1;;; blackbox.el --- blackbox game in Emacs Lisp
2
3;; Copyright (C) 1985, 1986, 1987, 1992, 2001, 2002, 2003, 2004,
4;;   2005, 2006, 2007 Free Software Foundation, 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 2, or (at your option)
15;; 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; see the file COPYING.  If not, write to the
24;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
25;; Boston, MA 02110-1301, USA.
26
27;;; Commentary:
28
29;; by F. Thomas May <uw-nsr!uw-warp!tom@beaver.cs.washington.edu>
30;; doc comment by Root Boy Jim <rbj@dsys.icst.nbs.gov>, 27 Apr 89
31;; interface improvements by ESR, Dec 5 1991.
32
33;; The object of the game is to find four hidden balls by shooting rays
34;; into the black box.  There are four possibilities: 1) the ray will
35;; pass thru the box undisturbed, 2) it will hit a ball and be absorbed,
36;; 3) it will be deflected and exit the box, or 4) be deflected immediately,
37;; not even being allowed entry into the box.
38;;
39;; The strange part is the method of deflection.  It seems that rays will
40;; not pass next to a ball, and change direction at right angles to avoid it.
41;;
42;; 		             R   3
43;; 		 1 - - - - - - - - 1
44;; 		   - - - - - - - -
45;; 		   - O - - - - - - 3
46;; 		 2 - - - - O - O -
47;; 		 4 - - - - - - - -
48;; 		 5 - - - - - - - - 5
49;; 		   - - - - - - - - R
50;; 		 H - - - - - - - O
51;; 		   2   H 4       H
52;;
53;; Rays which enter and exit are numbered.  You can see that rays 1 & 5 pass
54;; thru the box undisturbed.  Ray 2 is deflected by the northwesternmost
55;; ball.  Likewise rays 3 and 4. Rays which hit balls and are absorbed are
56;; marked with H.  The bottom of the left and the right of the bottom hit
57;; the southeastern ball directly.  Rays may also hit balls after being
58;; reflected.  Consider the H on the bottom next to the 4.  It bounces off
59;; the NW-ern most ball and hits the central ball.  A ray shot from above
60;; the right side 5 would hit the SE-ern most ball.  The R beneath the 5
61;; is because the ball is returned instantly.  It is not allowed into
62;; the box if it would reflect immediately.  The R on the top is a more
63;; leisurely return.  Both central balls would tend to deflect it east
64;; or west, but it cannot go either way, so it just retreats.
65;;
66;; At the end of the game, if you've placed guesses for as many balls as
67;; there are in the box, the true board position will be revealed.  Each
68;; `x' is an incorrect guess of yours; `o' is the true location of a ball.
69
70;;; Code:
71
72(defvar bb-board nil
73  "Blackbox board.")
74
75(defvar bb-x -1
76  "Current x-position.")
77
78(defvar bb-y -1
79  "Current y-position.")
80
81(defvar bb-score 0
82  "Current score.")
83
84(defvar bb-detour-count 0
85  "Number of detours.")
86
87(defvar bb-balls-placed nil
88  "List of already placed balls.")
89
90;; This is used below to remap existing bindings for cursor motion to
91;; blackbox-specific bindings in blackbox-mode-map.  This is so that
92;; users who prefer non-default key bindings for cursor motion don't
93;; lose that when they play Blackbox.
94(defun blackbox-redefine-key (map oldfun newfun)
95  "Redefine keys that run the function OLDFUN to run NEWFUN instead."
96  (define-key map (vector 'remap oldfun) newfun))
97
98
99(defvar blackbox-mode-map
100  (let ((map (make-keymap)))
101    (suppress-keymap map t)
102    (blackbox-redefine-key map 'backward-char 'bb-left)
103    (blackbox-redefine-key map 'forward-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 [insert] 'bb-romp)
110    (blackbox-redefine-key map 'newline 'bb-done)
111    map))
112
113;; Blackbox mode is suitable only for specially formatted data.
114(put 'blackbox-mode 'mode-class 'special)
115
116(defun blackbox-mode ()
117  "Major mode for playing blackbox.
118To learn how to play blackbox, see the documentation for function `blackbox'.
119
120The usual mnemonic keys move the cursor around the box.
121\\<blackbox-mode-map>\\[bb-bol] and \\[bb-eol] move to the beginning and end of line, respectively.
122
123\\[bb-romp] -- send in a ray from point, or toggle a ball at point
124\\[bb-done] -- end game and get score"
125  (interactive)
126  (kill-all-local-variables)
127  (use-local-map blackbox-mode-map)
128  (setq truncate-lines t)
129  (setq major-mode 'blackbox-mode)
130  (setq mode-name "Blackbox")
131  (run-mode-hooks 'blackbox-mode-hook))
132
133;;;###autoload
134(defun blackbox (num)
135  "Play blackbox.
136Optional prefix argument is the number of balls; the default is 4.
137
138What is blackbox?
139
140Blackbox is a game of hide and seek played on an 8 by 8 grid (the
141Blackbox).  Your opponent (Emacs, in this case) has hidden several
142balls (usually 4) within this box.  By shooting rays into the box and
143observing where they emerge it is possible to deduce the positions of
144the hidden balls.  The fewer rays you use to find the balls, the lower
145your score.
146
147Overview of play:
148
149\\<blackbox-mode-map>\
150To play blackbox, type \\[blackbox].  An optional prefix argument
151specifies the number of balls to be hidden in the box; the default is
152four.
153
154The cursor can be moved around the box with the standard cursor
155movement keys.
156
157To shoot a ray, move the cursor to the edge of the box and press SPC.
158The result will be determined and the playfield updated.
159
160You may place or remove balls in the box by moving the cursor into the
161box and pressing \\[bb-romp].
162
163When you think the configuration of balls you have placed is correct,
164press \\[bb-done].  You will be informed whether you are correct or
165not, and be given your score.  Your score is the number of letters and
166numbers around the outside of the box plus five for each incorrectly
167placed ball.  If you placed any balls incorrectly, they will be
168indicated with `x', and their actual positions indicated with `o'.
169
170Details:
171
172There are three possible outcomes for each ray you send into the box:
173
174	Detour: the ray is deflected and emerges somewhere other than
175		where you sent it in.  On the playfield, detours are
176		denoted by matching pairs of numbers -- one where the
177		ray went in, and the other where it came out.
178
179	Reflection: the ray is reflected and emerges in the same place
180		it was sent in.  On the playfield, reflections are
181		denoted by the letter `R'.
182
183	Hit:	the ray strikes a ball directly and is absorbed.  It does
184		not emerge from the box.  On the playfield, hits are
185		denoted by the letter `H'.
186
187The rules for how balls deflect rays are simple and are best shown by
188example.
189
190As a ray approaches a ball it is deflected ninety degrees.  Rays can
191be deflected multiple times.  In the diagrams below, the dashes
192represent empty box locations and the letter `O' represents a ball.
193The entrance and exit points of each ray are marked with numbers as
194described under \"Detour\" above.  Note that the entrance and exit
195points are always interchangeable.  `*' denotes the path taken by the
196ray.
197
198Note carefully the relative positions of the ball and the ninety
199degree deflection it causes.
200
201    1
202  - * - - - - - -         - - - - - - - -         - - - - - - - -
203  - * - - - - - -         - - - - - - - -         - - - - - - - -
2041 * * - - - - - -         - - - - - - - -         - O - - - - O -
205  - - O - - - - -         - - O - - - - -         - - * * * * - -
206  - - - - - - - -         - - - * * * * * 2     3 * * * - - * - -
207  - - - - - - - -         - - - * - - - -         - - - O - * - -
208  - - - - - - - -         - - - * - - - -         - - - - * * - -
209  - - - - - - - -         - - - * - - - -         - - - - * - O -
210                                2                         3
211
212As mentioned above, a reflection occurs when a ray emerges from the same point
213it was sent in.  This can happen in several ways:
214
215
216  - - - - - - - -         - - - - - - - -          - - - - - - - -
217  - - - - O - - -         - - O - O - - -          - - - - - - - -
218R * * * * - - - -         - - - * - - - -          O - - - - - - -
219  - - - - O - - -         - - - * - - - -        R - - - - - - - -
220  - - - - - - - -         - - - * - - - -          - - - - - - - -
221  - - - - - - - -         - - - * - - - -          - - - - - - - -
222  - - - - - - - -       R * * * * - - - -          - - - - - - - -
223  - - - - - - - -         - - - - O - - -          - - - - - - - -
224
225In the first example, the ray is deflected downwards by the upper
226ball, then left by the lower ball, and finally retraces its path to
227its point of origin.  The second example is similar.  The third
228example is a bit anomalous but can be rationalized by realizing the
229ray never gets a chance to get into the box.  Alternatively, the ray
230can be thought of as being deflected downwards and immediately
231emerging from the box.
232
233A hit occurs when a ray runs straight into a ball:
234
235  - - - - - - - -         - - - - - - - -          - - - - - - - -
236  - - - - - - - -         - - - - - - - -          - - - - O - - -
237  - - - - - - - -         - - - - O - - -        H * * * * - - - -
238  - - - - - - - -       H * * * * O - - -          - - - * - - - -
239  - - - - - - - -         - - - - O - - -          - - - O - - - -
240H * * * O - - - -         - - - - - - - -          - - - - - - - -
241  - - - - - - - -         - - - - - - - -          - - - - - - - -
242  - - - - - - - -         - - - - - - - -          - - - - - - - -
243
244Be sure to compare the second example of a hit with the first example of
245a reflection."
246  (interactive "P")
247  (switch-to-buffer "*Blackbox*")
248  (blackbox-mode)
249  (setq buffer-read-only t)
250  (buffer-disable-undo (current-buffer))
251  (setq bb-board (bb-init-board (or num 4)))
252  (setq bb-balls-placed nil)
253  (setq bb-x -1)
254  (setq bb-y -1)
255  (setq bb-score 0)
256  (setq bb-detour-count 0)
257  (bb-insert-board)
258  (bb-goto (cons bb-x bb-y)))
259
260(defun bb-init-board (num-balls)
261  (random t)
262  (let (board pos)
263    (while (>= (setq num-balls (1- num-balls)) 0)
264      (while
265	  (progn
266	    (setq pos (cons (random 8) (random 8)))
267	    (member pos board)))
268      (setq board (cons pos board)))
269    board))
270
271(defun bb-insert-board ()
272  (let (i (buffer-read-only nil))
273    (erase-buffer)
274    (insert "                     \n")
275    (setq i 8)
276    (while (>= (setq i (1- i)) 0)
277      (insert "   - - - - - - - -   \n"))
278    (insert "                     \n")
279    (insert (format "\nThere are %d balls in the box" (length bb-board)))
280    ))
281
282(defun bb-right (count)
283  (interactive "p")
284  (while (and (> count 0) (< bb-x 8))
285    (forward-char 2)
286    (setq bb-x (1+ bb-x))
287    (setq count (1- count))))
288
289(defun bb-left (count)
290  (interactive "p")
291  (while (and (> count 0) (> bb-x -1))
292    (backward-char 2)
293    (setq bb-x (1- bb-x))
294    (setq count (1- count))))
295
296(defun bb-up (count)
297  (interactive "p")
298  (while (and (> count 0) (> bb-y -1))
299    (previous-line 1)
300    (setq bb-y (1- bb-y))
301    (setq count (1- count))))
302
303(defun bb-down (count)
304  (interactive "p")
305  (while (and (> count 0) (< bb-y 8))
306    (next-line 1)
307    (setq bb-y (1+ bb-y))
308    (setq count (1- count))))
309
310(defun bb-eol ()
311  (interactive)
312  (setq bb-x 8)
313  (bb-goto (cons bb-x bb-y)))
314
315(defun bb-bol ()
316  (interactive)
317  (setq bb-x -1)
318  (bb-goto (cons bb-x bb-y)))
319
320(defun bb-romp ()
321  (interactive)
322  (cond
323   ((and
324     (or (= bb-x -1) (= bb-x 8))
325     (or (= bb-y -1) (= bb-y 8))))
326   ((bb-outside-box bb-x bb-y)
327    (bb-trace-ray bb-x bb-y))
328   (t
329    (bb-place-ball bb-x bb-y))))
330
331(defun bb-place-ball (x y)
332  (let ((coord (cons x y)))
333    (cond
334     ((member coord bb-balls-placed)
335      (setq bb-balls-placed (delete coord bb-balls-placed))
336      (bb-update-board "-"))
337     (t
338      (setq bb-balls-placed (cons coord bb-balls-placed))
339      (bb-update-board (propertize "O" 'help-echo "Placed ball"))))))
340
341(defun bb-trace-ray (x y)
342  (when (= (following-char) 32)
343    (let ((result (bb-trace-ray-2
344                   t
345                   x
346                   (cond
347                    ((= x -1) 1)
348                    ((= x 8) -1)
349                    (t 0))
350                   y
351                   (cond
352                    ((= y -1) 1)
353                    ((= y 8) -1)
354                    (t 0)))))
355      (cond
356       ((eq result 'hit)
357        (bb-update-board (propertize "H" 'help-echo "Hit"))
358        (setq bb-score (1+ bb-score)))
359       ((equal result (cons x y))
360        (bb-update-board (propertize "R" 'help-echo "Reflection"))
361        (setq bb-score (1+ bb-score)))
362       (t
363        (setq bb-detour-count (1+ bb-detour-count))
364        (bb-update-board (propertize (format "%d" bb-detour-count)
365                                     'help-echo "Detour"))
366        (save-excursion
367          (bb-goto result)
368          (bb-update-board (propertize (format "%d" bb-detour-count)
369                                       'help-echo "Detour")))
370        (setq bb-score (+ bb-score 2)))))))
371
372(defun bb-trace-ray-2 (first x dx y dy)
373  (cond
374   ((and (not first)
375	 (bb-outside-box x y))
376    (cons x y))
377   ((member (cons (+ x dx) (+ y dy)) bb-board)
378    'hit)
379   ((member (cons (+ x dx dy) (+ y dy dx)) bb-board)
380    (bb-trace-ray-2 nil x (- dy) y (- dx)))
381   ((member (cons (+ x dx (- dy)) (+ y dy (- dx))) bb-board)
382    (bb-trace-ray-2 nil x dy y dx))
383   (t
384    (bb-trace-ray-2 nil (+ x dx) dx (+ y dy) dy))))
385
386(defun bb-done ()
387  "Finish the game and report score."
388  (interactive)
389  (let (bogus-balls)
390    (cond
391     ((not (= (length bb-balls-placed) (length bb-board)))
392      (message "There %s %d hidden ball%s; you have placed %d."
393	       (if (= (length bb-board) 1) "is" "are")
394	       (length bb-board)
395	       (if (= (length bb-board) 1) "" "s")
396	       (length bb-balls-placed)))
397     (t
398      (setq bogus-balls (bb-show-bogus-balls bb-balls-placed bb-board))
399      (if (= bogus-balls 0)
400	  (message "Right!  Your score is %d." bb-score)
401	(message "Oops!  You missed %d ball%s.  Your score is %d."
402		 bogus-balls
403		 (if (= bogus-balls 1) "" "s")
404		 (+ bb-score (* 5 bogus-balls))))
405      (bb-goto '(-1 . -1))))))
406
407(defun bb-show-bogus-balls (balls-placed board)
408  (bb-show-bogus-balls-2 balls-placed board "x")
409  (bb-show-bogus-balls-2 board balls-placed "o"))
410
411(defun bb-show-bogus-balls-2 (list-1 list-2 c)
412  (cond
413   ((null list-1)
414    0)
415   ((member (car list-1) list-2)
416    (bb-show-bogus-balls-2 (cdr list-1) list-2 c))
417   (t
418    (bb-goto (car list-1))
419    (bb-update-board c)
420    (1+ (bb-show-bogus-balls-2 (cdr list-1) list-2 c)))))
421
422(defun bb-outside-box (x y)
423  (or (= x -1) (= x 8) (= y -1) (= y 8)))
424
425(defun bb-goto (pos)
426  (goto-char (+ (* (car pos) 2) (* (cdr pos) 22) 26)))
427
428(defun bb-update-board (c)
429  (let ((buffer-read-only nil))
430    (backward-char (1- (length c)))
431    (delete-char (length c))
432    (insert c)
433    (backward-char 1)))
434
435(provide 'blackbox)
436
437;; arch-tag: 6c474c62-5617-4b10-9b44-ac430168c0e2
438;;; blackbox.el ends here
439