independent ways to check the same answer.
• Missing-link word puzzles are checked differently from ciphers: the test is whether the resulting words are genuine, not a numeric rule.
• Testing a puzzle's rule against every possibility, rather than assuming the first idea that comes to mind, is what makes an answer trustworthy instead of a guess.