Crack the Alternating Code

A code can look as if it is changing its mind. One jump is big. The next is small. But watch this... when two rules take turns, every letter lands exactly where it should. Can you spot which rule moves next?

Picture two rule cards above a row. The blue card says, move forward three letters. The amber card says, move forward one letter. Blue goes first, then amber, then blue again. The rules alternate, like left foot, right foot. Trace each move with a curved arrow. Start on a letter, use only the next card, and write the landing letter. Then swap cards. Do not apply both rules at once, and do not choose whichever jump seems convenient. The alphabet is a loop, not a wall. If a move passes Z, wrap round to A and keep counting. For example, moving forward three from X gives A: Y is one, Z is two, A is three.

Let's work through an example. A code begins W, Z, A, D, E, blank. Rule one is move forward three letters. Rule two is move forward one letter. The rules alternate, starting with rule one. Which letter fills the blank? Option A is F. Option B is G. Option C is H. Option D is I. Which option is correct? Mark the turns underneath: one, two, one, two, one. Now check the given code. W plus three lands on Z. Z plus one wraps round and lands on A. A plus three lands on D. D plus one lands on E. The pattern works. The next turn is rule one. Move forward three from E: F is one, G is two, H is three. The missing letter is H, so Option C is correct. Notice that we followed the rule card, not the nearest-looking answer.

When two code rules alternate, mark the turns, apply one rule at a time, and wrap from Z to A whenever needed. Keep the rhythm clear... rule one, rule two. You can crack the code!