File: samegame.c

package info (click to toggle)
sgt-puzzles 6879-1
  • links: PTS
  • area: main
  • in suites: etch, etch-m68k
  • size: 2,780 kB
  • ctags: 3,974
  • sloc: ansic: 41,479; perl: 1,260; objc: 1,184; makefile: 50
file content (1663 lines) | stat: -rw-r--r-- 48,539 bytes parent folder | download
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
/*
 * 'same game' -- try to remove all the coloured squares by
 *                selecting regions of contiguous colours.
 */

/*
 * TODO on grid generation:
 * 
 *  - Generation speed could still be improved.
 *     * 15x10c3 is the only really difficult one of the existing
 *       presets. The others are all either small enough, or have
 *       the great flexibility given by four colours, that they
 *       don't take long at all.
 *     * I still suspect many problems arise from separate
 * 	 subareas. I wonder if we can also somehow prioritise left-
 * 	 or rightmost insertions so as to avoid area splitting at
 * 	 all where feasible? It's not easy, though, because the
 * 	 current shuffle-then-try-all-options approach to move
 * 	 choice doesn't leave room for `soft' probabilistic
 * 	 prioritisation: we either try all class A moves before any
 * 	 class B ones, or we don't.
 *
 *  - The current generation algorithm inserts exactly two squares
 *    at a time, with a single exception at the beginning of
 *    generation for grids of odd overall size. An obvious
 *    extension would be to permit larger inverse moves during
 *    generation.
 *     * this might reduce the number of failed generations by
 *       making the insertion algorithm more flexible
 *     * on the other hand, it would be significantly more complex
 *     * if I do this I'll need to take out the odd-subarea
 *       avoidance
 *     * a nice feature of the current algorithm is that the
 *       computer's `intended' solution always receives the minimum
 *       possible score, so that pretty much the player's entire
 *       score represents how much better they did than the
 *       computer.
 *
 *  - Is it possible we can _temporarily_ tolerate neighbouring
 *    squares of the same colour, until we've finished setting up
 *    our inverse move?
 *     * or perhaps even not choose the colour of our inserted
 *       region until we have finished placing it, and _then_ look
 *       at what colours border on it?
 *     * I don't think this is currently meaningful unless we're
 *       placing more than a domino at a time.
 *
 *  - possibly write out a full solution so that Solve can somehow
 *    show it step by step?
 *     * aux_info would have to encode the click points
 *     * solve_game() would have to encode not only those click
 * 	 points but also give a move string which reconstructed the
 * 	 initial state
 *     * the game_state would include a pointer to a solution move
 * 	 list, plus an index into that list
 *     * game_changed_state would auto-select the next move if
 * 	 handed a new state which had a solution move list active
 *     * execute_move, if passed such a state as input, would check
 * 	 to see whether the move being made was the same as the one
 * 	 stated by the solution, and if so would advance the move
 * 	 index. Failing that it would return a game_state without a
 * 	 solution move list active at all.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <ctype.h>
#include <math.h>

#include "puzzles.h"

#define TILE_INNER (ds->tileinner)
#define TILE_GAP (ds->tilegap)
#define TILE_SIZE (TILE_INNER + TILE_GAP)
#define PREFERRED_TILE_SIZE 32
#define BORDER (TILE_SIZE / 2)
#define HIGHLIGHT_WIDTH 2

#define FLASH_FRAME 0.13F

#define COORD(x)  ( (x) * TILE_SIZE + BORDER )
#define FROMCOORD(x)  ( ((x) - BORDER + TILE_SIZE) / TILE_SIZE - 1 )

#define X(state, i) ( (i) % (state)->params.w )
#define Y(state, i) ( (i) / (state)->params.w )
#define C(state, x, y) ( (y) * (state)->w + (x) )

enum {
    COL_BACKGROUND,
    COL_1, COL_2, COL_3, COL_4, COL_5, COL_6, COL_7, COL_8, COL_9,
    COL_IMPOSSIBLE, COL_SEL, COL_HIGHLIGHT, COL_LOWLIGHT,
    NCOLOURS
};

/* scoresub is 1 or 2 (for (n-1)^2 or (n-2)^2) */
struct game_params {
    int w, h, ncols, scoresub;
    int soluble;		       /* choose generation algorithm */
};

/* These flags must be unique across all uses; in the game_state,
 * the game_ui, and the drawstate (as they all get combined in the
 * drawstate). */
#define TILE_COLMASK    0x00ff
#define TILE_SELECTED   0x0100 /* used in ui and drawstate */
#define TILE_JOINRIGHT  0x0200 /* used in drawstate */
#define TILE_JOINDOWN   0x0400 /* used in drawstate */
#define TILE_JOINDIAG   0x0800 /* used in drawstate */
#define TILE_HASSEL     0x1000 /* used in drawstate */
#define TILE_IMPOSSIBLE 0x2000 /* used in drawstate */

#define TILE(gs,x,y) ((gs)->tiles[(gs)->params.w*(y)+(x)])
#define COL(gs,x,y) (TILE(gs,x,y) & TILE_COLMASK)
#define ISSEL(gs,x,y) (TILE(gs,x,y) & TILE_SELECTED)

#define SWAPTILE(gs,x1,y1,x2,y2) do {   \
    int t = TILE(gs,x1,y1);               \
    TILE(gs,x1,y1) = TILE(gs,x2,y2);      \
    TILE(gs,x2,y2) = t;                   \
} while (0)

static int npoints(game_params *params, int nsel)
{
    int sdiff = nsel - params->scoresub;
    return (sdiff > 0) ? sdiff * sdiff : 0;
}

struct game_state {
    struct game_params params;
    int n;
    int *tiles; /* colour only */
    int score;
    int complete, impossible;
};

static game_params *default_params(void)
{
    game_params *ret = snew(game_params);
    ret->w = 5;
    ret->h = 5;
    ret->ncols = 3;
    ret->scoresub = 2;
    ret->soluble = TRUE;
    return ret;
}

static const struct game_params samegame_presets[] = {
    { 5, 5, 3, 2, TRUE },
    { 10, 5, 3, 2, TRUE },
#ifdef SLOW_SYSTEM
    { 10, 10, 3, 2, TRUE },
#else
    { 15, 10, 3, 2, TRUE },
#endif
    { 15, 10, 4, 2, TRUE },
    { 20, 15, 4, 2, TRUE }
};

static int game_fetch_preset(int i, char **name, game_params **params)
{
    game_params *ret;
    char str[80];

    if (i < 0 || i >= lenof(samegame_presets))
	return FALSE;

    ret = snew(game_params);
    *ret = samegame_presets[i];

    sprintf(str, "%dx%d, %d colours", ret->w, ret->h, ret->ncols);

    *name = dupstr(str);
    *params = ret;
    return TRUE;
}

static void free_params(game_params *params)
{
    sfree(params);
}

static game_params *dup_params(game_params *params)
{
    game_params *ret = snew(game_params);
    *ret = *params;		       /* structure copy */
    return ret;
}

static void decode_params(game_params *params, char const *string)
{
    char const *p = string;

    params->w = atoi(p);
    while (*p && isdigit((unsigned char)*p)) p++;
    if (*p == 'x') {
	p++;
	params->h = atoi(p);
	while (*p && isdigit((unsigned char)*p)) p++;
    } else {
	params->h = params->w;
    }
    if (*p == 'c') {
	p++;
	params->ncols = atoi(p);
	while (*p && isdigit((unsigned char)*p)) p++;
    } else {
	params->ncols = 3;
    }
    if (*p == 's') {
	p++;
	params->scoresub = atoi(p);
	while (*p && isdigit((unsigned char)*p)) p++;
    } else {
	params->scoresub = 2;
    }
    if (*p == 'r') {
	p++;
	params->soluble = FALSE;
    }
}

static char *encode_params(game_params *params, int full)
{
    char ret[80];

    sprintf(ret, "%dx%dc%ds%d%s",
	    params->w, params->h, params->ncols, params->scoresub,
	    full && !params->soluble ? "r" : "");
    return dupstr(ret);
}

static config_item *game_configure(game_params *params)
{
    config_item *ret;
    char buf[80];

    ret = snewn(6, config_item);

    ret[0].name = "Width";
    ret[0].type = C_STRING;
    sprintf(buf, "%d", params->w);
    ret[0].sval = dupstr(buf);
    ret[0].ival = 0;

    ret[1].name = "Height";
    ret[1].type = C_STRING;
    sprintf(buf, "%d", params->h);
    ret[1].sval = dupstr(buf);
    ret[1].ival = 0;

    ret[2].name = "No. of colours";
    ret[2].type = C_STRING;
    sprintf(buf, "%d", params->ncols);
    ret[2].sval = dupstr(buf);
    ret[2].ival = 0;

    ret[3].name = "Scoring system";
    ret[3].type = C_CHOICES;
    ret[3].sval = ":(n-1)^2:(n-2)^2";
    ret[3].ival = params->scoresub-1;

    ret[4].name = "Ensure solubility";
    ret[4].type = C_BOOLEAN;
    ret[4].sval = NULL;
    ret[4].ival = params->soluble;

    ret[5].name = NULL;
    ret[5].type = C_END;
    ret[5].sval = NULL;
    ret[5].ival = 0;

    return ret;
}

static game_params *custom_params(config_item *cfg)
{
    game_params *ret = snew(game_params);

    ret->w = atoi(cfg[0].sval);
    ret->h = atoi(cfg[1].sval);
    ret->ncols = atoi(cfg[2].sval);
    ret->scoresub = cfg[3].ival + 1;
    ret->soluble = cfg[4].ival;

    return ret;
}

static char *validate_params(game_params *params, int full)
{
    if (params->w < 1 || params->h < 1)
	return "Width and height must both be positive";

    if (params->ncols > 9)
	return "Maximum of 9 colours";

    if (params->soluble) {
	if (params->ncols < 3)
	    return "Number of colours must be at least three";
	if (params->w * params->h <= 1)
	    return "Grid area must be greater than 1";
    } else {
	if (params->ncols < 2)
	    return "Number of colours must be at least three";
	/* ...and we must make sure we can generate at least 2 squares
	 * of each colour so it's theoretically soluble. */
	if ((params->w * params->h) < (params->ncols * 2))
	    return "Too many colours makes given grid size impossible";
    }

    if ((params->scoresub < 1) || (params->scoresub > 2))
	return "Scoring system not recognised";

    return NULL;
}

/*
 * Guaranteed-soluble grid generator.
 */
static void gen_grid(int w, int h, int nc, int *grid, random_state *rs)
{
    int wh = w*h, tc = nc+1;
    int i, j, k, c, x, y, pos, n;
    int *list, *grid2;
    int ok, failures = 0;

    /*
     * We'll use `list' to track the possible places to put our
     * next insertion. There are up to h places to insert in each
     * column: in a column of height n there are n+1 places because
     * we can insert at the very bottom or the very top, but a
     * column of height h can't have anything at all inserted in it
     * so we have up to h in each column. Likewise, with n columns
     * present there are n+1 places to fit a new one in between but
     * we can't insert a column if there are already w; so there
     * are a maximum of w new columns too. Total is wh + w.
     */
    list = snewn(wh + w, int);
    grid2 = snewn(wh, int);

    do {
        /*
         * Start with two or three squares - depending on parity of w*h
         * - of a random colour.
         */
        for (i = 0; i < wh; i++)
            grid[i] = 0;
        j = 2 + (wh % 2);
        c = 1 + random_upto(rs, nc);
	if (j <= w) {
	    for (i = 0; i < j; i++)
		grid[(h-1)*w+i] = c;
	} else {
	    assert(j <= h);
	    for (i = 0; i < j; i++)
		grid[(h-1-i)*w] = c;
	}

        /*
         * Now repeatedly insert a two-square blob in the grid, of
         * whatever colour will go at the position we chose.
         */
        while (1) {
            n = 0;

            /*
             * Build up a list of insertion points. Each point is
             * encoded as y*w+x; insertion points between columns are
             * encoded as h*w+x.
             */

            if (grid[wh - 1] == 0) {
                /*
                 * The final column is empty, so we can insert new
                 * columns.
                 */
                for (i = 0; i < w; i++) {
                    list[n++] = wh + i;
                    if (grid[(h-1)*w + i] == 0)
                        break;
                }
            }

            /*
             * Now look for places to insert within columns.
             */
            for (i = 0; i < w; i++) {
                if (grid[(h-1)*w+i] == 0)
                    break;		       /* no more columns */

                if (grid[i] != 0)
                    continue;	       /* this column is full */

                for (j = h; j-- > 0 ;) {
                    list[n++] = j*w+i;
                    if (grid[j*w+i] == 0)
                        break;	       /* this column is exhausted */
                }
            }

            if (n == 0)
                break;		       /* we're done */

#ifdef GENERATION_DIAGNOSTICS
            printf("initial grid:\n");
            {
                int x,y;
                for (y = 0; y < h; y++) {
                    for (x = 0; x < w; x++) {
                        if (grid[y*w+x] == 0)
                            printf("-");
                        else
                            printf("%d", grid[y*w+x]);
                    }
                    printf("\n");
                }
            }
#endif

            /*
             * Now go through the list one element at a time in
             * random order, and actually attempt to insert
             * something there.
             */
            while (n-- > 0) {
                int dirs[4], ndirs, dir;

                i = random_upto(rs, n+1);
                pos = list[i];
                list[i] = list[n];

                x = pos % w;
                y = pos / w;

                memcpy(grid2, grid, wh * sizeof(int));

                if (y == h) {
                    /*
                     * Insert a column at position x.
                     */
                    for (i = w-1; i > x; i--)
                        for (j = 0; j < h; j++)
                            grid2[j*w+i] = grid2[j*w+(i-1)];
                    /*
                     * Clear the new column.
                     */
                    for (j = 0; j < h; j++)
                        grid2[j*w+x] = 0;
                    /*
                     * Decrement y so that our first square is actually
                     * inserted _in_ the grid rather than just below it.
                     */
                    y--;
                }

                /*
                 * Insert a square within column x at position y.
                 */
                for (i = 0; i+1 <= y; i++)
                    grid2[i*w+x] = grid2[(i+1)*w+x];

#ifdef GENERATION_DIAGNOSTICS
                printf("trying at n=%d (%d,%d)\n", n, x, y);
                grid2[y*w+x] = tc;
                {
                    int x,y;
                    for (y = 0; y < h; y++) {
                        for (x = 0; x < w; x++) {
                            if (grid2[y*w+x] == 0)
                                printf("-");
                            else if (grid2[y*w+x] <= nc)
                                printf("%d", grid2[y*w+x]);
                            else
                                printf("*");
                        }
                        printf("\n");
                    }
                }
#endif

                /*
                 * Pick our square colour so that it doesn't match any
                 * of its neighbours.
                 */
                {
                    int wrongcol[4], nwrong = 0;

                    /*
                     * List the neighbouring colours.
                     */
                    if (x > 0)
                        wrongcol[nwrong++] = grid2[y*w+(x-1)];
                    if (x+1 < w)
                        wrongcol[nwrong++] = grid2[y*w+(x+1)];
                    if (y > 0)
                        wrongcol[nwrong++] = grid2[(y-1)*w+x];
                    if (y+1 < h)
                        wrongcol[nwrong++] = grid2[(y+1)*w+x];

                    /*
                     * Eliminate duplicates. We can afford a shoddy
                     * algorithm here because the problem size is
                     * bounded.
                     */
                    for (i = j = 0 ;; i++) {
                        int pos = -1, min = 0;
                        if (j > 0)
                            min = wrongcol[j-1];
                        for (k = i; k < nwrong; k++)
                            if (wrongcol[k] > min &&
                                (pos == -1 || wrongcol[k] < wrongcol[pos]))
                                pos = k;
                        if (pos >= 0) {
                            int v = wrongcol[pos];
                            wrongcol[pos] = wrongcol[j];
                            wrongcol[j++] = v;
                        } else
                            break;
                    }
                    nwrong = j;

                    /*
                     * If no colour will go here, stop trying.
                     */
                    if (nwrong == nc)
                        continue;

                    /*
                     * Otherwise, pick a colour from the remaining
                     * ones.
                     */
                    c = 1 + random_upto(rs, nc - nwrong);
                    for (i = 0; i < nwrong; i++) {
                        if (c >= wrongcol[i])
                            c++;
                        else
                            break;
                    }
                }

                /*
                 * Place the new square.
                 * 
                 * Although I've _chosen_ the new region's colour
                 * (so that we can check adjacency), I'm going to
                 * actually place it as an invalid colour (tc)
                 * until I'm sure it's viable. This is so that I
                 * can conveniently check that I really have made a
                 * _valid_ inverse move later on.
                 */
#ifdef GENERATION_DIAGNOSTICS
                printf("picked colour %d\n", c);
#endif
                grid2[y*w+x] = tc;

                /*
                 * Now attempt to extend it in one of three ways: left,
                 * right or up.
                 */
                ndirs = 0;
                if (x > 0 &&
                    grid2[y*w+(x-1)] != c &&
                    grid2[x-1] == 0 &&
                    (y+1 >= h || grid2[(y+1)*w+(x-1)] != c) &&
                    (y+1 >= h || grid2[(y+1)*w+(x-1)] != 0) &&
                    (x <= 1 || grid2[y*w+(x-2)] != c))
                    dirs[ndirs++] = -1;    /* left */
                if (x+1 < w &&
                    grid2[y*w+(x+1)] != c &&
                    grid2[x+1] == 0 &&
                    (y+1 >= h || grid2[(y+1)*w+(x+1)] != c) &&
                    (y+1 >= h || grid2[(y+1)*w+(x+1)] != 0) &&
                    (x+2 >= w || grid2[y*w+(x+2)] != c))
                    dirs[ndirs++] = +1;    /* right */
                if (y > 0 &&
                    grid2[x] == 0 &&
                    (x <= 0 || grid2[(y-1)*w+(x-1)] != c) &&
                    (x+1 >= w || grid2[(y-1)*w+(x+1)] != c)) {
                    /*
                     * We add this possibility _twice_, so that the
                     * probability of placing a vertical domino is
                     * about the same as that of a horizontal. This
                     * should yield less bias in the generated
                     * grids.
                     */
                    dirs[ndirs++] = 0;     /* up */
                    dirs[ndirs++] = 0;     /* up */
                }

                if (ndirs == 0)
                    continue;

                dir = dirs[random_upto(rs, ndirs)];

#ifdef GENERATION_DIAGNOSTICS
                printf("picked dir %d\n", dir);
#endif

                /*
                 * Insert a square within column (x+dir) at position y.
                 */
                for (i = 0; i+1 <= y; i++)
                    grid2[i*w+x+dir] = grid2[(i+1)*w+x+dir];
                grid2[y*w+x+dir] = tc;

                /*
                 * See if we've divided the remaining grid squares
                 * into sub-areas. If so, we need every sub-area to
                 * have an even area or we won't be able to
                 * complete generation.
                 * 
                 * If the height is odd and not all columns are
                 * present, we can increase the area of a subarea
                 * by adding a new column in it, so in that
                 * situation we don't mind having as many odd
                 * subareas as there are spare columns.
                 * 
                 * If the height is even, we can't fix it at all.
                 */
                {
                    int nerrs = 0, nfix = 0;
                    k = 0;             /* current subarea size */
                    for (i = 0; i < w; i++) {
                        if (grid2[(h-1)*w+i] == 0) {
                            if (h % 2)
                                nfix++;
                            continue;
                        }
                        for (j = 0; j < h && grid2[j*w+i] == 0; j++);
                        assert(j < h);
                        if (j == 0) {
                            /*
                             * End of previous subarea.
                             */
                            if (k % 2)
                                nerrs++;
                            k = 0;
                        } else {
                            k += j;
                        }
                    }
                    if (k % 2)
                        nerrs++;
                    if (nerrs > nfix)
                        continue;      /* try a different placement */
                }

                /*
                 * We've made a move. Verify that it is a valid
                 * move and that if made it would indeed yield the
                 * previous grid state. The criteria are:
                 * 
                 *  (a) removing all the squares of colour tc (and
                 *      shuffling the columns up etc) from grid2
                 *      would yield grid
                 *  (b) no square of colour tc is adjacent to one
                 *      of colour c
                 *  (c) all the squares of colour tc form a single
                 *      connected component
                 * 
                 * We verify the latter property at the same time
                 * as checking that removing all the tc squares
                 * would yield the previous grid. Then we colour
                 * the tc squares in colour c by breadth-first
                 * search, which conveniently permits us to test
                 * that they're all connected.
                 */
                {
                    int x1, x2, y1, y2;
                    int ok = TRUE;
                    int fillstart = -1, ntc = 0;

#ifdef GENERATION_DIAGNOSTICS
                    {
                        int x,y;
                        printf("testing move (new, old):\n");
                        for (y = 0; y < h; y++) {
                            for (x = 0; x < w; x++) {
                                if (grid2[y*w+x] == 0)
                                    printf("-");
                                else if (grid2[y*w+x] <= nc)
                                    printf("%d", grid2[y*w+x]);
                                else
                                    printf("*");
                            }
                            printf("   ");
                            for (x = 0; x < w; x++) {
                                if (grid[y*w+x] == 0)
                                    printf("-");
                                else
                                    printf("%d", grid[y*w+x]);
                            }
                            printf("\n");
                        }
                    }
#endif

                    for (x1 = x2 = 0; x2 < w; x2++) {
                        int usedcol = FALSE;

                        for (y1 = y2 = h-1; y2 >= 0; y2--) {
                            if (grid2[y2*w+x2] == tc) {
                                ntc++;
                                if (fillstart == -1)
                                    fillstart = y2*w+x2;
                                if ((y2+1 < h && grid2[(y2+1)*w+x2] == c) ||
                                    (y2-1 >= 0 && grid2[(y2-1)*w+x2] == c) ||
                                    (x2+1 < w && grid2[y2*w+x2+1] == c) ||
                                    (x2-1 >= 0 && grid2[y2*w+x2-1] == c)) {
#ifdef GENERATION_DIAGNOSTICS
                                    printf("adjacency failure at %d,%d\n",
                                           x2, y2);
#endif
                                    ok = FALSE;
                                }
                                continue;
                            }
                            if (grid2[y2*w+x2] == 0)
                                break;
                            usedcol = TRUE;
                            if (grid2[y2*w+x2] != grid[y1*w+x1]) {
#ifdef GENERATION_DIAGNOSTICS
                                printf("matching failure at %d,%d vs %d,%d\n",
                                       x2, y2, x1, y1);
#endif
                                ok = FALSE;
                            }
                            y1--;
                        }

                        /*
                         * If we've reached the top of the column
                         * in grid2, verify that we've also reached
                         * the top of the column in `grid'.
                         */
                        if (usedcol) {
                            while (y1 >= 0) {
                                if (grid[y1*w+x1] != 0) {
#ifdef GENERATION_DIAGNOSTICS
                                    printf("junk at column top (%d,%d)\n",
                                           x1, y1);
#endif
                                    ok = FALSE;
                                }
                                y1--;
                            }
                        }

                        if (!ok)
                            break;

                        if (usedcol)
                            x1++;
                    }

                    if (!ok) {
                        assert(!"This should never happen");

                        /*
                         * If this game is compiled NDEBUG so that
                         * the assertion doesn't bring it to a
                         * crashing halt, the only thing we can do
                         * is to give up, loop round again, and
                         * hope to randomly avoid making whatever
                         * type of move just caused this failure.
                         */
                        continue;
                    }

                    /*
                     * Now use bfs to fill in the tc section as
                     * colour c. We use `list' to store the set of
                     * squares we have to process.
                     */
                    i = j = 0;
                    assert(fillstart >= 0);
                    list[i++] = fillstart;
#ifdef OUTPUT_SOLUTION
                    printf("M");
#endif
                    while (j < i) {
                        k = list[j];
                        x = k % w;
                        y = k / w;
#ifdef OUTPUT_SOLUTION
                        printf("%s%d", j ? "," : "", k);
#endif
                        j++;

                        assert(grid2[k] == tc);
                        grid2[k] = c;

                        if (x > 0 && grid2[k-1] == tc)
                            list[i++] = k-1;
                        if (x+1 < w && grid2[k+1] == tc)
                            list[i++] = k+1;
                        if (y > 0 && grid2[k-w] == tc)
                            list[i++] = k-w;
                        if (y+1 < h && grid2[k+w] == tc)
                            list[i++] = k+w;
                    }
#ifdef OUTPUT_SOLUTION
                    printf("\n");
#endif

                    /*
                     * Check that we've filled the same number of
                     * tc squares as we originally found.
                     */
                    assert(j == ntc);
                }

                memcpy(grid, grid2, wh * sizeof(int));

                break;		       /* done it! */
            }

#ifdef GENERATION_DIAGNOSTICS
            {
                int x,y;
                printf("n=%d\n", n);
                for (y = 0; y < h; y++) {
                    for (x = 0; x < w; x++) {
                        if (grid[y*w+x] == 0)
                            printf("-");
                        else
                            printf("%d", grid[y*w+x]);
                    }
                    printf("\n");
                }
            }
#endif

            if (n < 0)
                break;
        }

        ok = TRUE;
        for (i = 0; i < wh; i++)
            if (grid[i] == 0) {
                ok = FALSE;
                failures++;
#if defined GENERATION_DIAGNOSTICS || defined SHOW_INCOMPLETE
                {
                    int x,y;
                    printf("incomplete grid:\n");
                    for (y = 0; y < h; y++) {
                        for (x = 0; x < w; x++) {
                            if (grid[y*w+x] == 0)
                                printf("-");
                            else
                                printf("%d", grid[y*w+x]);
                        }
                        printf("\n");
                    }
                }
#endif
                break;
            }

    } while (!ok);

#if defined GENERATION_DIAGNOSTICS || defined COUNT_FAILURES
    printf("%d failures\n", failures);
#endif
#ifdef GENERATION_DIAGNOSTICS
    {
        int x,y;
        printf("final grid:\n");
        for (y = 0; y < h; y++) {
            for (x = 0; x < w; x++) {
                printf("%d", grid[y*w+x]);
            }
            printf("\n");
        }
    }
#endif

    sfree(grid2);
    sfree(list);
}

/*
 * Not-guaranteed-soluble grid generator; kept as a legacy, and in
 * case someone finds the slightly odd quality of the guaranteed-
 * soluble grids to be aesthetically displeasing or finds its CPU
 * utilisation to be excessive.
 */
static void gen_grid_random(int w, int h, int nc, int *grid, random_state *rs)
{
    int i, j, c;
    int n = w * h;

    for (i = 0; i < n; i++)
	grid[i] = 0;

    /*
     * Our sole concession to not gratuitously generating insoluble
     * grids is to ensure we have at least two of every colour.
     */
    for (c = 1; c <= nc; c++) {
	for (j = 0; j < 2; j++) {
	    do {
		i = (int)random_upto(rs, n);
	    } while (grid[i] != 0);
	    grid[i] = c;
	}
    }

    /*
     * Fill in the rest of the grid at random.
     */
    for (i = 0; i < n; i++) {
	if (grid[i] == 0)
	    grid[i] = (int)random_upto(rs, nc)+1;
    }
}

static char *new_game_desc(game_params *params, random_state *rs,
			   char **aux, int interactive)
{
    char *ret;
    int n, i, retlen, *tiles;

    n = params->w * params->h;
    tiles = snewn(n, int);

    if (params->soluble)
	gen_grid(params->w, params->h, params->ncols, tiles, rs);
    else
	gen_grid_random(params->w, params->h, params->ncols, tiles, rs);

    ret = NULL;
    retlen = 0;
    for (i = 0; i < n; i++) {
	char buf[80];
	int k;

	k = sprintf(buf, "%d,", tiles[i]);
	ret = sresize(ret, retlen + k + 1, char);
	strcpy(ret + retlen, buf);
	retlen += k;
    }
    ret[retlen-1] = '\0'; /* delete last comma */

    sfree(tiles);
    return ret;
}

static char *validate_desc(game_params *params, char *desc)
{
    int area = params->w * params->h, i;
    char *p = desc;

    for (i = 0; i < area; i++) {
	char *q = p;
	int n;

	if (!isdigit((unsigned char)*p))
	    return "Not enough numbers in string";
	while (isdigit((unsigned char)*p)) p++;

	if (i < area-1 && *p != ',')
	    return "Expected comma after number";
	else if (i == area-1 && *p)
	    return "Excess junk at end of string";

	n = atoi(q);
	if (n < 0 || n > params->ncols)
	    return "Colour out of range";

	if (*p) p++; /* eat comma */
    }
    return NULL;
}

static game_state *new_game(midend *me, game_params *params, char *desc)
{
    game_state *state = snew(game_state);
    char *p = desc;
    int i;

    state->params = *params; /* struct copy */
    state->n = state->params.w * state->params.h;
    state->tiles = snewn(state->n, int);

    for (i = 0; i < state->n; i++) {
	assert(*p);
	state->tiles[i] = atoi(p);
	while (*p && *p != ',')
            p++;
        if (*p) p++;                   /* eat comma */
    }
    state->complete = state->impossible = 0;
    state->score = 0;

    return state;
}

static game_state *dup_game(game_state *state)
{
    game_state *ret = snew(game_state);

    *ret = *state; /* structure copy, except... */

    ret->tiles = snewn(state->n, int);
    memcpy(ret->tiles, state->tiles, state->n * sizeof(int));

    return ret;
}

static void free_game(game_state *state)
{
    sfree(state->tiles);
    sfree(state);
}

static char *solve_game(game_state *state, game_state *currstate,
			char *aux, char **error)
{
    return NULL;
}

static char *game_text_format(game_state *state)
{
    char *ret, *p;
    int x, y, maxlen;

    maxlen = state->params.h * (state->params.w + 1);
    ret = snewn(maxlen+1, char);
    p = ret;

    for (y = 0; y < state->params.h; y++) {
	for (x = 0; x < state->params.w; x++) {
	    int t = TILE(state,x,y);
	    if (t <= 0)      *p++ = ' ';
	    else if (t < 10) *p++ = '0'+t;
	    else             *p++ = 'a'+(t-10);
	}
	*p++ = '\n';
    }
    assert(p - ret == maxlen);
    *p = '\0';
    return ret;
}

struct game_ui {
    struct game_params params;
    int *tiles; /* selected-ness only */
    int nselected;
    int xsel, ysel, displaysel;
};

static game_ui *new_ui(game_state *state)
{
    game_ui *ui = snew(game_ui);

    ui->params = state->params; /* structure copy */
    ui->tiles = snewn(state->n, int);
    memset(ui->tiles, 0, state->n*sizeof(int));
    ui->nselected = 0;

    ui->xsel = ui->ysel = ui->displaysel = 0;

    return ui;
}

static void free_ui(game_ui *ui)
{
    sfree(ui->tiles);
    sfree(ui);
}

static char *encode_ui(game_ui *ui)
{
    return NULL;
}

static void decode_ui(game_ui *ui, char *encoding)
{
}

static void sel_clear(game_ui *ui, game_state *state)
{
    int i;

    for (i = 0; i < state->n; i++)
	ui->tiles[i] &= ~TILE_SELECTED;
    ui->nselected = 0;
}


static void game_changed_state(game_ui *ui, game_state *oldstate,
                               game_state *newstate)
{
    sel_clear(ui, newstate);

    /*
     * If the game state has just changed into an unplayable one
     * (either completed or impossible), we vanish the keyboard-
     * control cursor.
     */
    if (newstate->complete || newstate->impossible)
	ui->displaysel = 0;
}

static char *sel_movedesc(game_ui *ui, game_state *state)
{
    int i;
    char *ret, *sep, buf[80];
    int retlen, retsize;

    retsize = 256;
    ret = snewn(retsize, char);
    retlen = 0;
    ret[retlen++] = 'M';
    sep = "";

    for (i = 0; i < state->n; i++) {
	if (ui->tiles[i] & TILE_SELECTED) {
	    sprintf(buf, "%s%d", sep, i);
	    sep = ",";
	    if (retlen + strlen(buf) >= retsize) {
		retsize = retlen + strlen(buf) + 256;
		ret = sresize(ret, retsize, char);
	    }
	    strcpy(ret + retlen, buf);
	    retlen += strlen(buf);

	    ui->tiles[i] &= ~TILE_SELECTED;
	}
    }
    ui->nselected = 0;

    assert(retlen < retsize);
    ret[retlen++] = '\0';
    return sresize(ret, retlen, char);
}

static void sel_expand(game_ui *ui, game_state *state, int tx, int ty)
{
    int ns = 1, nadded, x, y, c;

    TILE(ui,tx,ty) |= TILE_SELECTED;
    do {
	nadded = 0;

	for (x = 0; x < state->params.w; x++) {
	    for (y = 0; y < state->params.h; y++) {
		if (x == tx && y == ty) continue;
		if (ISSEL(ui,x,y)) continue;

		c = COL(state,x,y);
		if ((x > 0) &&
		    ISSEL(ui,x-1,y) && COL(state,x-1,y) == c) {
		    TILE(ui,x,y) |= TILE_SELECTED;
		    nadded++;
		    continue;
		}

		if ((x+1 < state->params.w) &&
		    ISSEL(ui,x+1,y) && COL(state,x+1,y) == c) {
		    TILE(ui,x,y) |= TILE_SELECTED;
		    nadded++;
		    continue;
		}

		if ((y > 0) &&
		    ISSEL(ui,x,y-1) && COL(state,x,y-1) == c) {
		    TILE(ui,x,y) |= TILE_SELECTED;
		    nadded++;
		    continue;
		}

		if ((y+1 < state->params.h) &&
		    ISSEL(ui,x,y+1) && COL(state,x,y+1) == c) {
		    TILE(ui,x,y) |= TILE_SELECTED;
		    nadded++;
		    continue;
		}
	    }
	}
	ns += nadded;
    } while (nadded > 0);

    if (ns > 1) {
	ui->nselected = ns;
    } else {
	sel_clear(ui, state);
    }
}

static int sg_emptycol(game_state *ret, int x)
{
    int y;
    for (y = 0; y < ret->params.h; y++) {
	if (COL(ret,x,y)) return 0;
    }
    return 1;
}


static void sg_snuggle(game_state *ret)
{
    int x,y, ndone;

    /* make all unsupported tiles fall down. */
    do {
	ndone = 0;
	for (x = 0; x < ret->params.w; x++) {
	    for (y = ret->params.h-1; y > 0; y--) {
		if (COL(ret,x,y) != 0) continue;
		if (COL(ret,x,y-1) != 0) {
		    SWAPTILE(ret,x,y,x,y-1);
		    ndone++;
		}
	    }
	}
    } while (ndone);

    /* shuffle all columns as far left as they can go. */
    do {
	ndone = 0;
	for (x = 0; x < ret->params.w-1; x++) {
	    if (sg_emptycol(ret,x) && !sg_emptycol(ret,x+1)) {
		ndone++;
		for (y = 0; y < ret->params.h; y++) {
		    SWAPTILE(ret,x,y,x+1,y);
		}
	    }
	}
    } while (ndone);
}

static void sg_check(game_state *ret)
{
    int x,y, complete = 1, impossible = 1;

    for (x = 0; x < ret->params.w; x++) {
	for (y = 0; y < ret->params.h; y++) {
	    if (COL(ret,x,y) == 0)
		continue;
	    complete = 0;
	    if (x+1 < ret->params.w) {
		if (COL(ret,x,y) == COL(ret,x+1,y))
		    impossible = 0;
	    }
	    if (y+1 < ret->params.h) {
		if (COL(ret,x,y) == COL(ret,x,y+1))
		    impossible = 0;
	    }
	}
    }
    ret->complete = complete;
    ret->impossible = impossible;
}

struct game_drawstate {
    int started, bgcolour;
    int tileinner, tilegap;
    int *tiles; /* contains colour and SELECTED. */
};

static char *interpret_move(game_state *state, game_ui *ui, game_drawstate *ds,
			    int x, int y, int button)
{
    int tx, ty;
    char *ret = "";

    ui->displaysel = 0;

    if (button == RIGHT_BUTTON || button == LEFT_BUTTON) {
	tx = FROMCOORD(x); ty= FROMCOORD(y);
    } else if (button == CURSOR_UP || button == CURSOR_DOWN ||
	       button == CURSOR_LEFT || button == CURSOR_RIGHT) {
	int dx = 0, dy = 0;
	ui->displaysel = 1;
	dx = (button == CURSOR_LEFT) ? -1 : ((button == CURSOR_RIGHT) ? +1 : 0);
	dy = (button == CURSOR_DOWN) ? +1 : ((button == CURSOR_UP)    ? -1 : 0);
	ui->xsel = (ui->xsel + state->params.w + dx) % state->params.w;
	ui->ysel = (ui->ysel + state->params.h + dy) % state->params.h;
	return ret;
    } else if (button == CURSOR_SELECT || button == ' ' || button == '\r' ||
	       button == '\n') {
	ui->displaysel = 1;
	tx = ui->xsel;
	ty = ui->ysel;
    } else
	return NULL;

    if (tx < 0 || tx >= state->params.w || ty < 0 || ty >= state->params.h)
	return NULL;
    if (COL(state, tx, ty) == 0) return NULL;

    if (ISSEL(ui,tx,ty)) {
	if (button == RIGHT_BUTTON)
	    sel_clear(ui, state);
	else
	    ret = sel_movedesc(ui, state);
    } else {
	sel_clear(ui, state); /* might be no-op */
	sel_expand(ui, state, tx, ty);
    }

    return ret;
}

static game_state *execute_move(game_state *from, char *move)
{
    int i, n;
    game_state *ret;

    if (move[0] == 'M') {
	ret = dup_game(from);

	n = 0;
	move++;

	while (*move) {
	    i = atoi(move);
	    if (i < 0 || i >= ret->n) {
		free_game(ret);
		return NULL;
	    }
	    n++;
	    ret->tiles[i] = 0;

	    while (*move && isdigit((unsigned char)*move)) move++;
	    if (*move == ',') move++;
	}

	ret->score += npoints(&ret->params, n);

	sg_snuggle(ret); /* shifts blanks down and to the left */
	sg_check(ret);   /* checks for completeness or impossibility */

	return ret;
    } else
	return NULL;		       /* couldn't parse move string */
}

/* ----------------------------------------------------------------------
 * Drawing routines.
 */

static void game_set_size(drawing *dr, game_drawstate *ds,
			  game_params *params, int tilesize)
{
    ds->tilegap = 2;
    ds->tileinner = tilesize - ds->tilegap;
}

static void game_compute_size(game_params *params, int tilesize,
			      int *x, int *y)
{
    /* Ick: fake up tile size variables for macro expansion purposes */
    game_drawstate ads, *ds = &ads;
    game_set_size(NULL, ds, params, tilesize);

    *x = TILE_SIZE * params->w + 2 * BORDER - TILE_GAP;
    *y = TILE_SIZE * params->h + 2 * BORDER - TILE_GAP;
}

static float *game_colours(frontend *fe, int *ncolours)
{
    float *ret = snewn(3 * NCOLOURS, float);

    frontend_default_colour(fe, &ret[COL_BACKGROUND * 3]);

    ret[COL_1 * 3 + 0] = 0.0F;
    ret[COL_1 * 3 + 1] = 0.0F;
    ret[COL_1 * 3 + 2] = 1.0F;

    ret[COL_2 * 3 + 0] = 0.0F;
    ret[COL_2 * 3 + 1] = 0.5F;
    ret[COL_2 * 3 + 2] = 0.0F;

    ret[COL_3 * 3 + 0] = 1.0F;
    ret[COL_3 * 3 + 1] = 0.0F;
    ret[COL_3 * 3 + 2] = 0.0F;

    ret[COL_4 * 3 + 0] = 1.0F;
    ret[COL_4 * 3 + 1] = 1.0F;
    ret[COL_4 * 3 + 2] = 0.0F;

    ret[COL_5 * 3 + 0] = 1.0F;
    ret[COL_5 * 3 + 1] = 0.0F;
    ret[COL_5 * 3 + 2] = 1.0F;

    ret[COL_6 * 3 + 0] = 0.0F;
    ret[COL_6 * 3 + 1] = 1.0F;
    ret[COL_6 * 3 + 2] = 1.0F;

    ret[COL_7 * 3 + 0] = 0.5F;
    ret[COL_7 * 3 + 1] = 0.5F;
    ret[COL_7 * 3 + 2] = 1.0F;

    ret[COL_8 * 3 + 0] = 0.5F;
    ret[COL_8 * 3 + 1] = 1.0F;
    ret[COL_8 * 3 + 2] = 0.5F;

    ret[COL_9 * 3 + 0] = 1.0F;
    ret[COL_9 * 3 + 1] = 0.5F;
    ret[COL_9 * 3 + 2] = 0.5F;

    ret[COL_IMPOSSIBLE * 3 + 0] = 0.0F;
    ret[COL_IMPOSSIBLE * 3 + 1] = 0.0F;
    ret[COL_IMPOSSIBLE * 3 + 2] = 0.0F;

    ret[COL_SEL * 3 + 0] = 1.0F;
    ret[COL_SEL * 3 + 1] = 1.0F;
    ret[COL_SEL * 3 + 2] = 1.0F;

    ret[COL_HIGHLIGHT * 3 + 0] = 1.0F;
    ret[COL_HIGHLIGHT * 3 + 1] = 1.0F;
    ret[COL_HIGHLIGHT * 3 + 2] = 1.0F;

    ret[COL_LOWLIGHT * 3 + 0] = ret[COL_BACKGROUND * 3 + 0] * 2.0 / 3.0;
    ret[COL_LOWLIGHT * 3 + 1] = ret[COL_BACKGROUND * 3 + 1] * 2.0 / 3.0;
    ret[COL_LOWLIGHT * 3 + 2] = ret[COL_BACKGROUND * 3 + 2] * 2.0 / 3.0;

    *ncolours = NCOLOURS;
    return ret;
}

static game_drawstate *game_new_drawstate(drawing *dr, game_state *state)
{
    struct game_drawstate *ds = snew(struct game_drawstate);
    int i;

    ds->started = 0;
    ds->tileinner = ds->tilegap = 0;   /* not decided yet */
    ds->tiles = snewn(state->n, int);
    ds->bgcolour = -1;
    for (i = 0; i < state->n; i++)
	ds->tiles[i] = -1;

    return ds;
}

static void game_free_drawstate(drawing *dr, game_drawstate *ds)
{
    sfree(ds->tiles);
    sfree(ds);
}

/* Drawing routing for the tile at (x,y) is responsible for drawing
 * itself and the gaps to its right and below. If we're the same colour
 * as the tile to our right, then we fill in the gap; ditto below, and if
 * both then we fill the teeny tiny square in the corner as well.
 */

static void tile_redraw(drawing *dr, game_drawstate *ds,
			int x, int y, int dright, int dbelow,
                        int tile, int bgcolour)
{
    int outer = bgcolour, inner = outer, col = tile & TILE_COLMASK;

    if (col) {
	if (tile & TILE_IMPOSSIBLE) {
	    outer = col;
	    inner = COL_IMPOSSIBLE;
	} else if (tile & TILE_SELECTED) {
	    outer = COL_SEL;
	    inner = col;
	} else {
	    outer = inner = col;
	}
    }
    draw_rect(dr, COORD(x), COORD(y), TILE_INNER, TILE_INNER, outer);
    draw_rect(dr, COORD(x)+TILE_INNER/4, COORD(y)+TILE_INNER/4,
	      TILE_INNER/2, TILE_INNER/2, inner);

    if (dright)
	draw_rect(dr, COORD(x)+TILE_INNER, COORD(y), TILE_GAP, TILE_INNER,
		  (tile & TILE_JOINRIGHT) ? outer : bgcolour);
    if (dbelow)
	draw_rect(dr, COORD(x), COORD(y)+TILE_INNER, TILE_INNER, TILE_GAP,
		  (tile & TILE_JOINDOWN) ? outer : bgcolour);
    if (dright && dbelow)
	draw_rect(dr, COORD(x)+TILE_INNER, COORD(y)+TILE_INNER, TILE_GAP, TILE_GAP,
		  (tile & TILE_JOINDIAG) ? outer : bgcolour);

    if (tile & TILE_HASSEL) {
	int sx = COORD(x)+2, sy = COORD(y)+2, ssz = TILE_INNER-5;
	int scol = (outer == COL_SEL) ? COL_LOWLIGHT : COL_HIGHLIGHT;
	draw_line(dr, sx,     sy,     sx+ssz, sy,     scol);
	draw_line(dr, sx+ssz, sy,     sx+ssz, sy+ssz, scol);
	draw_line(dr, sx+ssz, sy+ssz, sx,     sy+ssz, scol);
	draw_line(dr, sx,     sy+ssz, sx,     sy,     scol);
    }

    draw_update(dr, COORD(x), COORD(y), TILE_SIZE, TILE_SIZE);
}

static void game_redraw(drawing *dr, game_drawstate *ds, game_state *oldstate,
			game_state *state, int dir, game_ui *ui,
			float animtime, float flashtime)
{
    int bgcolour, x, y;

    /* This was entirely cloned from fifteen.c; it should probably be
     * moved into some generic 'draw-recessed-rectangle' utility fn. */
    if (!ds->started) {
	int coords[10];

	draw_rect(dr, 0, 0,
		  TILE_SIZE * state->params.w + 2 * BORDER,
		  TILE_SIZE * state->params.h + 2 * BORDER, COL_BACKGROUND);
	draw_update(dr, 0, 0,
		    TILE_SIZE * state->params.w + 2 * BORDER,
		    TILE_SIZE * state->params.h + 2 * BORDER);

	/*
	 * Recessed area containing the whole puzzle.
	 */
	coords[0] = COORD(state->params.w) + HIGHLIGHT_WIDTH - 1 - TILE_GAP;
	coords[1] = COORD(state->params.h) + HIGHLIGHT_WIDTH - 1 - TILE_GAP;
	coords[2] = COORD(state->params.w) + HIGHLIGHT_WIDTH - 1 - TILE_GAP;
	coords[3] = COORD(0) - HIGHLIGHT_WIDTH;
	coords[4] = coords[2] - TILE_SIZE;
	coords[5] = coords[3] + TILE_SIZE;
	coords[8] = COORD(0) - HIGHLIGHT_WIDTH;
	coords[9] = COORD(state->params.h) + HIGHLIGHT_WIDTH - 1 - TILE_GAP;
	coords[6] = coords[8] + TILE_SIZE;
	coords[7] = coords[9] - TILE_SIZE;
	draw_polygon(dr, coords, 5, COL_HIGHLIGHT, COL_HIGHLIGHT);

	coords[1] = COORD(0) - HIGHLIGHT_WIDTH;
	coords[0] = COORD(0) - HIGHLIGHT_WIDTH;
	draw_polygon(dr, coords, 5, COL_LOWLIGHT, COL_LOWLIGHT);

	ds->started = 1;
    }

    if (flashtime > 0.0) {
	int frame = (int)(flashtime / FLASH_FRAME);
	bgcolour = (frame % 2 ? COL_LOWLIGHT : COL_HIGHLIGHT);
    } else
	bgcolour = COL_BACKGROUND;

    for (x = 0; x < state->params.w; x++) {
	for (y = 0; y < state->params.h; y++) {
	    int i = (state->params.w * y) + x;
	    int col = COL(state,x,y), tile = col;
	    int dright = (x+1 < state->params.w);
	    int dbelow = (y+1 < state->params.h);

	    tile |= ISSEL(ui,x,y);
	    if (state->impossible)
		tile |= TILE_IMPOSSIBLE;
	    if (dright && COL(state,x+1,y) == col)
		tile |= TILE_JOINRIGHT;
	    if (dbelow && COL(state,x,y+1) == col)
		tile |= TILE_JOINDOWN;
	    if ((tile & TILE_JOINRIGHT) && (tile & TILE_JOINDOWN) &&
		COL(state,x+1,y+1) == col)
		tile |= TILE_JOINDIAG;

	    if (ui->displaysel && ui->xsel == x && ui->ysel == y)
		tile |= TILE_HASSEL;

	    /* For now we're never expecting oldstate at all (because we have
	     * no animation); when we do we might well want to be looking
	     * at the tile colours from oldstate, not state. */
	    if ((oldstate && COL(oldstate,x,y) != col) ||
		(ds->bgcolour != bgcolour) ||
		(tile != ds->tiles[i])) {
		tile_redraw(dr, ds, x, y, dright, dbelow, tile, bgcolour);
		ds->tiles[i] = tile;
	    }
	}
    }
    ds->bgcolour = bgcolour;

    {
	char status[255], score[80];

	sprintf(score, "Score: %d", state->score);

	if (state->complete)
	    sprintf(status, "COMPLETE! %s", score);
	else if (state->impossible)
	    sprintf(status, "Cannot move! %s", score);
	else if (ui->nselected)
	    sprintf(status, "%s  Selected: %d (%d)",
		    score, ui->nselected, npoints(&state->params, ui->nselected));
	else
	    sprintf(status, "%s", score);
	status_bar(dr, status);
    }
}

static float game_anim_length(game_state *oldstate, game_state *newstate,
			      int dir, game_ui *ui)
{
    return 0.0F;
}

static float game_flash_length(game_state *oldstate, game_state *newstate,
			       int dir, game_ui *ui)
{
    if ((!oldstate->complete && newstate->complete) ||
        (!oldstate->impossible && newstate->impossible))
	return 2 * FLASH_FRAME;
    else
	return 0.0F;
}

static int game_timing_state(game_state *state, game_ui *ui)
{
    return TRUE;
}

static void game_print_size(game_params *params, float *x, float *y)
{
}

static void game_print(drawing *dr, game_state *state, int tilesize)
{
}

#ifdef COMBINED
#define thegame samegame
#endif

const struct game thegame = {
    "Same Game", "samegame",
    default_params,
    game_fetch_preset,
    decode_params,
    encode_params,
    free_params,
    dup_params,
    TRUE, game_configure, custom_params,
    validate_params,
    new_game_desc,
    validate_desc,
    new_game,
    dup_game,
    free_game,
    FALSE, solve_game,
    TRUE, game_text_format,
    new_ui,
    free_ui,
    encode_ui,
    decode_ui,
    game_changed_state,
    interpret_move,
    execute_move,
    PREFERRED_TILE_SIZE, game_compute_size, game_set_size,
    game_colours,
    game_new_drawstate,
    game_free_drawstate,
    game_redraw,
    game_anim_length,
    game_flash_length,
    FALSE, FALSE, game_print_size, game_print,
    TRUE,			       /* wants_statusbar */
    FALSE, game_timing_state,
    0,				       /* flags */
};