lisp/play/blackbox.el

   1 ;;; blackbox.el --- blackbox game in Emacs Lisp
   2
   3 ;; Copyright (C) 1985-1987, 1992, 2001-2016 Free Software Foundation,
   4 ;; Inc.
   5
   6 ;; Author: F. Thomas May <uw-nsr!uw-warp!tom@beaver.cs.washington.edu>
   7 ;; Adapted-By: ESR
   8 ;; Keywords: games
   9
  10 ;; This file is part of GNU Emacs.
  11
  12 ;; GNU Emacs is free software: you can redistribute it and/or modify
  13 ;; it under the terms of the GNU General Public License as published by
  14 ;; the Free Software Foundation, either version 3 of the License, or
  15 ;; (at your option) any later version.
  16
  17 ;; GNU Emacs is distributed in the hope that it will be useful,
  18 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  19 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20 ;; GNU General Public License for more details.
  21
  22 ;; You should have received a copy of the GNU General Public License
  23 ;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
  24
  25 ;;; Commentary:
  26
  27 ;; by F. Thomas May <uw-nsr!uw-warp!tom@beaver.cs.washington.edu>
  28 ;; doc comment by Root Boy Jim <rbj@dsys.icst.nbs.gov>, 27 Apr 89
  29 ;; interface improvements by ESR, Dec 5 1991.
  30
  31 ;; The object of the game is to find four hidden balls by shooting rays
  32 ;; into the black box.  There are four possibilities: 1) the ray will
  33 ;; pass thru the box undisturbed, 2) it will hit a ball and be absorbed,
  34 ;; 3) it will be deflected and exit the box, or 4) be deflected immediately,
  35 ;; not even being allowed entry into the box.
  36 ;;
  37 ;; The strange part is the method of deflection.  It seems that rays will
  38 ;; not pass next to a ball, and change direction at right angles to avoid it.
  39 ;;
  40 ;;                           R   3
  41 ;;               1 - - - - - - - - 1
  42 ;;                 - - - - - - - -
  43 ;;                 - O - - - - - - 3
  44 ;;               2 - - - - O - O -
  45 ;;               4 - - - - - - - -
  46 ;;               5 - - - - - - - - 5
  47 ;;                 - - - - - - - - R
  48 ;;               H - - - - - - - O
  49 ;;                 2   H 4       H
  50 ;;
  51 ;; Rays which enter and exit are numbered.  You can see that rays 1 & 5 pass
  52 ;; thru the box undisturbed.  Ray 2 is deflected by the northwesternmost
  53 ;; ball.  Likewise rays 3 and 4. Rays which hit balls and are absorbed are
  54 ;; marked with H.  The bottom of the left and the right of the bottom hit
  55 ;; the southeastern ball directly.  Rays may also hit balls after being
  56 ;; reflected.  Consider the H on the bottom next to the 4.  It bounces off
  57 ;; the NW-ern most ball and hits the central ball.  A ray shot from above
  58 ;; the right side 5 would hit the SE-ern most ball.  The R beneath the 5
  59 ;; is because the ball is returned instantly.  It is not allowed into
  60 ;; the box if it would reflect immediately.  The R on the top is a more
  61 ;; leisurely return.  Both central balls would tend to deflect it east
  62 ;; or west, but it cannot go either way, so it just retreats.
  63 ;;
  64 ;; At the end of the game, if you've placed guesses for as many balls as
  65 ;; there are in the box, the true board position will be revealed.  Each
  66 ;; `x' is an incorrect guess of yours; `o' is the true location of a ball.
  67
  68 ;;; Code:
  69
  70 (defvar bb-board nil
  71   "Blackbox board.")
  72
  73 (defvar bb-x -1
  74   "Current x-position.")
  75
  76 (defvar bb-y -1
  77   "Current y-position.")
  78
  79 (defvar bb-score 0
  80   "Current score.")
  81
  82 (defvar bb-detour-count 0
  83   "Number of detours.")
  84
  85 (defvar bb-balls-placed nil
  86   "List of already placed balls.")
  87
  88 ;; This is used below to remap existing bindings for cursor motion to
  89 ;; blackbox-specific bindings in blackbox-mode-map.  This is so that
  90 ;; users who prefer non-default key bindings for cursor motion don't
  91 ;; lose that when they play Blackbox.
  92 (defun blackbox-redefine-key (map oldfun newfun)
  93   "Redefine keys that run the function OLDFUN to run NEWFUN instead."
  94   (define-key map (vector 'remap oldfun) newfun))
  95
  96
  97 (defvar blackbox-mode-map
  98   (let ((map (make-keymap)))
  99     (suppress-keymap map t)
 100     (blackbox-redefine-key map 'backward-char 'bb-left)
 101     (blackbox-redefine-key map 'left-char 'bb-left)
 102     (blackbox-redefine-key map 'forward-char 'bb-right)
 103     (blackbox-redefine-key map 'right-char 'bb-right)
 104     (blackbox-redefine-key map 'previous-line 'bb-up)
 105     (blackbox-redefine-key map 'next-line 'bb-down)
 106     (blackbox-redefine-key map 'move-end-of-line 'bb-eol)
 107     (blackbox-redefine-key map 'move-beginning-of-line 'bb-bol)
 108     (define-key map " " 'bb-romp)
 109     (define-key map "q" 'bury-buffer)
 110     (define-key map [insert] 'bb-romp)
 111     (define-key map [return] 'bb-done)
 112     (blackbox-redefine-key map 'newline 'bb-done)
 113     map))
 114
 115 ;; Blackbox mode is suitable only for specially formatted data.
 116
 117 (define-derived-mode blackbox-mode special-mode "Blackbox"
 118   "Major mode for playing blackbox.
 119 To learn how to play blackbox, see the documentation for function `blackbox'.
 120
 121 The usual mnemonic keys move the cursor around the box.
 122 \\<blackbox-mode-map>\\[bb-bol] and \\[bb-eol] move to the beginning and end of line, respectively.
 123
 124 \\[bb-romp] -- send in a ray from point, or toggle a ball at point
 125 \\[bb-done] -- end game and get score"
 126   (setq truncate-lines t))
 127
 128 ;;;###autoload
 129 (defun blackbox (num)
 130   "Play blackbox.
 131 Optional prefix argument is the number of balls; the default is 4.
 132
 133 What is blackbox?
 134
 135 Blackbox is a game of hide and seek played on an 8 by 8 grid (the
 136 Blackbox).  Your opponent (Emacs, in this case) has hidden several
 137 balls (usually 4) within this box.  By shooting rays into the box and
 138 observing where they emerge it is possible to deduce the positions of
 139 the hidden balls.  The fewer rays you use to find the balls, the lower
 140 your score.
 141
 142 Overview of play:
 143
 144 \\<blackbox-mode-map>\
 145 To play blackbox, type \\[blackbox].  An optional prefix argument
 146 specifies the number of balls to be hidden in the box; the default is
 147 four.
 148
 149 The cursor can be moved around the box with the standard cursor
 150 movement keys.
 151
 152 To shoot a ray, move the cursor to the edge of the box and press SPC.
 153 The result will be determined and the playfield updated.
 154
 155 You may place or remove balls in the box by moving the cursor into the
 156 box and pressing \\[bb-romp].
 157
 158 When you think the configuration of balls you have placed is correct,
 159 press \\[bb-done].  You will be informed whether you are correct or
 160 not, and be given your score.  Your score is the number of letters and
 161 numbers around the outside of the box plus five for each incorrectly
 162 placed ball.  If you placed any balls incorrectly, they will be
 163 indicated with `x', and their actual positions indicated with `o'.
 164
 165 Details:
 166
 167 There are three possible outcomes for each ray you send into the box:
 168
 169         Detour: the ray is deflected and emerges somewhere other than
 170                 where you sent it in.  On the playfield, detours are
 171                 denoted by matching pairs of numbers -- one where the
 172                 ray went in, and the other where it came out.
 173
 174         Reflection: the ray is reflected and emerges in the same place
 175                 it was sent in.  On the playfield, reflections are
 176                 denoted by the letter `R'.
 177
 178         Hit:    the ray strikes a ball directly and is absorbed.  It does
 179                 not emerge from the box.  On the playfield, hits are
 180                 denoted by the letter `H'.
 181
 182 The rules for how balls deflect rays are simple and are best shown by
 183 example.
 184
 185 As a ray approaches a ball it is deflected ninety degrees.  Rays can
 186 be deflected multiple times.  In the diagrams below, the dashes
 187 represent empty box locations and the letter `O' represents a ball.
 188 The entrance and exit points of each ray are marked with numbers as
 189 described under \"Detour\" above.  Note that the entrance and exit
 190 points are always interchangeable.  `*' denotes the path taken by the
 191 ray.
 192
 193 Note carefully the relative positions of the ball and the ninety
 194 degree deflection it causes.
 195
 196     1
 197   - * - - - - - -         - - - - - - - -         - - - - - - - -
 198   - * - - - - - -         - - - - - - - -         - - - - - - - -
 199 1 * * - - - - - -         - - - - - - - -         - O - - - - O -
 200   - - O - - - - -         - - O - - - - -         - - * * * * - -
 201   - - - - - - - -         - - - * * * * * 2     3 * * * - - * - -
 202   - - - - - - - -         - - - * - - - -         - - - O - * - -
 203   - - - - - - - -         - - - * - - - -         - - - - * * - -
 204   - - - - - - - -         - - - * - - - -         - - - - * - O -
 205                                 2                         3
 206
 207 As mentioned above, a reflection occurs when a ray emerges from the same point
 208 it was sent in.  This can happen in several ways:
 209
 210
 211   - - - - - - - -         - - - - - - - -          - - - - - - - -
 212   - - - - O - - -         - - O - O - - -          - - - - - - - -
 213 R * * * * - - - -         - - - * - - - -          O - - - - - - -
 214   - - - - O - - -         - - - * - - - -        R - - - - - - - -
 215   - - - - - - - -         - - - * - - - -          - - - - - - - -
 216   - - - - - - - -         - - - * - - - -          - - - - - - - -
 217   - - - - - - - -       R * * * * - - - -          - - - - - - - -
 218   - - - - - - - -         - - - - O - - -          - - - - - - - -
 219
 220 In the first example, the ray is deflected downwards by the upper
 221 ball, then left by the lower ball, and finally retraces its path to
 222 its point of origin.  The second example is similar.  The third
 223 example is a bit anomalous but can be rationalized by realizing the
 224 ray never gets a chance to get into the box.  Alternatively, the ray
 225 can be thought of as being deflected downwards and immediately
 226 emerging from the box.
 227
 228 A hit occurs when a ray runs straight into a ball:
 229
 230   - - - - - - - -         - - - - - - - -          - - - - - - - -
 231   - - - - - - - -         - - - - - - - -          - - - - O - - -
 232   - - - - - - - -         - - - - O - - -        H * * * * - - - -
 233   - - - - - - - -       H * * * * O - - -          - - - * - - - -
 234   - - - - - - - -         - - - - O - - -          - - - O - - - -
 235 H * * * O - - - -         - - - - - - - -          - - - - - - - -
 236   - - - - - - - -         - - - - - - - -          - - - - - - - -
 237   - - - - - - - -         - - - - - - - -          - - - - - - - -
 238
 239 Be sure to compare the second example of a hit with the first example of
 240 a reflection."
 241   (interactive "P")
 242   (switch-to-buffer "*Blackbox*")
 243   (blackbox-mode)
 244   (setq buffer-read-only t)
 245   (buffer-disable-undo (current-buffer))
 246   (setq bb-board (bb-init-board (or num 4)))
 247   (setq bb-balls-placed nil)
 248   (setq bb-x -1)
 249   (setq bb-y -1)
 250   (setq bb-score 0)
 251   (setq bb-detour-count 0)
 252   (bb-insert-board)
 253   (bb-goto (cons bb-x bb-y)))
 254
 255 (defun bb-init-board (num-balls)
 256   (let (board pos)
 257     (while (>= (setq num-balls (1- num-balls)) 0)
 258       (while
 259           (progn
 260             (setq pos (cons (random 8) (random 8)))
 261             (member pos board)))
 262       (setq board (cons pos board)))
 263     board))
 264
 265 (defun bb-insert-board ()
 266   (let (i (buffer-read-only nil))
 267     (erase-buffer)
 268     (insert "                     \n")
 269     (setq i 8)
 270     (while (>= (setq i (1- i)) 0)
 271       (insert "   - - - - - - - -   \n"))
 272     (insert "                     \n")
 273     (insert (format "\nThere are %d balls in the box" (length bb-board)))
 274     ))
 275
 276 (defun bb-right (count)
 277   (interactive "p")
 278   (while (and (> count 0) (< bb-x 8))
 279     (forward-char 2)
 280     (setq bb-x (1+ bb-x))
 281     (setq count (1- count))))
 282
 283 (defun bb-left (count)
 284   (interactive "p")
 285   (while (and (> count 0) (> bb-x -1))
 286     (backward-char 2)
 287     (setq bb-x (1- bb-x))
 288     (setq count (1- count))))
 289
 290 (defun bb-up (count)
 291   (interactive "p")
 292   (while (and (> count 0) (> bb-y -1))
 293     (with-no-warnings (previous-line))
 294     (setq bb-y (1- bb-y))
 295     (setq count (1- count))))
 296
 297 (defun bb-down (count)
 298   (interactive "p")
 299   (while (and (> count 0) (< bb-y 8))
 300     (with-no-warnings (next-line))
 301     (setq bb-y (1+ bb-y))
 302     (setq count (1- count))))
 303
 304 (defun bb-eol ()
 305   (interactive)
 306   (setq bb-x 8)
 307   (bb-goto (cons bb-x bb-y)))
 308
 309 (defun bb-bol ()
 310   (interactive)
 311   (setq bb-x -1)
 312   (bb-goto (cons bb-x bb-y)))
 313
 314 (defun bb-romp ()
 315   (interactive)
 316   (cond
 317    ((and
 318      (or (= bb-x -1) (= bb-x 8))
 319      (or (= bb-y -1) (= bb-y 8))))
 320    ((bb-outside-box bb-x bb-y)
 321     (bb-trace-ray bb-x bb-y))
 322    (t
 323     (bb-place-ball bb-x bb-y))))
 324
 325 (defun bb-place-ball (x y)
 326   (let ((coord (cons x y)))
 327     (cond
 328      ((member coord bb-balls-placed)
 329       (setq bb-balls-placed (delete coord bb-balls-placed))
 330       (bb-update-board "-"))
 331      (t
 332       (setq bb-balls-placed (cons coord bb-balls-placed))
 333       (bb-update-board (propertize "O" 'help-echo "Placed ball"))))))
 334
 335 (defun bb-trace-ray (x y)
 336   (when (= (following-char) 32)
 337     (let ((result (bb-trace-ray-2
 338                    t
 339                    x
 340                    (cond
 341                     ((= x -1) 1)
 342                     ((= x 8) -1)
 343                     (t 0))
 344                    y
 345                    (cond
 346                     ((= y -1) 1)
 347                     ((= y 8) -1)
 348                     (t 0)))))
 349       (cond
 350        ((eq result 'hit)
 351         (bb-update-board (propertize "H" 'help-echo "Hit"))
 352         (setq bb-score (1+ bb-score)))
 353        ((equal result (cons x y))
 354         (bb-update-board (propertize "R" 'help-echo "Reflection"))
 355         (setq bb-score (1+ bb-score)))
 356        (t
 357         (setq bb-detour-count (1+ bb-detour-count))
 358         (bb-update-board (propertize (format "%d" bb-detour-count)
 359                                      'help-echo "Detour"))
 360         (save-excursion
 361           (bb-goto result)
 362           (bb-update-board (propertize (format "%d" bb-detour-count)
 363                                        'help-echo "Detour")))
 364         (setq bb-score (+ bb-score 2)))))))
 365
 366 (defun bb-trace-ray-2 (first x dx y dy)
 367   (cond
 368    ((and (not first)
 369          (bb-outside-box x y))
 370     (cons x y))
 371    ((member (cons (+ x dx) (+ y dy)) bb-board)
 372     'hit)
 373    ((member (cons (+ x dx dy) (+ y dy dx)) bb-board)
 374     (bb-trace-ray-2 nil x (- dy) y (- dx)))
 375    ((member (cons (+ x dx (- dy)) (+ y dy (- dx))) bb-board)
 376     (bb-trace-ray-2 nil x dy y dx))
 377    (t
 378     (bb-trace-ray-2 nil (+ x dx) dx (+ y dy) dy))))
 379
 380 (defun bb-done ()
 381   "Finish the game and report score."
 382   (interactive)
 383   (let (bogus-balls)
 384     (cond
 385      ((not (= (length bb-balls-placed) (length bb-board)))
 386       (message "There %s %d hidden ball%s; you have placed %d."
 387                (if (= (length bb-board) 1) "is" "are")
 388                (length bb-board)
 389                (if (= (length bb-board) 1) "" "s")
 390                (length bb-balls-placed)))
 391      (t
 392       (setq bogus-balls (bb-show-bogus-balls bb-balls-placed bb-board))
 393       (if (= bogus-balls 0)
 394           (message "Right!  Your score is %d." bb-score)
 395         (message "Oops!  You missed %d ball%s.  Your score is %d."
 396                  bogus-balls
 397                  (if (= bogus-balls 1) "" "s")
 398                  (+ bb-score (* 5 bogus-balls))))
 399       (bb-goto '(-1 . -1))))))
 400
 401 (defun bb-show-bogus-balls (balls-placed board)
 402   (bb-show-bogus-balls-2 balls-placed board "x")
 403   (bb-show-bogus-balls-2 board balls-placed "o"))
 404
 405 (defun bb-show-bogus-balls-2 (list-1 list-2 c)
 406   (cond
 407    ((null list-1)
 408     0)
 409    ((member (car list-1) list-2)
 410     (bb-show-bogus-balls-2 (cdr list-1) list-2 c))
 411    (t
 412     (bb-goto (car list-1))
 413     (bb-update-board c)
 414     (1+ (bb-show-bogus-balls-2 (cdr list-1) list-2 c)))))
 415
 416 (defun bb-outside-box (x y)
 417   (or (= x -1) (= x 8) (= y -1) (= y 8)))
 418
 419 (defun bb-goto (pos)
 420   (goto-char (+ (* (car pos) 2) (* (cdr pos) 22) 26)))
 421
 422 (defun bb-update-board (c)
 423   (let ((buffer-read-only nil))
 424     (backward-char (1- (length c)))
 425     (delete-char (length c))
 426     (insert c)
 427     (backward-char 1)))
 428
 429 (provide 'blackbox)
 430
 431 ;;; blackbox.el ends here