1;;; blackbox.el --- blackbox game in Emacs Lisp
2
3;; Copyright (C) 1985-1987, 1992, 2001-2021 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 <https://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.
119To learn how to play blackbox, see the documentation for function `blackbox'.
120
121The 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.
131Optional prefix argument is the number of balls; the default is 4.
132
133What is blackbox?
134
135Blackbox is a game of hide and seek played on an 8 by 8 grid (the
136Blackbox).  Your opponent (Emacs, in this case) has hidden several
137balls (usually 4) within this box.  By shooting rays into the box and
138observing where they emerge it is possible to deduce the positions of
139the hidden balls.  The fewer rays you use to find the balls, the lower
140your score.
141
142Overview of play:
143
144\\<blackbox-mode-map>\
145To play blackbox, type \\[blackbox].  An optional prefix argument
146specifies the number of balls to be hidden in the box; the default is
147four.
148
149The cursor can be moved around the box with the standard cursor
150movement keys.
151
152To shoot a ray, move the cursor to the edge of the box and press SPC.
153The result will be determined and the playfield updated.
154
155You may place or remove balls in the box by moving the cursor into the
156box and pressing \\[bb-romp].
157
158When you think the configuration of balls you have placed is correct,
159press \\[bb-done].  You will be informed whether you are correct or
160not, and be given your score.  Your score is the number of letters and
161numbers around the outside of the box plus five for each incorrectly
162placed ball.  If you placed any balls incorrectly, they will be
163indicated with `x', and their actual positions indicated with `o'.
164
165Details:
166
167There 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
182The rules for how balls deflect rays are simple and are best shown by
183example.
184
185As a ray approaches a ball it is deflected ninety degrees.  Rays can
186be deflected multiple times.  In the diagrams below, the dashes
187represent empty box locations and the letter `O' represents a ball.
188The entrance and exit points of each ray are marked with numbers as
189described under \"Detour\" above.  Note that the entrance and exit
190points are always interchangeable.  `*' denotes the path taken by the
191ray.
192
193Note carefully the relative positions of the ball and the ninety
194degree deflection it causes.
195
196    1
197  - * - - - - - -         - - - - - - - -         - - - - - - - -
198  - * - - - - - -         - - - - - - - -         - - - - - - - -
1991 * * - - - - - -         - - - - - - - -         - O - - - - O -
200  - - O - - - - -         - - O - - - - -         - - * * * * - -
201  - - - - - - - -         - - - * * * * * 2     3 * * * - - * - -
202  - - - - - - - -         - - - * - - - -         - - - O - * - -
203  - - - - - - - -         - - - * - - - -         - - - - * * - -
204  - - - - - - - -         - - - * - - - -         - - - - * - O -
205                                2                         3
206
207As mentioned above, a reflection occurs when a ray emerges from the same point
208it was sent in.  This can happen in several ways:
209
210
211  - - - - - - - -         - - - - - - - -          - - - - - - - -
212  - - - - O - - -         - - O - O - - -          - - - - - - - -
213R * * * * - - - -         - - - * - - - -          O - - - - - - -
214  - - - - O - - -         - - - * - - - -        R - - - - - - - -
215  - - - - - - - -         - - - * - - - -          - - - - - - - -
216  - - - - - - - -         - - - * - - - -          - - - - - - - -
217  - - - - - - - -       R * * * * - - - -          - - - - - - - -
218  - - - - - - - -         - - - - O - - -          - - - - - - - -
219
220In the first example, the ray is deflected downwards by the upper
221ball, then left by the lower ball, and finally retraces its path to
222its point of origin.  The second example is similar.  The third
223example is a bit anomalous but can be rationalized by realizing the
224ray never gets a chance to get into the box.  Alternatively, the ray
225can be thought of as being deflected downwards and immediately
226emerging from the box.
227
228A hit occurs when a ray runs straight into a ball:
229
230  - - - - - - - -         - - - - - - - -          - - - - - - - -
231  - - - - - - - -         - - - - - - - -          - - - - O - - -
232  - - - - - - - -         - - - - O - - -        H * * * * - - - -
233  - - - - - - - -       H * * * * O - - -          - - - * - - - -
234  - - - - - - - -         - - - - O - - -          - - - O - - - -
235H * * * O - - - -         - - - - - - - -          - - - - - - - -
236  - - - - - - - -         - - - - - - - -          - - - - - - - -
237  - - - - - - - -         - - - - - - - -          - - - - - - - -
238
239Be sure to compare the second example of a hit with the first example of
240a 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
432