mdw@git.distorted.org.uk Git - sgt/puzzles/blob - sixteen.c

   1 /*
   2  * sixteen.c: `16-puzzle', a sliding-tiles jigsaw which differs
   3  * from the 15-puzzle in that you toroidally rotate a row or column
   4  * at a time.
   5  */
   6
   7 #include <stdio.h>
   8 #include <stdlib.h>
   9 #include <string.h>
  10 #include <assert.h>
  11 #include <ctype.h>
  12 #include <math.h>
  13
  14 #include "puzzles.h"
  15
  16 #define TILE_SIZE 48
  17 #define BORDER    TILE_SIZE            /* big border to fill with arrows */
  18 #define HIGHLIGHT_WIDTH (TILE_SIZE / 20)
  19 #define COORD(x)  ( (x) * TILE_SIZE + BORDER )
  20 #define FROMCOORD(x)  ( ((x) - BORDER + 2*TILE_SIZE) / TILE_SIZE - 2 )
  21
  22 #define ANIM_TIME 0.13F
  23 #define FLASH_FRAME 0.13F
  24
  25 #define X(state, i) ( (i) % (state)->w )
  26 #define Y(state, i) ( (i) / (state)->w )
  27 #define C(state, x, y) ( (y) * (state)->w + (x) )
  28
  29 enum {
  30     COL_BACKGROUND,
  31     COL_TEXT,
  32     COL_HIGHLIGHT,
  33     COL_LOWLIGHT,
  34     NCOLOURS
  35 };
  36
  37 struct game_params {
  38     int w, h;
  39 };
  40
  41 struct game_state {
  42     int w, h, n;
  43     int *tiles;
  44     int completed;
  45     int just_used_solve;               /* used to suppress undo animation */
  46     int used_solve;                    /* used to suppress completion flash */
  47     int movecount;
  48     int last_movement_sense;
  49 };
  50
  51 static game_params *default_params(void)
  52 {
  53     game_params *ret = snew(game_params);
  54
  55     ret->w = ret->h = 4;
  56
  57     return ret;
  58 }
  59
  60 static int game_fetch_preset(int i, char **name, game_params **params)
  61 {
  62     game_params *ret;
  63     int w, h;
  64     char buf[80];
  65
  66     switch (i) {
  67       case 0: w = 3, h = 3; break;
  68       case 1: w = 4, h = 3; break;
  69       case 2: w = 4, h = 4; break;
  70       case 3: w = 5, h = 4; break;
  71       case 4: w = 5, h = 5; break;
  72       default: return FALSE;
  73     }
  74
  75     sprintf(buf, "%dx%d", w, h);
  76     *name = dupstr(buf);
  77     *params = ret = snew(game_params);
  78     ret->w = w;
  79     ret->h = h;
  80     return TRUE;
  81 }
  82
  83 static void free_params(game_params *params)
  84 {
  85     sfree(params);
  86 }
  87
  88 static game_params *dup_params(game_params *params)
  89 {
  90     game_params *ret = snew(game_params);
  91     *ret = *params;                    /* structure copy */
  92     return ret;
  93 }
  94
  95 static game_params *decode_params(char const *string)
  96 {
  97     game_params *ret = default_params();
  98
  99     ret->w = ret->h = atoi(string);
 100     while (*string && isdigit(*string)) string++;
 101     if (*string == 'x') {
 102         string++;
 103         ret->h = atoi(string);
 104     }
 105
 106     return ret;
 107 }
 108
 109 static char *encode_params(game_params *params)
 110 {
 111     char data[256];
 112
 113     sprintf(data, "%dx%d", params->w, params->h);
 114
 115     return dupstr(data);
 116 }
 117
 118 static config_item *game_configure(game_params *params)
 119 {
 120     config_item *ret;
 121     char buf[80];
 122
 123     ret = snewn(3, config_item);
 124
 125     ret[0].name = "Width";
 126     ret[0].type = C_STRING;
 127     sprintf(buf, "%d", params->w);
 128     ret[0].sval = dupstr(buf);
 129     ret[0].ival = 0;
 130
 131     ret[1].name = "Height";
 132     ret[1].type = C_STRING;
 133     sprintf(buf, "%d", params->h);
 134     ret[1].sval = dupstr(buf);
 135     ret[1].ival = 0;
 136
 137     ret[2].name = NULL;
 138     ret[2].type = C_END;
 139     ret[2].sval = NULL;
 140     ret[2].ival = 0;
 141
 142     return ret;
 143 }
 144
 145 static game_params *custom_params(config_item *cfg)
 146 {
 147     game_params *ret = snew(game_params);
 148
 149     ret->w = atoi(cfg[0].sval);
 150     ret->h = atoi(cfg[1].sval);
 151
 152     return ret;
 153 }
 154
 155 static char *validate_params(game_params *params)
 156 {
 157     if (params->w < 2 && params->h < 2)
 158         return "Width and height must both be at least two";
 159
 160     return NULL;
 161 }
 162
 163 static int perm_parity(int *perm, int n)
 164 {
 165     int i, j, ret;
 166
 167     ret = 0;
 168
 169     for (i = 0; i < n-1; i++)
 170         for (j = i+1; j < n; j++)
 171             if (perm[i] > perm[j])
 172                 ret = !ret;
 173
 174     return ret;
 175 }
 176
 177 static char *new_game_seed(game_params *params, random_state *rs,
 178                            game_aux_info **aux)
 179 {
 180     int stop, n, i, x;
 181     int x1, x2, p1, p2;
 182     int *tiles, *used;
 183     char *ret;
 184     int retlen;
 185
 186     n = params->w * params->h;
 187
 188     tiles = snewn(n, int);
 189     used = snewn(n, int);
 190
 191     for (i = 0; i < n; i++) {
 192         tiles[i] = -1;
 193         used[i] = FALSE;
 194     }
 195
 196     /*
 197      * If both dimensions are odd, there is a parity constraint.
 198      */
 199     if (params->w & params->h & 1)
 200         stop = 2;
 201     else
 202         stop = 0;
 203
 204     /*
 205      * Place everything except (possibly) the last two tiles.
 206      */
 207     for (x = 0, i = n; i > stop; i--) {
 208         int k = i > 1 ? random_upto(rs, i) : 0;
 209         int j;
 210
 211         for (j = 0; j < n; j++)
 212             if (!used[j] && (k-- == 0))
 213                 break;
 214
 215         assert(j < n && !used[j]);
 216         used[j] = TRUE;
 217
 218         while (tiles[x] >= 0)
 219             x++;
 220         assert(x < n);
 221         tiles[x] = j;
 222     }
 223
 224     if (stop) {
 225         /*
 226          * Find the last two locations, and the last two pieces.
 227          */
 228         while (tiles[x] >= 0)
 229             x++;
 230         assert(x < n);
 231         x1 = x;
 232         x++;
 233         while (tiles[x] >= 0)
 234             x++;
 235         assert(x < n);
 236         x2 = x;
 237
 238         for (i = 0; i < n; i++)
 239             if (!used[i])
 240                 break;
 241         p1 = i;
 242         for (i = p1+1; i < n; i++)
 243             if (!used[i])
 244                 break;
 245         p2 = i;
 246
 247         /*
 248          * Try the last two tiles one way round. If that fails, swap
 249          * them.
 250          */
 251         tiles[x1] = p1;
 252         tiles[x2] = p2;
 253         if (perm_parity(tiles, n) != 0) {
 254             tiles[x1] = p2;
 255             tiles[x2] = p1;
 256             assert(perm_parity(tiles, n) == 0);
 257         }
 258     }
 259
 260     /*
 261      * Now construct the game seed, by describing the tile array as
 262      * a simple sequence of comma-separated integers.
 263      */
 264     ret = NULL;
 265     retlen = 0;
 266     for (i = 0; i < n; i++) {
 267         char buf[80];
 268         int k;
 269
 270         k = sprintf(buf, "%d,", tiles[i]+1);
 271
 272         ret = sresize(ret, retlen + k + 1, char);
 273         strcpy(ret + retlen, buf);
 274         retlen += k;
 275     }
 276     ret[retlen-1] = '\0';              /* delete last comma */
 277
 278     sfree(tiles);
 279     sfree(used);
 280
 281     return ret;
 282 }
 283
 284 static void game_free_aux_info(game_aux_info *aux)
 285 {
 286     assert(!"Shouldn't happen");
 287 }
 288
 289
 290 static char *validate_seed(game_params *params, char *seed)
 291 {
 292     char *p, *err;
 293     int i, area;
 294     int *used;
 295
 296     area = params->w * params->h;
 297     p = seed;
 298     err = NULL;
 299
 300     used = snewn(area, int);
 301     for (i = 0; i < area; i++)
 302         used[i] = FALSE;
 303
 304     for (i = 0; i < area; i++) {
 305         char *q = p;
 306         int n;
 307
 308         if (*p < '0' || *p > '9') {
 309             err = "Not enough numbers in string";
 310             goto leave;
 311         }
 312         while (*p >= '0' && *p <= '9')
 313             p++;
 314         if (i < area-1 && *p != ',') {
 315             err = "Expected comma after number";
 316             goto leave;
 317         }
 318         else if (i == area-1 && *p) {
 319             err = "Excess junk at end of string";
 320             goto leave;
 321         }
 322         n = atoi(q);
 323         if (n < 1 || n > area) {
 324             err = "Number out of range";
 325             goto leave;
 326         }
 327         if (used[n-1]) {
 328             err = "Number used twice";
 329             goto leave;
 330         }
 331         used[n-1] = TRUE;
 332
 333         if (*p) p++;                   /* eat comma */
 334     }
 335
 336     leave:
 337     sfree(used);
 338     return err;
 339 }
 340
 341 static game_state *new_game(game_params *params, char *seed)
 342 {
 343     game_state *state = snew(game_state);
 344     int i;
 345     char *p;
 346
 347     state->w = params->w;
 348     state->h = params->h;
 349     state->n = params->w * params->h;
 350     state->tiles = snewn(state->n, int);
 351
 352     p = seed;
 353     i = 0;
 354     for (i = 0; i < state->n; i++) {
 355         assert(*p);
 356         state->tiles[i] = atoi(p);
 357         while (*p && *p != ',')
 358             p++;
 359         if (*p) p++;                   /* eat comma */
 360     }
 361     assert(!*p);
 362
 363     state->completed = state->movecount = 0;
 364     state->used_solve = state->just_used_solve = FALSE;
 365     state->last_movement_sense = 0;
 366
 367     return state;
 368 }
 369
 370 static game_state *dup_game(game_state *state)
 371 {
 372     game_state *ret = snew(game_state);
 373
 374     ret->w = state->w;
 375     ret->h = state->h;
 376     ret->n = state->n;
 377     ret->tiles = snewn(state->w * state->h, int);
 378     memcpy(ret->tiles, state->tiles, state->w * state->h * sizeof(int));
 379     ret->completed = state->completed;
 380     ret->movecount = state->movecount;
 381     ret->used_solve = state->used_solve;
 382     ret->just_used_solve = state->just_used_solve;
 383     ret->last_movement_sense = state->last_movement_sense;
 384
 385     return ret;
 386 }
 387
 388 static void free_game(game_state *state)
 389 {
 390     sfree(state);
 391 }
 392
 393 static game_state *solve_game(game_state *state, game_aux_info *aux,
 394                               char **error)
 395 {
 396     game_state *ret = dup_game(state);
 397     int i;
 398
 399     /*
 400      * Simply replace the grid with a solved one. For this game,
 401      * this isn't a useful operation for actually telling the user
 402      * what they should have done, but it is useful for
 403      * conveniently being able to get hold of a clean state from
 404      * which to practise manoeuvres.
 405      */
 406     for (i = 0; i < ret->n; i++)
 407         ret->tiles[i] = i+1;
 408     ret->used_solve = ret->just_used_solve = TRUE;
 409     ret->completed = ret->movecount = 1;
 410
 411     return ret;
 412 }
 413
 414 static char *game_text_format(game_state *state)
 415 {
 416     char *ret, *p, buf[80];
 417     int x, y, col, maxlen;
 418
 419     /*
 420      * First work out how many characters we need to display each
 421      * number.
 422      */
 423     col = sprintf(buf, "%d", state->n);
 424
 425     /*
 426      * Now we know the exact total size of the grid we're going to
 427      * produce: it's got h rows, each containing w lots of col, w-1
 428      * spaces and a trailing newline.
 429      */
 430     maxlen = state->h * state->w * (col+1);
 431
 432     ret = snewn(maxlen+1, char);
 433     p = ret;
 434
 435     for (y = 0; y < state->h; y++) {
 436         for (x = 0; x < state->w; x++) {
 437             int v = state->tiles[state->w*y+x];
 438             sprintf(buf, "%*d", col, v);
 439             memcpy(p, buf, col);
 440             p += col;
 441             if (x+1 == state->w)
 442                 *p++ = '\n';
 443             else
 444                 *p++ = ' ';
 445         }
 446     }
 447
 448     assert(p - ret == maxlen);
 449     *p = '\0';
 450     return ret;
 451 }
 452
 453 static game_ui *new_ui(game_state *state)
 454 {
 455     return NULL;
 456 }
 457
 458 static void free_ui(game_ui *ui)
 459 {
 460 }
 461
 462 static game_state *make_move(game_state *from, game_ui *ui,
 463                              int x, int y, int button)
 464 {
 465     int cx, cy;
 466     int dx, dy, tx, ty, n;
 467     game_state *ret;
 468
 469     if (button != LEFT_BUTTON && button != RIGHT_BUTTON)
 470         return NULL;
 471
 472     cx = FROMCOORD(x);
 473     cy = FROMCOORD(y);
 474     if (cx == -1 && cy >= 0 && cy < from->h)
 475         n = from->w, dx = +1, dy = 0;
 476     else if (cx == from->w && cy >= 0 && cy < from->h)
 477         n = from->w, dx = -1, dy = 0;
 478     else if (cy == -1 && cx >= 0 && cx < from->w)
 479         n = from->h, dy = +1, dx = 0;
 480     else if (cy == from->h && cx >= 0 && cx < from->w)
 481         n = from->h, dy = -1, dx = 0;
 482     else
 483         return NULL;                   /* invalid click location */
 484
 485     /* reverse direction if right hand button is pressed */
 486     if (button == RIGHT_BUTTON)
 487     {
 488         dx = -dx; if (dx) cx = from->w - 1 - cx;
 489         dy = -dy; if (dy) cy = from->h - 1 - cy;
 490     }
 491
 492     ret = dup_game(from);
 493     ret->just_used_solve = FALSE;      /* zero this in a hurry */
 494
 495     do {
 496         cx += dx;
 497         cy += dy;
 498         tx = (cx + dx + from->w) % from->w;
 499         ty = (cy + dy + from->h) % from->h;
 500         ret->tiles[C(ret, cx, cy)] = from->tiles[C(from, tx, ty)];
 501     } while (--n > 0);
 502
 503     ret->movecount++;
 504
 505     ret->last_movement_sense = -(dx+dy);
 506
 507     /*
 508      * See if the game has been completed.
 509      */
 510     if (!ret->completed) {
 511         ret->completed = ret->movecount;
 512         for (n = 0; n < ret->n; n++)
 513             if (ret->tiles[n] != n+1)
 514                 ret->completed = FALSE;
 515     }
 516
 517     return ret;
 518 }
 519
 520 /* ----------------------------------------------------------------------
 521  * Drawing routines.
 522  */
 523
 524 struct game_drawstate {
 525     int started;
 526     int w, h, bgcolour;
 527     int *tiles;
 528 };
 529
 530 static void game_size(game_params *params, int *x, int *y)
 531 {
 532     *x = TILE_SIZE * params->w + 2 * BORDER;
 533     *y = TILE_SIZE * params->h + 2 * BORDER;
 534 }
 535
 536 static float *game_colours(frontend *fe, game_state *state, int *ncolours)
 537 {
 538     float *ret = snewn(3 * NCOLOURS, float);
 539     int i;
 540     float max;
 541
 542     frontend_default_colour(fe, &ret[COL_BACKGROUND * 3]);
 543
 544     /*
 545      * Drop the background colour so that the highlight is
 546      * noticeably brighter than it while still being under 1.
 547      */
 548     max = ret[COL_BACKGROUND*3];
 549     for (i = 1; i < 3; i++)
 550         if (ret[COL_BACKGROUND*3+i] > max)
 551             max = ret[COL_BACKGROUND*3+i];
 552     if (max * 1.2F > 1.0F) {
 553         for (i = 0; i < 3; i++)
 554             ret[COL_BACKGROUND*3+i] /= (max * 1.2F);
 555     }
 556
 557     for (i = 0; i < 3; i++) {
 558         ret[COL_HIGHLIGHT * 3 + i] = ret[COL_BACKGROUND * 3 + i] * 1.2F;
 559         ret[COL_LOWLIGHT * 3 + i] = ret[COL_BACKGROUND * 3 + i] * 0.8F;
 560         ret[COL_TEXT * 3 + i] = 0.0;
 561     }
 562
 563     *ncolours = NCOLOURS;
 564     return ret;
 565 }
 566
 567 static game_drawstate *game_new_drawstate(game_state *state)
 568 {
 569     struct game_drawstate *ds = snew(struct game_drawstate);
 570     int i;
 571
 572     ds->started = FALSE;
 573     ds->w = state->w;
 574     ds->h = state->h;
 575     ds->bgcolour = COL_BACKGROUND;
 576     ds->tiles = snewn(ds->w*ds->h, int);
 577     for (i = 0; i < ds->w*ds->h; i++)
 578         ds->tiles[i] = -1;
 579
 580     return ds;
 581 }
 582
 583 static void game_free_drawstate(game_drawstate *ds)
 584 {
 585     sfree(ds->tiles);
 586     sfree(ds);
 587 }
 588
 589 static void draw_tile(frontend *fe, game_state *state, int x, int y,
 590                       int tile, int flash_colour)
 591 {
 592     if (tile == 0) {
 593         draw_rect(fe, x, y, TILE_SIZE, TILE_SIZE,
 594                   flash_colour);
 595     } else {
 596         int coords[6];
 597         char str[40];
 598
 599         coords[0] = x + TILE_SIZE - 1;
 600         coords[1] = y + TILE_SIZE - 1;
 601         coords[2] = x + TILE_SIZE - 1;
 602         coords[3] = y;
 603         coords[4] = x;
 604         coords[5] = y + TILE_SIZE - 1;
 605         draw_polygon(fe, coords, 3, TRUE, COL_LOWLIGHT);
 606         draw_polygon(fe, coords, 3, FALSE, COL_LOWLIGHT);
 607
 608         coords[0] = x;
 609         coords[1] = y;
 610         draw_polygon(fe, coords, 3, TRUE, COL_HIGHLIGHT);
 611         draw_polygon(fe, coords, 3, FALSE, COL_HIGHLIGHT);
 612
 613         draw_rect(fe, x + HIGHLIGHT_WIDTH, y + HIGHLIGHT_WIDTH,
 614                   TILE_SIZE - 2*HIGHLIGHT_WIDTH, TILE_SIZE - 2*HIGHLIGHT_WIDTH,
 615                   flash_colour);
 616
 617         sprintf(str, "%d", tile);
 618         draw_text(fe, x + TILE_SIZE/2, y + TILE_SIZE/2,
 619                   FONT_VARIABLE, TILE_SIZE/3, ALIGN_VCENTRE | ALIGN_HCENTRE,
 620                   COL_TEXT, str);
 621     }
 622     draw_update(fe, x, y, TILE_SIZE, TILE_SIZE);
 623 }
 624
 625 static void draw_arrow(frontend *fe, int x, int y, int xdx, int xdy)
 626 {
 627     int coords[14];
 628     int ydy = -xdx, ydx = xdy;
 629
 630 #define POINT(n, xx, yy) ( \
 631     coords[2*(n)+0] = x + (xx)*xdx + (yy)*ydx, \
 632     coords[2*(n)+1] = y + (xx)*xdy + (yy)*ydy)
 633
 634     POINT(0, TILE_SIZE / 2, 3 * TILE_SIZE / 4);   /* top of arrow */
 635     POINT(1, 3 * TILE_SIZE / 4, TILE_SIZE / 2);   /* right corner */
 636     POINT(2, 5 * TILE_SIZE / 8, TILE_SIZE / 2);   /* right concave */
 637     POINT(3, 5 * TILE_SIZE / 8, TILE_SIZE / 4);   /* bottom right */
 638     POINT(4, 3 * TILE_SIZE / 8, TILE_SIZE / 4);   /* bottom left */
 639     POINT(5, 3 * TILE_SIZE / 8, TILE_SIZE / 2);   /* left concave */
 640     POINT(6,     TILE_SIZE / 4, TILE_SIZE / 2);   /* left corner */
 641
 642     draw_polygon(fe, coords, 7, TRUE, COL_LOWLIGHT);
 643     draw_polygon(fe, coords, 7, FALSE, COL_TEXT);
 644 }
 645
 646 static void game_redraw(frontend *fe, game_drawstate *ds, game_state *oldstate,
 647                  game_state *state, int dir, game_ui *ui,
 648                  float animtime, float flashtime)
 649 {
 650     int i, bgcolour;
 651
 652     if (flashtime > 0) {
 653         int frame = (int)(flashtime / FLASH_FRAME);
 654         bgcolour = (frame % 2 ? COL_LOWLIGHT : COL_HIGHLIGHT);
 655     } else
 656         bgcolour = COL_BACKGROUND;
 657
 658     if (!ds->started) {
 659         int coords[6];
 660
 661         draw_rect(fe, 0, 0,
 662                   TILE_SIZE * state->w + 2 * BORDER,
 663                   TILE_SIZE * state->h + 2 * BORDER, COL_BACKGROUND);
 664         draw_update(fe, 0, 0,
 665                     TILE_SIZE * state->w + 2 * BORDER,
 666                     TILE_SIZE * state->h + 2 * BORDER);
 667
 668         /*
 669          * Recessed area containing the whole puzzle.
 670          */
 671         coords[0] = COORD(state->w) + HIGHLIGHT_WIDTH - 1;
 672         coords[1] = COORD(state->h) + HIGHLIGHT_WIDTH - 1;
 673         coords[2] = COORD(state->w) + HIGHLIGHT_WIDTH - 1;
 674         coords[3] = COORD(0) - HIGHLIGHT_WIDTH;
 675         coords[4] = COORD(0) - HIGHLIGHT_WIDTH;
 676         coords[5] = COORD(state->h) + HIGHLIGHT_WIDTH - 1;
 677         draw_polygon(fe, coords, 3, TRUE, COL_HIGHLIGHT);
 678         draw_polygon(fe, coords, 3, FALSE, COL_HIGHLIGHT);
 679
 680         coords[1] = COORD(0) - HIGHLIGHT_WIDTH;
 681         coords[0] = COORD(0) - HIGHLIGHT_WIDTH;
 682         draw_polygon(fe, coords, 3, TRUE, COL_LOWLIGHT);
 683         draw_polygon(fe, coords, 3, FALSE, COL_LOWLIGHT);
 684
 685         /*
 686          * Arrows for making moves.
 687          */
 688         for (i = 0; i < state->w; i++) {
 689             draw_arrow(fe, COORD(i), COORD(0), +1, 0);
 690             draw_arrow(fe, COORD(i+1), COORD(state->h), -1, 0);
 691         }
 692         for (i = 0; i < state->h; i++) {
 693             draw_arrow(fe, COORD(state->w), COORD(i), 0, +1);
 694             draw_arrow(fe, COORD(0), COORD(i+1), 0, -1);
 695         }
 696
 697         ds->started = TRUE;
 698     }
 699
 700     /*
 701      * Now draw each tile.
 702      */
 703
 704     clip(fe, COORD(0), COORD(0), TILE_SIZE*state->w, TILE_SIZE*state->h);
 705
 706     for (i = 0; i < state->n; i++) {
 707         int t, t0;
 708         /*
 709          * Figure out what should be displayed at this
 710          * location. It's either a simple tile, or it's a
 711          * transition between two tiles (in which case we say
 712          * -1 because it must always be drawn).
 713          */
 714
 715         if (oldstate && oldstate->tiles[i] != state->tiles[i])
 716             t = -1;
 717         else
 718             t = state->tiles[i];
 719
 720         t0 = t;
 721
 722         if (ds->bgcolour != bgcolour ||   /* always redraw when flashing */
 723             ds->tiles[i] != t || ds->tiles[i] == -1 || t == -1) {
 724             int x, y, x2, y2;
 725
 726             /*
 727              * Figure out what to _actually_ draw, and where to
 728              * draw it.
 729              */
 730             if (t == -1) {
 731                 int x0, y0, x1, y1, dx, dy;
 732                 int j;
 733                 float c;
 734                 int sense;
 735
 736                 if (dir < 0) {
 737                     assert(oldstate);
 738                     sense = -oldstate->last_movement_sense;
 739                 } else {
 740                     sense = state->last_movement_sense;
 741                 }
 742
 743                 t = state->tiles[i];
 744
 745                 /*
 746                  * FIXME: must be prepared to draw a double
 747                  * tile in some situations.
 748                  */
 749
 750                 /*
 751                  * Find the coordinates of this tile in the old and
 752                  * new states.
 753                  */
 754                 x1 = COORD(X(state, i));
 755                 y1 = COORD(Y(state, i));
 756                 for (j = 0; j < oldstate->n; j++)
 757                     if (oldstate->tiles[j] == state->tiles[i])
 758                         break;
 759                 assert(j < oldstate->n);
 760                 x0 = COORD(X(state, j));
 761                 y0 = COORD(Y(state, j));
 762
 763                 dx = (x1 - x0);
 764                 if (dx != 0 &&
 765                     dx != TILE_SIZE * sense) {
 766                     dx = (dx < 0 ? dx + TILE_SIZE * state->w :
 767                           dx - TILE_SIZE * state->w);
 768                     assert(abs(dx) == TILE_SIZE);
 769                 }
 770                 dy = (y1 - y0);
 771                 if (dy != 0 &&
 772                     dy != TILE_SIZE * sense) {
 773                     dy = (dy < 0 ? dy + TILE_SIZE * state->h :
 774                           dy - TILE_SIZE * state->h);
 775                     assert(abs(dy) == TILE_SIZE);
 776                 }
 777
 778                 c = (animtime / ANIM_TIME);
 779                 if (c < 0.0F) c = 0.0F;
 780                 if (c > 1.0F) c = 1.0F;
 781
 782                 x = x0 + (int)(c * dx);
 783                 y = y0 + (int)(c * dy);
 784                 x2 = x1 - dx + (int)(c * dx);
 785                 y2 = y1 - dy + (int)(c * dy);
 786             } else {
 787                 x = COORD(X(state, i));
 788                 y = COORD(Y(state, i));
 789                 x2 = y2 = -1;
 790             }
 791
 792             draw_tile(fe, state, x, y, t, bgcolour);
 793             if (x2 != -1 || y2 != -1)
 794                 draw_tile(fe, state, x2, y2, t, bgcolour);
 795         }
 796         ds->tiles[i] = t0;
 797     }
 798
 799     unclip(fe);
 800
 801     ds->bgcolour = bgcolour;
 802
 803     /*
 804      * Update the status bar.
 805      */
 806     {
 807         char statusbuf[256];
 808
 809         /*
 810          * Don't show the new status until we're also showing the
 811          * new _state_ - after the game animation is complete.
 812          */
 813         if (oldstate)
 814             state = oldstate;
 815
 816         if (state->used_solve)
 817             sprintf(statusbuf, "Moves since auto-solve: %d",
 818                     state->movecount - state->completed);
 819         else
 820             sprintf(statusbuf, "%sMoves: %d",
 821                     (state->completed ? "COMPLETED! " : ""),
 822                     (state->completed ? state->completed : state->movecount));
 823
 824         status_bar(fe, statusbuf);
 825     }
 826 }
 827
 828 static float game_anim_length(game_state *oldstate,
 829                               game_state *newstate, int dir)
 830 {
 831     if ((dir > 0 && newstate->just_used_solve) ||
 832         (dir < 0 && oldstate->just_used_solve))
 833         return 0.0F;
 834     else
 835         return ANIM_TIME;
 836 }
 837
 838 static float game_flash_length(game_state *oldstate,
 839                                game_state *newstate, int dir)
 840 {
 841     if (!oldstate->completed && newstate->completed &&
 842         !oldstate->used_solve && !newstate->used_solve)
 843         return 2 * FLASH_FRAME;
 844     else
 845         return 0.0F;
 846 }
 847
 848 static int game_wants_statusbar(void)
 849 {
 850     return TRUE;
 851 }
 852
 853 #ifdef COMBINED
 854 #define thegame sixteen
 855 #endif
 856
 857 const struct game thegame = {
 858     "Sixteen", "games.sixteen",
 859     default_params,
 860     game_fetch_preset,
 861     decode_params,
 862     encode_params,
 863     free_params,
 864     dup_params,
 865     TRUE, game_configure, custom_params,
 866     validate_params,
 867     new_game_seed,
 868     game_free_aux_info,
 869     validate_seed,
 870     new_game,
 871     dup_game,
 872     free_game,
 873     TRUE, solve_game,
 874     TRUE, game_text_format,
 875     new_ui,
 876     free_ui,
 877     make_move,
 878     game_size,
 879     game_colours,
 880     game_new_drawstate,
 881     game_free_drawstate,
 882     game_redraw,
 883     game_anim_length,
 884     game_flash_length,
 885     game_wants_statusbar,
 886 };