Solve the hidden message where each letter of the alphabet has been substituted for another, for example, all e's become x's.

Each time you enter a coded letter (via virtual or real keyboard), all the others of the same letter will be filled in automatically. To change your guess, enter another letter in it's place.
Each incorrect entry (including clearing an entry) is recorded and your error count will be shown when you have successfully cracked the code.
Pressing the "Hint" icon will reveal the currently highlighted letter.