My implementation in Scheme of the game Word, that was published in BASIC Computer Games in 1978.

gamekata-word.csm

(use srfi-13 extras)

(define header #<<EOF
--------------------------------------------------------------------
                                 WORD
Adaption of original game in BASIC by Charles Reid of Lexington High
School, Massachusetts. Scheme version by Torbjørn Marø, 2014.
--------------------------------------------------------------------

I am thinking of a word -- you guess it. I will give you clues to
help you get it. Good luck!!
EOF
)

(define words 
  '("SMOKE" "CANDY" "DINKY" "WATER" "TRAIN" "NIGHT" "MIGHT" "FIRST"
    "CHAMP" "WOULD" "CLUMP" "DOPEY" "CRUSH" "EXTRA" "BASIC" "EIGHT"))

(define (random-elem lst)
  (list-ref lst (random (length lst))))

(define (random-sort l)
  (sort l
        (lambda (x y)
          (equal? 0 (random 2)))))

;;; The GAME-STATE data type

(define-record game-state word
                          current-guess
                          continue
                          matches
                          exact-matches
                          guess-count)

(define (init-game)
  (make-game-state 
    (random-elem words) ; word
    "     "             ; current-guess
    #t                  ; continue
    '()                 ; matches
    "-----"             ; exact-matches
    0))                 ; guess-count

(define (game-state-correct? state)
  (equal? (game-state-exact-matches state)
          (game-state-word state)))

;;; REPL logic

(define (game-read state)
  (display "\nGuess a five letter word? ")
  (let ((input (read-line)))
    (cond ((equal? input "?") 
           (game-state-current-guess-set! state "?")
           state)
          ((= 5 (string-length input))
           (game-state-current-guess-set! state 
             (string-upcase input))
           (game-state-guess-count-set! state 
             (+ (game-state-guess-count state) 1))
           state)
          (else
            (display "Bad input length! ") 
            (game-read state)))))

(define (find-matches state)
  (let loop ((i 0) (matches '()) (exact "-----"))
    (cond 
      ((< i 5)
       (let ((c (substring (game-state-word state) i (+ i 1)))
             (guess (game-state-current-guess state)))
         (when (string-contains guess c)
           (set! matches (cons c matches))
           (when (= i (string-index guess (string->char-set c)))
             (set! exact (string-replace exact c i (+ i 1))))))
       (loop (+ i 1) matches exact))
      (else
       (game-state-matches-set! state (random-sort matches))
       (game-state-exact-matches-set! state exact)))))
      
(define (game-eval state)
  (let ((guess (game-state-current-guess state)))
    (if (equal? guess "?")
      (game-state-continue-set! state #f)
      (find-matches state)))
  state)

(define (game-print state)
  (when (game-state-continue state)
    (printf 
      "There were ~A matches and the common letters were.. ~A~%"
      (length (game-state-matches state))
      (apply string-append (game-state-matches state)))
    (printf 
      "From the exact letter matches, you know........... ~A~%"
      (game-state-exact-matches state))
    (if (game-state-correct? state)
      (printf 
        "You have guessed the word. It took ~A guesses!~%"
        (game-state-guess-count state))
      (printf 
        "~%If you give up, type '?' for your next guess.~%")))
  state)

(define (start-game)
  (display "\nYou are starting a new game...\n")
  (let loop ((state (init-game)))
    (when (and (game-state-continue state)
               (not (game-state-correct? state)))
      (loop (game-print 
              (game-eval 
                (game-read state)))))))

;;; MAIN

(define (yes-or-no)
  (equal? "Y" (string-upcase (substring (read-line) 0 1))))

(display header)
(let loop ()
  (start-game)
  (display "Want to play again? ")
  (if (yes-or-no)
    (loop)
    (display "\nThanks for playing - bye bye!\n\n")))