lisp/play/blackbox.el

   1 ;;; blackbox.el --- blackbox game in Emacs Lisp
   2
   3 ;; Copyright (C) 1985, 1986, 1987, 1992, 2001, 2002 Free Software Foundation, Inc.
   4
   5 ;; Author: F. Thomas May <uw-nsr!uw-warp!tom@beaver.cs.washington.edu>
   6 ;; Adapted-By: ESR
   7 ;; Keywords: games
   8
   9 ;; This file is part of GNU Emacs.
  10
  11 ;; GNU Emacs is free software; you can redistribute it and/or modify
  12 ;; it under the terms of the GNU General Public License as published by
  13 ;; the Free Software Foundation; either version 2, or (at your option)
  14 ;; any later version.
  15
  16 ;; GNU Emacs is distributed in the hope that it will be useful,
  17 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19 ;; GNU General Public License for more details.
  20
  21 ;; You should have received a copy of the GNU General Public License
  22 ;; along with GNU Emacs; see the file COPYING.  If not, write to the
  23 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  24 ;; Boston, MA 02111-1307, USA.
  25
  26 ;;; Commentary:
  27
  28 ;; by F. Thomas May <uw-nsr!uw-warp!tom@beaver.cs.washington.edu>
  29 ;; doc comment by Root Boy Jim <rbj@dsys.icst.nbs.gov>, 27 Apr 89
  30 ;; interface improvements by ESR, Dec 5 1991.
  31
  32 ;; The object of the game is to find four hidden balls by shooting rays
  33 ;; into the black box.  There are four possibilities: 1) the ray will
  34 ;; pass thru the box undisturbed, 2) it will hit a ball and be absorbed,
  35 ;; 3) it will be deflected and exit the box, or 4) be deflected immediately,
  36 ;; not even being allowed entry into the box.
  37 ;;
  38 ;; The strange part is the method of deflection.  It seems that rays will
  39 ;; not pass next to a ball, and change direction at right angles to avoid it.
  40 ;;
  41 ;;                           R   3
  42 ;;               1 - - - - - - - - 1
  43 ;;                 - - - - - - - -
  44 ;;                 - O - - - - - - 3
  45 ;;               2 - - - - O - O -
  46 ;;               4 - - - - - - - -
  47 ;;               5 - - - - - - - - 5
  48 ;;                 - - - - - - - - R
  49 ;;               H - - - - - - - O
  50 ;;                 2   H 4       H
  51 ;;
  52 ;; Rays which enter and exit are numbered.  You can see that rays 1 & 5 pass
  53 ;; thru the box undisturbed. Ray 2 is deflected by the northwesternmost
  54 ;; ball.  Likewise rays 3 and 4. Rays which hit balls and are absorbed are
  55 ;; marked with H.  The bottom of the left and the right of the bottom hit
  56 ;; the southeastern ball directly.  Rays may also hit balls after being
  57 ;; reflected. Consider the H on the bottom next to the 4.  It bounces off
  58 ;; the NW-ern most ball and hits the central ball.  A ray shot from above
  59 ;; the right side 5 would hit the SE-ern most ball.  The R beneath the 5
  60 ;; is because the ball is returned instantly.  It is not allowed into
  61 ;; the box if it would reflect immediately.  The R on the top is a more
  62 ;; leisurely return.  Both central balls would tend to deflect it east
  63 ;; or west, but it cannot go either way, so it just retreats.
  64 ;;
  65 ;; At the end of the game, if you've placed guesses for as many balls as
  66 ;; there are in the box, the true board position will be revealed.  Each
  67 ;; `x' is an incorrect guess of yours; `o' is the true location of a ball.
  68
  69 ;;; Code:
  70
  71 (defvar blackbox-mode-map nil "")
  72
  73 (defvar bb-board nil
  74   "Blackbox board.")
  75
  76 (defvar bb-x -1
  77   "Current x-position.")
  78
  79 (defvar bb-y -1
  80   "Current y-position.")
  81
  82 (defvar bb-score 0
  83   "Current score.")
  84
  85 (defvar bb-detour-count 0
  86   "Number of detours.")
  87
  88 (defvar bb-balls-placed nil
  89   "List of already placed balls.")
  90
  91 (unless blackbox-mode-map
  92   (setq blackbox-mode-map (make-keymap))
  93   (suppress-keymap blackbox-mode-map t)
  94   (define-key blackbox-mode-map "\C-f" 'bb-right)
  95   (define-key blackbox-mode-map [right] 'bb-right)
  96   (define-key blackbox-mode-map "\C-b" 'bb-left)
  97   (define-key blackbox-mode-map [left] 'bb-left)
  98   (define-key blackbox-mode-map "\C-p" 'bb-up)
  99   (define-key blackbox-mode-map [up] 'bb-up)
 100   (define-key blackbox-mode-map "\C-n" 'bb-down)
 101   (define-key blackbox-mode-map [down] 'bb-down)
 102   (define-key blackbox-mode-map "\C-e" 'bb-eol)
 103   (define-key blackbox-mode-map "\C-a" 'bb-bol)
 104   (define-key blackbox-mode-map " " 'bb-romp)
 105   (define-key blackbox-mode-map [insert] 'bb-romp)
 106   (define-key blackbox-mode-map "\C-m" 'bb-done)
 107   (define-key blackbox-mode-map [kp-enter] 'bb-done))
 108
 109 ;; Blackbox mode is suitable only for specially formatted data.
 110 (put 'blackbox-mode 'mode-class 'special)
 111
 112 (defun blackbox-mode ()
 113   "Major mode for playing blackbox.
 114 To learn how to play blackbox, see the documentation for function `blackbox'.
 115
 116 The usual mnemonic keys move the cursor around the box.
 117 \\<blackbox-mode-map>\\[bb-bol] and \\[bb-eol] move to the beginning and end of line, respectively.
 118
 119 \\[bb-romp] -- send in a ray from point, or toggle a ball at point
 120 \\[bb-done] -- end game and get score
 121 "
 122   (interactive)
 123   (kill-all-local-variables)
 124   (use-local-map blackbox-mode-map)
 125   (setq truncate-lines t)
 126   (setq major-mode 'blackbox-mode)
 127   (setq mode-name "Blackbox"))
 128
 129 ;;;###autoload
 130 (defun blackbox (num)
 131   "Play blackbox.
 132 Optional prefix argument is the number of balls; the default is 4.
 133
 134 What is blackbox?
 135
 136 Blackbox is a game of hide and seek played on an 8 by 8 grid (the
 137 Blackbox).  Your opponent (Emacs, in this case) has hidden several
 138 balls (usually 4) within this box.  By shooting rays into the box and
 139 observing where they emerge it is possible to deduce the positions of
 140 the hidden balls.  The fewer rays you use to find the balls, the lower
 141 your score.
 142
 143 Overview of play:
 144
 145 \\<blackbox-mode-map>\
 146 To play blackbox, type \\[blackbox].  An optional prefix argument
 147 specifies the number of balls to be hidden in the box; the default is
 148 four.
 149
 150 The cursor can be moved around the box with the standard cursor
 151 movement keys.
 152
 153 To shoot a ray, move the cursor to the edge of the box and press SPC.
 154 The result will be determined and the playfield updated.
 155
 156 You may place or remove balls in the box by moving the cursor into the
 157 box and pressing \\[bb-romp].
 158
 159 When you think the configuration of balls you have placed is correct,
 160 press \\[bb-done].  You will be informed whether you are correct or
 161 not, and be given your score.  Your score is the number of letters and
 162 numbers around the outside of the box plus five for each incorrectly
 163 placed ball.  If you placed any balls incorrectly, they will be
 164 indicated with `x', and their actual positions indicated with `o'.
 165
 166 Details:
 167
 168 There are three possible outcomes for each ray you send into the box:
 169
 170         Detour: the ray is deflected and emerges somewhere other than
 171                 where you sent it in.  On the playfield, detours are
 172                 denoted by matching pairs of numbers -- one where the
 173                 ray went in, and the other where it came out.
 174
 175         Reflection: the ray is reflected and emerges in the same place
 176                 it was sent in.  On the playfield, reflections are
 177                 denoted by the letter `R'.
 178
 179         Hit:    the ray strikes a ball directly and is absorbed.  It does
 180                 not emerge from the box.  On the playfield, hits are
 181                 denoted by the letter `H'.
 182
 183 The rules for how balls deflect rays are simple and are best shown by
 184 example.
 185
 186 As a ray approaches a ball it is deflected ninety degrees.  Rays can
 187 be deflected multiple times.  In the diagrams below, the dashes
 188 represent empty box locations and the letter `O' represents a ball.
 189 The entrance and exit points of each ray are marked with numbers as
 190 described under \"Detour\" above.  Note that the entrance and exit
 191 points are always interchangeable.  `*' denotes the path taken by the
 192 ray.
 193
 194 Note carefully the relative positions of the ball and the ninety
 195 degree deflection it causes.
 196
 197     1
 198   - * - - - - - -         - - - - - - - -         - - - - - - - -
 199   - * - - - - - -         - - - - - - - -         - - - - - - - -
 200 1 * * - - - - - -         - - - - - - - -         - O - - - - O -
 201   - - O - - - - -         - - O - - - - -         - - * * * * - -
 202   - - - - - - - -         - - - * * * * * 2     3 * * * - - * - -
 203   - - - - - - - -         - - - * - - - -         - - - O - * - -
 204   - - - - - - - -         - - - * - - - -         - - - - * * - -
 205   - - - - - - - -         - - - * - - - -         - - - - * - O -
 206                                 2                         3
 207
 208 As mentioned above, a reflection occurs when a ray emerges from the same point
 209 it was sent in.  This can happen in several ways:
 210
 211
 212   - - - - - - - -         - - - - - - - -          - - - - - - - -
 213   - - - - O - - -         - - O - O - - -          - - - - - - - -
 214 R * * * * - - - -         - - - * - - - -          O - - - - - - -
 215   - - - - O - - -         - - - * - - - -        R - - - - - - - -
 216   - - - - - - - -         - - - * - - - -          - - - - - - - -
 217   - - - - - - - -         - - - * - - - -          - - - - - - - -
 218   - - - - - - - -       R * * * * - - - -          - - - - - - - -
 219   - - - - - - - -         - - - - O - - -          - - - - - - - -
 220
 221 In the first example, the ray is deflected downwards by the upper
 222 ball, then left by the lower ball, and finally retraces its path to
 223 its point of origin.  The second example is similar.  The third
 224 example is a bit anomalous but can be rationalized by realizing the
 225 ray never gets a chance to get into the box.  Alternatively, the ray
 226 can be thought of as being deflected downwards and immediately
 227 emerging from the box.
 228
 229 A hit occurs when a ray runs straight into a ball:
 230
 231   - - - - - - - -         - - - - - - - -          - - - - - - - -
 232   - - - - - - - -         - - - - - - - -          - - - - O - - -
 233   - - - - - - - -         - - - - O - - -        H * * * * - - - -
 234   - - - - - - - -       H * * * * O - - -          - - - * - - - -
 235   - - - - - - - -         - - - - O - - -          - - - O - - - -
 236 H * * * O - - - -         - - - - - - - -          - - - - - - - -
 237   - - - - - - - -         - - - - - - - -          - - - - - - - -
 238   - - - - - - - -         - - - - - - - -          - - - - - - - -
 239
 240 Be sure to compare the second example of a hit with the first example of
 241 a reflection."
 242   (interactive "P")
 243   (switch-to-buffer "*Blackbox*")
 244   (blackbox-mode)
 245   (setq buffer-read-only t)
 246   (buffer-disable-undo (current-buffer))
 247   (setq bb-board (bb-init-board (or num 4)))
 248   (setq bb-balls-placed nil)
 249   (setq bb-x -1)
 250   (setq bb-y -1)
 251   (setq bb-score 0)
 252   (setq bb-detour-count 0)
 253   (bb-insert-board)
 254   (bb-goto (cons bb-x bb-y)))
 255
 256 (defun bb-init-board (num-balls)
 257   (random t)
 258   (let (board pos)
 259     (while (>= (setq num-balls (1- num-balls)) 0)
 260       (while
 261           (progn
 262             (setq pos (cons (random 8) (random 8)))
 263             (member pos board)))
 264       (setq board (cons pos board)))
 265     board))
 266
 267 (defun bb-insert-board ()
 268   (let (i (buffer-read-only nil))
 269     (erase-buffer)
 270     (insert "                     \n")
 271     (setq i 8)
 272     (while (>= (setq i (1- i)) 0)
 273       (insert "   - - - - - - - -   \n"))
 274     (insert "                     \n")
 275     (insert (format "\nThere are %d balls in the box" (length bb-board)))
 276     ))
 277
 278 (defun bb-right (count)
 279   (interactive "p")
 280   (while (and (> count 0) (< bb-x 8))
 281     (forward-char 2)
 282     (setq bb-x (1+ bb-x))
 283     (setq count (1- count))))
 284
 285 (defun bb-left (count)
 286   (interactive "p")
 287   (while (and (> count 0) (> bb-x -1))
 288     (backward-char 2)
 289     (setq bb-x (1- bb-x))
 290     (setq count (1- count))))
 291
 292 (defun bb-up (count)
 293   (interactive "p")
 294   (while (and (> count 0) (> bb-y -1))
 295     (previous-line 1)
 296     (setq bb-y (1- bb-y))
 297     (setq count (1- count))))
 298
 299 (defun bb-down (count)
 300   (interactive "p")
 301   (while (and (> count 0) (< bb-y 8))
 302     (next-line 1)
 303     (setq bb-y (1+ bb-y))
 304     (setq count (1- count))))
 305
 306 (defun bb-eol ()
 307   (interactive)
 308   (setq bb-x 8)
 309   (bb-goto (cons bb-x bb-y)))
 310
 311 (defun bb-bol ()
 312   (interactive)
 313   (setq bb-x -1)
 314   (bb-goto (cons bb-x bb-y)))
 315
 316 (defun bb-romp ()
 317   (interactive)
 318   (cond
 319    ((and
 320      (or (= bb-x -1) (= bb-x 8))
 321      (or (= bb-y -1) (= bb-y 8))))
 322    ((bb-outside-box bb-x bb-y)
 323     (bb-trace-ray bb-x bb-y))
 324    (t
 325     (bb-place-ball bb-x bb-y))))
 326
 327 (defun bb-place-ball (x y)
 328   (let ((coord (cons x y)))
 329     (cond
 330      ((member coord bb-balls-placed)
 331       (setq bb-balls-placed (delete coord bb-balls-placed))
 332       (bb-update-board "-"))
 333      (t
 334       (setq bb-balls-placed (cons coord bb-balls-placed))
 335       (bb-update-board (propertize "O" 'help-echo "Placed ball"))))))
 336
 337 (defun bb-trace-ray (x y)
 338   (let ((result (bb-trace-ray-2
 339                  t
 340                  x
 341                  (cond
 342                   ((= x -1) 1)
 343                   ((= x 8) -1)
 344                   (t 0))
 345                  y
 346                  (cond
 347                   ((= y -1) 1)
 348                   ((= y 8) -1)
 349                   (t 0)))))
 350     (cond
 351      ((eq result 'hit)
 352       (bb-update-board (propertize "H" 'help-echo "Hit"))
 353       (setq bb-score (1+ bb-score)))
 354      ((equal result (cons x y))
 355       (bb-update-board (propertize "R" 'help-echo "Reflection"))
 356       (setq bb-score (1+ bb-score)))
 357      (t
 358       (setq bb-detour-count (1+ bb-detour-count))
 359       (bb-update-board (propertize (format "%d" bb-detour-count)
 360                                    'help-echo "Detour"))
 361       (save-excursion
 362         (bb-goto result)
 363         (bb-update-board (propertize (format "%d" bb-detour-count)
 364                                      'help-echo "Detour")))
 365       (setq bb-score (+ bb-score 2))))))
 366
 367 (defun bb-trace-ray-2 (first x dx y dy)
 368   (cond
 369    ((and (not first)
 370          (bb-outside-box x y))
 371     (cons x y))
 372    ((member (cons (+ x dx) (+ y dy)) bb-board)
 373     'hit)
 374    ((member (cons (+ x dx dy) (+ y dy dx)) bb-board)
 375     (bb-trace-ray-2 nil x (- dy) y (- dx)))
 376    ((member (cons (+ x dx (- dy)) (+ y dy (- dx))) bb-board)
 377     (bb-trace-ray-2 nil x dy y dx))
 378    (t
 379     (bb-trace-ray-2 nil (+ x dx) dx (+ y dy) dy))))
 380
 381 (defun bb-done ()
 382   "Finish the game and report score."
 383   (interactive)
 384   (let (bogus-balls)
 385     (cond
 386      ((not (= (length bb-balls-placed) (length bb-board)))
 387       (message "There %s %d hidden ball%s; you have placed %d."
 388                (if (= (length bb-board) 1) "is" "are")
 389                (length bb-board)
 390                (if (= (length bb-board) 1) "" "s")
 391                (length bb-balls-placed)))
 392      (t
 393       (setq bogus-balls (bb-show-bogus-balls bb-balls-placed bb-board))
 394       (if (= bogus-balls 0)
 395           (message "Right!  Your score is %d." bb-score)
 396         (message "Oops!  You missed %d ball%s.  Your score is %d."
 397                  bogus-balls
 398                  (if (= bogus-balls 1) "" "s")
 399                  (+ bb-score (* 5 bogus-balls))))
 400       (bb-goto '(-1 . -1))))))
 401
 402 (defun bb-show-bogus-balls (balls-placed board)
 403   (bb-show-bogus-balls-2 balls-placed board "x")
 404   (bb-show-bogus-balls-2 board balls-placed "o"))
 405
 406 (defun bb-show-bogus-balls-2 (list-1 list-2 c)
 407   (cond
 408    ((null list-1)
 409     0)
 410    ((member (car list-1) list-2)
 411     (bb-show-bogus-balls-2 (cdr list-1) list-2 c))
 412    (t
 413     (bb-goto (car list-1))
 414     (bb-update-board c)
 415     (1+ (bb-show-bogus-balls-2 (cdr list-1) list-2 c)))))
 416
 417 (defun bb-outside-box (x y)
 418   (or (= x -1) (= x 8) (= y -1) (= y 8)))
 419
 420 (defun bb-goto (pos)
 421   (goto-char (+ (* (car pos) 2) (* (cdr pos) 22) 26)))
 422
 423 (defun bb-update-board (c)
 424   (let ((buffer-read-only nil))
 425     (backward-char (1- (length c)))
 426     (delete-char (length c))
 427     (insert c)
 428     (backward-char 1)))
 429
 430 (provide 'blackbox)
 431
 432 ;;; blackbox.el ends here