Decode the letter rule

An input code changes into an output code. At level 1, the same shift moves every letter forward or backward through A–Z. A shift is one, two, three or four places.

Compare M with N: that is one place forward. I becomes J, N becomes O and T becomes U. The same change fits all four positions.

These are letter codes; their outputs need not be words. Use the rule stated for the level, rather than searching for a word meaning.

The three examples all use the same rule. MINT becomes NJOU and PARK becomes QBSL. In ZANY, Z wraps to A, A becomes B, N becomes O and Y becomes Z: the output is ABOZ.

Wrapping works in both directions: one place forward from Z is A; one place backward from A is Z. Continue counting instead of stopping at the end of the alphabet.

Level 2 alternates two different shifts from the first letter. Level 3 reverses the letter order, then applies one shift. Every shift is still one to four places forward or backward. Only that level’s rule family is allowed.

Use the rule from the three examples: move every letter one place forward. What does FROG become?

Work through F, R, O and G in order. Check each position before choosing; a familiar-looking ending is not enough.

This checkpoint has two choices. In the practice, each of six questions gives three examples and four answer choices. You can take your time.