The letters all correspond to a letter of the alphabet - each one offset by the same amount. The offset is randomly selected each game, as is the word to decode. If it's "z" and has been offset by 1, the coded letter is "a". "g" becomes
"h" etc.
Look for clues in the relationship between letters:
Consecutive letters can be a big help.
Double letters tend to be "ee" or "oo" but could also be "tt", "ll", "gg". If a double consonant appears
in places 3 and 4 then position 5 may well be a "y".
Have fun!