Read what you were not meant to read.
Substitution hides the letters but keeps the habits of the language. Transposition keeps the letters but hides their order. Crack one of each.
Pick a mission and start.
Each one is solved the moment the message reads as English.
How this works: the ciphers are the classical ones from the course. The Caesar shift moves every letter along the alphabet. The substitution cipher uses one fixed scrambled alphabet. The transposition writes the message in rows and reads it out by columns, padding with X. Every cipher was checked against an independent Python version. The messages are short, so it is easier than a real attack on a long text.