The big idea
A code is a rule
Spies, ancient kings, and computer scientists all share one trick: writing messages that look like nonsense to outsiders but make perfect sense to the people who know the RULE.
A simple code is just a substitution rule. "Shift every letter forward by 1: A → B, B → C…" Now "CAT" becomes "DBU".
Cracking a code means finding the RULE. You need pattern recognition (which letters repeat?), classification (vowel or consonant?), elimination (which rule fits ALL the examples?), and the if-then logic from Tier 9 to test guesses. Tier 10 calls on every earlier skill.
- A code = a rule for swapping letters or symbols.
- Crack a code by spotting the rule, then applying it backwards.
- Earlier-tier skills all show up: patterns, classification, elimination, if-then.