Every card in Letter codes

Its position in the alphabet, counting A as 1

HintA is 1, B is 2 — carry on the same way.

WhyB is 2, C is 3, all the way to Z at 26. Numbers decode back into letters the same way — and the worked pair in the question shows you the system before you use it.

How far each letter has shifted along the alphabet

HintCompare the worked pair — count the jump, then use that same jump on the new word.

WhyThe move is fixed: if A becomes C, every letter goes two places forward. It can also run backwards, so check the direction from the example before you start.

Undo the shift, moving each letter back the same distance

HintWhatever the code did, do the reverse to return home.

WhyOne worked pair fixes the shift. To encode, apply it; to decode, reverse it — two directions of the same rule.

The alphabet wraps round and carries on from A

HintPicture the letters written in a circle rather than a line.

WhyAfter Z comes A again, and before A comes Z — so a shift of two forward turns Y into A. Watch out: letter SEQUENCES are different, and never wrap.

5

HintCount up from A on your fingers — it is not far.

WhyE is a handy anchor: from it you can reach D or F in one step instead of counting from A every time.

10

HintThe first letter to need double figures — a nice round number.

WhyJ at ten is the anchor for the front of the alphabet: A to J is exactly ten letters, so anything nearby is one or two hops away.

20

HintJ is ten — this one is twice as far along.

WhyE 5, J 10, T 20: with three anchors you rarely count more than a few letters in either direction.

26

HintThe very last letter — how many letters are there altogether?

WhyKnowing the alphabet ends at 26 lets you count from the back: the 25th letter is Y and the 24th is X.

M and N

HintThirteen letters on each side — the halfway pair.

WhyM is the 13th letter and N the 14th. Starting a count from the middle is often quicker than starting from A.

27

HintOne more than the number of letters in the alphabet.

WhyC is the 3rd letter, and 27 − 3 = 24, so C is the 24th from the end. Mirror-code questions lean on this constantly.