13 /* Direction bitfields */
20 /* Rotations: Anticlockwise, Clockwise, Flip, general rotate */
21 #define A(x) ( (((x) & 0x07) << 1) | (((x) & 0x08) >> 3) )
22 #define C(x) ( (((x) & 0x0E) >> 1) | (((x) & 0x01) << 3) )
23 #define F(x) ( (((x) & 0x0C) >> 2) | (((x) & 0x03) << 2) )
24 #define ROT(x, n) ( ((n)&3) == 0 ? (x) : \
25 ((n)&3) == 1 ? A(x) : \
26 ((n)&3) == 2 ? F(x) : C(x) )
28 /* X and Y displacements */
29 #define X(x) ( (x) == R ? +1 : (x) == L ? -1 : 0 )
30 #define Y(x) ( (x) == D ? +1 : (x) == U ? -1 : 0 )
33 #define COUNT(x) ( (((x) & 0x08) >> 3) + (((x) & 0x04) >> 2) + \
34 (((x) & 0x02) >> 1) + ((x) & 0x01) )
38 #define WINDOW_OFFSET 16
44 float barrier_probability;
48 int width, height, wrapping, completed;
50 unsigned char *barriers;
53 #define OFFSET(x2,y2,x1,y1,dir,state) \
54 ( (x2) = ((x1) + (state)->width + X((dir))) % (state)->width, \
55 (y2) = ((y1) + (state)->height + Y((dir))) % (state)->height)
57 #define index(state, a, x, y) ( a[(y) * (state)->width + (x)] )
58 #define tile(state, x, y) index(state, (state)->tiles, x, y)
59 #define barrier(state, x, y) index(state, (state)->barriers, x, y)
65 static int xyd_cmp(void *av, void *bv) {
66 struct xyd *a = (struct xyd *)av;
67 struct xyd *b = (struct xyd *)bv;
76 if (a->direction < b->direction)
78 if (a->direction > b->direction)
83 static struct xyd *new_xyd(int x, int y, int direction)
85 struct xyd *xyd = snew(struct xyd);
88 xyd->direction = direction;
92 /* ----------------------------------------------------------------------
93 * Randomly select a new game seed.
96 char *new_game_seed(game_params *params)
99 * The full description of a Net game is far too large to
100 * encode directly in the seed, so by default we'll have to go
101 * for the simple approach of providing a random-number seed.
103 * (This does not restrict me from _later on_ inventing a seed
104 * string syntax which can never be generated by this code -
105 * for example, strings beginning with a letter - allowing me
106 * to type in a precise game, and have new_game detect it and
107 * understand it and do something completely different.)
110 sprintf(buf, "%d", rand());
114 /* ----------------------------------------------------------------------
115 * Construct an initial game state, given a seed and parameters.
118 game_state *new_game(game_params *params, char *seed)
122 tree234 *possibilities, *barriers;
123 int w, h, x, y, nbarriers;
125 assert(params->width > 2);
126 assert(params->height > 2);
129 * Create a blank game state.
131 state = snew(game_state);
132 w = state->width = params->width;
133 h = state->height = params->height;
134 state->wrapping = params->wrapping;
135 state->completed = FALSE;
136 state->tiles = snewn(state->width * state->height, unsigned char);
137 memset(state->tiles, 0, state->width * state->height);
138 state->barriers = snewn(state->width * state->height, unsigned char);
139 memset(state->barriers, 0, state->width * state->height);
142 * Set up border barriers if this is a non-wrapping game.
144 if (!state->wrapping) {
145 for (x = 0; x < state->width; x++) {
146 barrier(state, x, 0) |= U;
147 barrier(state, x, state->height-1) |= D;
149 for (y = 0; y < state->height; y++) {
150 barrier(state, y, 0) |= L;
151 barrier(state, y, state->width-1) |= R;
156 * Seed the internal random number generator.
158 rs = random_init(seed, strlen(seed));
161 * Construct the unshuffled grid.
163 * To do this, we simply start at the centre point, repeatedly
164 * choose a random possibility out of the available ways to
165 * extend a used square into an unused one, and do it. After
166 * extending the third line out of a square, we remove the
167 * fourth from the possibilities list to avoid any full-cross
168 * squares (which would make the game too easy because they
169 * only have one orientation).
171 * The slightly worrying thing is the avoidance of full-cross
172 * squares. Can this cause our unsophisticated construction
173 * algorithm to paint itself into a corner, by getting into a
174 * situation where there are some unreached squares and the
175 * only way to reach any of them is to extend a T-piece into a
178 * Answer: no it can't, and here's a proof.
180 * Any contiguous group of such unreachable squares must be
181 * surrounded on _all_ sides by T-pieces pointing away from the
182 * group. (If not, then there is a square which can be extended
183 * into one of the `unreachable' ones, and so it wasn't
184 * unreachable after all.) In particular, this implies that
185 * each contiguous group of unreachable squares must be
186 * rectangular in shape (any deviation from that yields a
187 * non-T-piece next to an `unreachable' square).
189 * So we have a rectangle of unreachable squares, with T-pieces
190 * forming a solid border around the rectangle. The corners of
191 * that border must be connected (since every tile connects all
192 * the lines arriving in it), and therefore the border must
193 * form a closed loop around the rectangle.
195 * But this can't have happened in the first place, since we
196 * _know_ we've avoided creating closed loops! Hence, no such
197 * situation can ever arise, and the naive grid construction
198 * algorithm will guaranteeably result in a complete grid
199 * containing no unreached squares, no full crosses _and_ no
202 possibilities = newtree234(xyd_cmp);
203 add234(possibilities, new_xyd(w/2, h/2, R));
204 add234(possibilities, new_xyd(w/2, h/2, U));
205 add234(possibilities, new_xyd(w/2, h/2, L));
206 add234(possibilities, new_xyd(w/2, h/2, D));
208 while (count234(possibilities) > 0) {
211 int x1, y1, d1, x2, y2, d2, d;
214 * Extract a randomly chosen possibility from the list.
216 i = random_upto(rs, count234(possibilities));
217 xyd = delpos234(possibilities, i);
223 OFFSET(x2, y2, x1, y1, d1, state);
226 printf("picked (%d,%d,%c) <-> (%d,%d,%c)\n",
227 x1, y1, "0RU3L567D9abcdef"[d1], x2, y2, "0RU3L567D9abcdef"[d2]);
231 * Make the connection. (We should be moving to an as yet
234 tile(state, x1, y1) |= d1;
235 assert(tile(state, x2, y2) == 0);
236 tile(state, x2, y2) |= d2;
239 * If we have created a T-piece, remove its last
242 if (COUNT(tile(state, x1, y1)) == 3) {
243 struct xyd xyd1, *xydp;
247 xyd1.direction = 0x0F ^ tile(state, x1, y1);
249 xydp = find234(possibilities, &xyd1, NULL);
253 printf("T-piece; removing (%d,%d,%c)\n",
254 xydp->x, xydp->y, "0RU3L567D9abcdef"[xydp->direction]);
256 del234(possibilities, xydp);
262 * Remove all other possibilities that were pointing at the
263 * tile we've just moved into.
265 for (d = 1; d < 0x10; d <<= 1) {
267 struct xyd xyd1, *xydp;
269 OFFSET(x3, y3, x2, y2, d, state);
276 xydp = find234(possibilities, &xyd1, NULL);
280 printf("Loop avoidance; removing (%d,%d,%c)\n",
281 xydp->x, xydp->y, "0RU3L567D9abcdef"[xydp->direction]);
283 del234(possibilities, xydp);
289 * Add new possibilities to the list for moving _out_ of
290 * the tile we have just moved into.
292 for (d = 1; d < 0x10; d <<= 1) {
296 continue; /* we've got this one already */
298 if (!state->wrapping) {
299 if (d == U && y2 == 0)
301 if (d == D && y2 == state->height-1)
303 if (d == L && x2 == 0)
305 if (d == R && x2 == state->width-1)
309 OFFSET(x3, y3, x2, y2, d, state);
311 if (tile(state, x3, y3))
312 continue; /* this would create a loop */
315 printf("New frontier; adding (%d,%d,%c)\n",
316 x2, y2, "0RU3L567D9abcdef"[d]);
318 add234(possibilities, new_xyd(x2, y2, d));
321 /* Having done that, we should have no possibilities remaining. */
322 assert(count234(possibilities) == 0);
323 freetree234(possibilities);
326 * Now compute a list of the possible barrier locations.
328 barriers = newtree234(xyd_cmp);
329 for (y = 0; y < state->height - (!state->wrapping); y++) {
330 for (x = 0; x < state->width - (!state->wrapping); x++) {
332 if (!(tile(state, x, y) & R))
333 add234(barriers, new_xyd(x, y, R));
334 if (!(tile(state, x, y) & D))
335 add234(barriers, new_xyd(x, y, D));
340 * Now shuffle the grid.
342 for (y = 0; y < state->height - (!state->wrapping); y++) {
343 for (x = 0; x < state->width - (!state->wrapping); x++) {
344 int orig = tile(state, x, y);
345 int rot = random_upto(rs, 4);
346 tile(state, x, y) = ROT(orig, rot);
351 * And now choose barrier locations. (We carefully do this
352 * _after_ shuffling, so that changing the barrier rate in the
353 * params while keeping the game seed the same will give the
354 * same shuffled grid and _only_ change the barrier locations.
355 * Also the way we choose barrier locations, by repeatedly
356 * choosing one possibility from the list until we have enough,
357 * is designed to ensure that raising the barrier rate while
358 * keeping the seed the same will provide a superset of the
359 * previous barrier set - i.e. if you ask for 10 barriers, and
360 * then decide that's still too hard and ask for 20, you'll get
361 * the original 10 plus 10 more, rather than getting 20 new
362 * ones and the chance of remembering your first 10.)
364 nbarriers = params->barrier_probability * count234(barriers);
365 assert(nbarriers >= 0 && nbarriers <= count234(barriers));
367 while (nbarriers > 0) {
370 int x1, y1, d1, x2, y2, d2;
373 * Extract a randomly chosen barrier from the list.
375 i = random_upto(rs, count234(barriers));
376 xyd = delpos234(barriers, i);
385 OFFSET(x2, y2, x1, y1, d1, state);
388 barrier(state, x1, y1) |= d1;
389 barrier(state, x2, y2) |= d2;
395 * Clean up the rest of the barrier list.
400 while ( (xyd = delpos234(barriers, 0)) != NULL)
403 freetree234(barriers);
411 game_state *dup_game(game_state *state)
415 ret = snew(game_state);
416 ret->width = state->width;
417 ret->height = state->height;
418 ret->wrapping = state->wrapping;
419 ret->completed = state->completed;
420 ret->tiles = snewn(state->width * state->height, unsigned char);
421 memcpy(ret->tiles, state->tiles, state->width * state->height);
422 ret->barriers = snewn(state->width * state->height, unsigned char);
423 memcpy(ret->barriers, state->barriers, state->width * state->height);
428 void free_game(game_state *state)
431 sfree(state->barriers);
435 /* ----------------------------------------------------------------------
440 * Compute which squares are reachable from the centre square, as a
441 * quick visual aid to determining how close the game is to
442 * completion. This is also a simple way to tell if the game _is_
443 * completed - just call this function and see whether every square
446 static unsigned char *compute_active(game_state *state)
448 unsigned char *active;
452 active = snewn(state->width * state->height, unsigned char);
453 memset(active, 0, state->width * state->height);
456 * We only store (x,y) pairs in todo, but it's easier to reuse
457 * xyd_cmp and just store direction 0 every time.
459 todo = newtree234(xyd_cmp);
460 add234(todo, new_xyd(state->width / 2, state->height / 2, 0));
462 while ( (xyd = delpos234(todo, 0)) != NULL) {
463 int x1, y1, d1, x2, y2, d2;
469 for (d1 = 1; d1 < 0x10; d1 <<= 1) {
470 OFFSET(x2, y2, x1, y1, d1, state);
474 * If the next tile in this direction is connected to
475 * us, and there isn't a barrier in the way, and it
476 * isn't already marked active, then mark it active and
477 * add it to the to-examine list.
479 if ((tile(state, x1, y1) & d1) &&
480 (tile(state, x2, y2) & d2) &&
481 !(barrier(state, x1, y1) & d1) &&
482 !index(state, active, x2, y2)) {
483 index(state, active, x2, y2) = 1;
484 add234(todo, new_xyd(x2, y2, 0));
488 /* Now we expect the todo list to have shrunk to zero size. */
489 assert(count234(todo) == 0);
495 /* ----------------------------------------------------------------------
498 game_state *make_move(game_state *state, int x, int y, int button)
504 * All moves in Net are made with the mouse.
506 if (button != LEFT_BUTTON &&
507 button != MIDDLE_BUTTON &&
508 button != RIGHT_BUTTON)
512 * The button must have been clicked on a valid tile.
520 if (tx >= state->width || ty >= state->height)
522 if (tx % TILE_SIZE >= TILE_SIZE - TILE_BORDER ||
523 ty % TILE_SIZE >= TILE_SIZE - TILE_BORDER)
527 * The middle button locks or unlocks a tile. (A locked tile
528 * cannot be turned, and is visually marked as being locked.
529 * This is a convenience for the player, so that once they are
530 * sure which way round a tile goes, they can lock it and thus
531 * avoid forgetting later on that they'd already done that one;
532 * and the locking also prevents them turning the tile by
533 * accident. If they change their mind, another middle click
536 if (button == MIDDLE_BUTTON) {
537 ret = dup_game(state);
538 tile(ret, tx, ty) ^= LOCKED;
543 * The left and right buttons have no effect if clicked on a
546 if (tile(state, tx, ty) & LOCKED)
550 * Otherwise, turn the tile one way or the other. Left button
551 * turns anticlockwise; right button turns clockwise.
553 ret = dup_game(state);
554 orig = tile(ret, tx, ty);
555 if (button == LEFT_BUTTON)
556 tile(ret, tx, ty) = A(orig);
558 tile(ret, tx, ty) = C(orig);
561 * Check whether the game has been completed.
564 unsigned char *active = compute_active(ret);
568 for (x1 = 0; x1 < ret->width; x1++)
569 for (y1 = 0; y1 < ret->height; y1++)
570 if (!index(ret, active, x1, y1)) {
572 goto break_label; /* break out of two loops at once */
579 ret->completed = TRUE;
585 /* ----------------------------------------------------------------------
586 * Routines for drawing the game position on the screen.
589 #ifndef TESTMODE /* FIXME: should be #ifdef */
593 game_params params = { 13, 11, TRUE, 0.1 };
596 unsigned char *active;
599 state = new_game(¶ms, seed);
600 active = compute_active(state);
605 printf("\033)0\016");
606 for (y = 0; y < state->height; y++) {
607 for (x = 0; x < state->width; x++) {
608 if (index(state, active, x, y))
609 printf("\033[1;32m");
611 printf("\033[0;31m");
612 putchar("~``m`qjv`lxtkwua"[tile(state, x, y)]);