+"""Enciphering and deciphering using the [Caesar cipher](https://en.wikipedia.org/wiki/Caesar_cipher).
+Also attempts to break messages that use a Caesar cipher.
+
+The Caesar cipher operates one letter at a time. It converts each letter to a
+number, then enciphers that number by adding the key. The result is taken mod
+26 and converted back into a letter.
+
+"""
+