REM >penney
PRINT "*** Penney's Game ***"
REPEAT
  PRINT ' "Heads you pick first, tails I pick first."
  PRINT "And it is... ";
  WAIT 100
  ht% = RND(0 - TIME) AND 1
  IF ht% THEN
    PRINT "heads!"
    PROC_player_chooses(player$)
    computer$ = FN_optimal(player$)
    PRINT "I choose "; computer$; "."
  ELSE
    PRINT "tails!"
    computer$ = FN_random
    PRINT "I choose "; computer$; "."
    PROC_player_chooses(player$)
  ENDIF
  PRINT "Starting the game..." ' SPC 5;
  sequence$ = ""
  winner% = FALSE
  REPEAT
    WAIT 100
    roll% = RND AND 1
    IF roll% THEN
      sequence$ += "H"
      PRINT "H  ";
    ELSE
      PRINT "T  ";
      sequence$ += "T"
    ENDIF
    IF RIGHT$(sequence$, 3) = computer$ THEN
      PRINT ' "I won!"
      winner% = TRUE
    ELSE
      IF RIGHT$(sequence$, 3) = player$ THEN
        PRINT ' "Congratulations! You won."
        winner% = TRUE
      ENDIF
    ENDIF
  UNTIL winner%
  REPEAT
    valid% = FALSE
    INPUT "Another game? (Y/N) " another$
    IF INSTR("YN", another$) THEN valid% = TRUE
  UNTIL valid%
UNTIL another$ = "N"
PRINT "Thank you for playing!"
END
:
DEF PROC_player_chooses(RETURN sequence$)
LOCAL choice$, valid%, i%
REPEAT
  valid% = TRUE
  PRINT "Enter a sequence of three choices, each of them either H or T:"
  INPUT "> " sequence$
  IF LEN sequence$ <> 3 THEN valid% = FALSE
  IF valid% THEN
    FOR i% = 1 TO 3
      choice$ = MID$(sequence$, i%, 1)
      IF choice$ <> "H" AND choice$ <> "T" THEN valid% = FALSE
    NEXT
  ENDIF
UNTIL valid%
ENDPROC
:
DEF FN_random
LOCAL sequence$, choice%, i%
sequence$ = ""
FOR i% = 1 TO 3
  choice% = RND AND 1
  IF choice% THEN sequence$ += "H" ELSE sequence$ += "T"
NEXT
= sequence$
:
DEF FN_optimal(sequence$)
IF MID$(sequence$, 2, 1) = "H" THEN
  = "T" + LEFT$(sequence$, 2)
ELSE
  = "H" + LEFT$(sequence$, 2)
ENDIF