Added a new game, `Rectangles', taken from nikoli.co.jp.
authorsimon <simon@cda61777-01e9-0310-a592-d414129be87e>
Tue, 11 May 2004 17:06:50 +0000 (17:06 +0000)
committersimon <simon@cda61777-01e9-0310-a592-d414129be87e>
Tue, 11 May 2004 17:06:50 +0000 (17:06 +0000)
git-svn-id: svn://svn.tartarus.org/sgt/puzzles@4206 cda61777-01e9-0310-a592-d414129be87e

.cvsignore
Recipe
rect.c [new file with mode: 0644]

index faa8661..a869da5 100644 (file)
@@ -1,5 +1,5 @@
 Makefile*
-net cube fifteen sixteen nullgame
+net cube fifteen sixteen rect nullgame
 *.exe *.obj *.o
 *.map *.rsp
 *notes
diff --git a/Recipe b/Recipe
index 9d7c1e9..76e6cb1 100644 (file)
--- a/Recipe
+++ b/Recipe
@@ -20,11 +20,13 @@ net      : [X] gtk COMMON NET
 cube     : [X] gtk COMMON cube
 fifteen  : [X] gtk COMMON fifteen
 sixteen  : [X] gtk COMMON sixteen
+rect     : [X] gtk COMMON rect
 
 net      : [G] WINDOWS COMMON NET
 cube     : [G] WINDOWS COMMON cube
 fifteen  : [G] WINDOWS COMMON fifteen
 sixteen  : [G] WINDOWS COMMON sixteen
+rect     : [G] WINDOWS COMMON rect
 
 # The `nullgame' source file is a largely blank one, which contains
 # all the correct function definitions to compile and link, but
diff --git a/rect.c b/rect.c
new file mode 100644 (file)
index 0000000..87e86bf
--- /dev/null
+++ b/rect.c
@@ -0,0 +1,1058 @@
+/*
+ * rect.c: Puzzle from nikoli.co.jp. You have a square grid with
+ * numbers in some squares; you must divide the square grid up into
+ * variously sized rectangles, such that every rectangle contains
+ * exactly one numbered square and the area of each rectangle is
+ * equal to the number contained in it.
+ */
+
+/*
+ * TODO:
+ * 
+ *  - Improve on singleton removal by making an aesthetic choice
+ *    about which of the options to take.
+ * 
+ *  - When doing the 3x3 trick in singleton removal, limit the size
+ *    of the generated rectangles in accordance with the max
+ *    rectangle size.
+ * 
+ *  - It might be interesting to deliberately try to place
+ *    numbers so as to reduce alternative solution patterns. I
+ *    doubt we can do a perfect job of this, but we can make a
+ *    start by, for example, noticing pairs of 2-rects
+ *    alongside one another and _not_ putting their numbers at
+ *    opposite ends.
+ *
+ *  - If we start by sorting the rectlist in descending order
+ *    of area, we might be able to bias our random number
+ *    selection to produce a few large rectangles more often
+ *    than oodles of small ones? Unsure, but might be worth a
+ *    try.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include <math.h>
+
+#include "puzzles.h"
+
+const char *const game_name = "Rectangles";
+const int game_can_configure = TRUE;
+
+enum {
+    COL_BACKGROUND,
+    COL_CORRECT,
+    COL_LINE,
+    COL_TEXT,
+    COL_GRID,
+    NCOLOURS
+};
+
+struct game_params {
+    int w, h;
+};
+
+#define INDEX(state, x, y)    (((y) * (state)->w) + (x))
+#define index(state, a, x, y) ((a) [ INDEX(state,x,y) ])
+#define grid(state,x,y)       index(state, (state)->grid, x, y)
+#define vedge(state,x,y)      index(state, (state)->vedge, x, y)
+#define hedge(state,x,y)      index(state, (state)->hedge, x, y)
+
+#define CRANGE(state,x,y,dx,dy) ( (x) >= dx && (x) < (state)->w && \
+                               (y) >= dy && (y) < (state)->h )
+#define RANGE(state,x,y)  CRANGE(state,x,y,0,0)
+#define HRANGE(state,x,y) CRANGE(state,x,y,0,1)
+#define VRANGE(state,x,y) CRANGE(state,x,y,1,0)
+
+#define TILE_SIZE 24
+#define BORDER 18
+
+#define COORD(x) ( (x) * TILE_SIZE + BORDER )
+#define FROMCOORD(x) ( ((x) - BORDER) / TILE_SIZE )
+
+struct game_state {
+    int w, h;
+    int *grid;                        /* contains the numbers */
+    unsigned char *vedge;             /* (w+1) x h */
+    unsigned char *hedge;             /* w x (h+1) */
+};
+
+game_params *default_params(void)
+{
+    game_params *ret = snew(game_params);
+
+    ret->w = ret->h = 7;
+
+    return ret;
+}
+
+int game_fetch_preset(int i, char **name, game_params **params)
+{
+    game_params *ret;
+    int w, h;
+    char buf[80];
+
+    switch (i) {
+      case 0: w = 7, h = 7; break;
+      case 1: w = 11, h = 11; break;
+      case 2: w = 15, h = 15; break;
+      case 3: w = 19, h = 19; break;
+      default: return FALSE;
+    }
+
+    sprintf(buf, "%dx%d", w, h);
+    *name = dupstr(buf);
+    *params = ret = snew(game_params);
+    ret->w = w;
+    ret->h = h;
+    return TRUE;
+}
+
+void free_params(game_params *params)
+{
+    sfree(params);
+}
+
+game_params *dup_params(game_params *params)
+{
+    game_params *ret = snew(game_params);
+    *ret = *params;                   /* structure copy */
+    return ret;
+}
+
+config_item *game_configure(game_params *params)
+{
+    config_item *ret;
+    char buf[80];
+
+    ret = snewn(5, 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 = NULL;
+    ret[2].type = C_END;
+    ret[2].sval = NULL;
+    ret[2].ival = 0;
+
+    return ret;
+}
+
+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);
+
+    return ret;
+}
+
+char *validate_params(game_params *params)
+{
+    if (params->w <= 0 && params->h <= 0)
+       return "Width and height must both be greater than zero";
+    if (params->w * params->h < 4)
+       return "Total area must be at least 4";
+    return NULL;
+}
+
+struct rect {
+    int x, y;
+    int w, h;
+};
+
+struct rectlist {
+    struct rect *rects;
+    int n;
+};
+
+static struct rectlist *get_rectlist(game_params *params, int *grid)
+{
+    int rw, rh;
+    int x, y;
+    int maxarea;
+    struct rect *rects = NULL;
+    int nrects = 0, rectsize = 0;
+
+    /*
+     * Maximum rectangle area is 1/6 of total grid size.
+     */
+    maxarea = params->w * params->h / 6;
+
+    for (rw = 1; rw <= params->w; rw++)
+        for (rh = 1; rh <= params->h; rh++) {
+            if (rw * rh > maxarea)
+                continue;
+            if (rw * rh == 1)
+                continue;
+            for (x = 0; x <= params->w - rw; x++)
+                for (y = 0; y <= params->h - rh; y++) {
+                    /*
+                     * We have a candidate rectangle placement. See
+                     * if it's unobstructed.
+                     */
+                    int xx, yy;
+                    int ok;
+
+                    ok = TRUE;
+                    for (xx = x; xx < x+rw; xx++)
+                        for (yy = y; yy < y+rh; yy++)
+                            if (index(params, grid, xx, yy) >= 0) {
+                                ok = FALSE;
+                                goto break1;   /* break both loops at once */
+                            }
+                    break1:
+
+                    if (!ok)
+                        continue;
+
+                    if (nrects >= rectsize) {
+                        rectsize = nrects + 256;
+                        rects = sresize(rects, rectsize, struct rect);
+                    }
+
+                    rects[nrects].x = x;
+                    rects[nrects].y = y;
+                    rects[nrects].w = rw;
+                    rects[nrects].h = rh;
+                    nrects++;
+                }
+        }
+
+    if (nrects > 0) {
+        struct rectlist *ret;
+        ret = snew(struct rectlist);
+        ret->rects = rects;
+        ret->n = nrects;
+        return ret;
+    } else {
+        assert(rects == NULL);         /* hence no need to free */
+        return NULL;
+    }
+}
+
+static void free_rectlist(struct rectlist *list)
+{
+    sfree(list->rects);
+    sfree(list);
+}
+
+static void place_rect(game_params *params, int *grid, struct rect r)
+{
+    int idx = INDEX(params, r.x, r.y);
+    int x, y;
+
+    for (x = r.x; x < r.x+r.w; x++)
+        for (y = r.y; y < r.y+r.h; y++) {
+            index(params, grid, x, y) = idx;
+        }
+#ifdef GENERATION_DIAGNOSTICS
+    printf("    placing rectangle at (%d,%d) size %d x %d\n",
+           r.x, r.y, r.w, r.h);
+#endif
+}
+
+static struct rect find_rect(game_params *params, int *grid, int x, int y)
+{
+    int idx, w, h;
+    struct rect r;
+
+    /*
+     * Find the top left of the rectangle.
+     */
+    idx = index(params, grid, x, y);
+
+    if (idx < 0) {
+        r.x = x;
+        r.y = y;
+        r.w = r.h = 1;
+        return r;                      /* 1x1 singleton here */
+    }
+
+    y = idx / params->w;
+    x = idx % params->w;
+
+    /*
+     * Find the width and height of the rectangle.
+     */
+    for (w = 1;
+         (x+w < params->w && index(params,grid,x+w,y)==idx);
+         w++);
+    for (h = 1;
+         (y+h < params->h && index(params,grid,x,y+h)==idx);
+         h++);
+
+    r.x = x;
+    r.y = y;
+    r.w = w;
+    r.h = h;
+
+    return r;
+}
+
+#ifdef GENERATION_DIAGNOSTICS
+static void display_grid(game_params *params, int *grid, int *numbers)
+{
+    unsigned char *egrid = snewn((params->w*2+3) * (params->h*2+3),
+                                 unsigned char);
+    memset(egrid, 0, (params->w*2+3) * (params->h*2+3));
+    int x, y;
+    int r = (params->w*2+3);
+
+    for (x = 0; x < params->w; x++)
+        for (y = 0; y < params->h; y++) {
+            int i = index(params, grid, x, y);
+            if (x == 0 || index(params, grid, x-1, y) != i)
+                egrid[(2*y+2) * r + (2*x+1)] = 1;
+            if (x == params->w-1 || index(params, grid, x+1, y) != i)
+                egrid[(2*y+2) * r + (2*x+3)] = 1;
+            if (y == 0 || index(params, grid, x, y-1) != i)
+                egrid[(2*y+1) * r + (2*x+2)] = 1;
+            if (y == params->h-1 || index(params, grid, x, y+1) != i)
+                egrid[(2*y+3) * r + (2*x+2)] = 1;
+        }
+
+    for (y = 1; y < 2*params->h+2; y++) {
+        for (x = 1; x < 2*params->w+2; x++) {
+            if (!((y|x)&1)) {
+                int k = index(params, numbers, x/2-1, y/2-1);
+                if (k) printf("%2d", k); else printf("  ");
+            } else if (!((y&x)&1)) {
+                int v = egrid[y*r+x];
+                if ((y&1) && v) v = '-';
+                if ((x&1) && v) v = '|';
+                if (!v) v = ' ';
+                putchar(v);
+                if (!(x&1)) putchar(v);
+            } else {
+                int c, d = 0;
+                if (egrid[y*r+(x+1)]) d |= 1;
+                if (egrid[(y-1)*r+x]) d |= 2;
+                if (egrid[y*r+(x-1)]) d |= 4;
+                if (egrid[(y+1)*r+x]) d |= 8;
+                c = " ??+?-++?+|+++++"[d];
+                putchar(c);
+                if (!(x&1)) putchar(c);
+            }
+        }
+        putchar('\n');
+    }
+
+    sfree(egrid);
+}
+#endif
+
+char *new_game_seed(game_params *params, random_state *rs)
+{
+    int *grid, *numbers;
+    struct rectlist *list;
+    int x, y, run, i;
+    char *seed, *p;
+
+    grid = snewn(params->w * params->h, int);
+    numbers = snewn(params->w * params->h, int);
+
+    for (y = 0; y < params->h; y++)
+        for (x = 0; x < params->w; x++) {
+            index(params, grid, x, y) = -1;
+            index(params, numbers, x, y) = 0;
+        }
+
+    list = get_rectlist(params, grid);
+    assert(list != NULL);
+
+    /*
+     * Place rectangles until we can't any more.
+     */
+    while (list->n > 0) {
+        int i, m;
+        struct rect r;
+
+        /*
+         * Pick a random rectangle.
+         */
+        i = random_upto(rs, list->n);
+        r = list->rects[i];
+
+        /*
+         * Place it.
+         */
+        place_rect(params, grid, r);
+
+        /*
+         * Winnow the list by removing any rectangles which
+         * overlap this one.
+         */
+        m = 0;
+        for (i = 0; i < list->n; i++) {
+            struct rect s = list->rects[i];
+            if (s.x+s.w <= r.x || r.x+r.w <= s.x ||
+                s.y+s.h <= r.y || r.y+r.h <= s.y)
+                list->rects[m++] = s;
+        }
+        list->n = m;
+    }
+
+    free_rectlist(list);
+
+    /*
+     * Deal with singleton spaces remaining in the grid, one by
+     * one.
+     * 
+     * We do this by making a local change to the layout. There are
+     * several possibilities:
+     * 
+     *     +-----+-----+    Here, we can remove the singleton by
+     *     |     |     |    extending the 1x2 rectangle below it
+     *     +--+--+-----+    into a 1x3.
+     *     |  |  |     |
+     *     |  +--+     |
+     *     |  |  |     |
+     *     |  |  |     |
+     *     |  |  |     |
+     *     +--+--+-----+
+     * 
+     *     +--+--+--+       Here, that trick doesn't work: there's no
+     *     |     |  |       1 x n rectangle with the singleton at one
+     *     |     |  |       end. Instead, we extend a 1 x n rectangle
+     *     |     |  |       _out_ from the singleton, shaving a layer
+     *     +--+--+  |       off the end of another rectangle. So if we
+     *     |  |  |  |       extended up, we'd make our singleton part
+     *     |  +--+--+       of a 1x3 and generate a 1x2 where the 2x2
+     *     |  |     |       used to be; or we could extend right into
+     *     +--+-----+       a 2x1, turning the 1x3 into a 1x2.
+     * 
+     *     +-----+--+       Here, we can't even do _that_, since any
+     *     |     |  |       direction we choose to extend the singleton
+     *     +--+--+  |       will produce a new singleton as a result of
+     *     |  |  |  |       truncating one of the size-2 rectangles.
+     *     |  +--+--+       Fortunately, this case can _only_ occur when
+     *     |  |     |       a singleton is surrounded by four size-2s
+     *     +--+-----+       in this fashion; so instead we can simply
+     *                      replace the whole section with a single 3x3.
+     */
+    for (x = 0; x < params->w; x++) {
+        for (y = 0; y < params->h; y++) {
+            if (index(params, grid, x, y) < 0) {
+                int dirs[4], ndirs;
+
+#ifdef GENERATION_DIAGNOSTICS
+                display_grid(params, grid, numbers);
+                printf("singleton at %d,%d\n", x, y);
+#endif
+
+                /*
+                 * Check in which directions we can feasibly extend
+                 * the singleton. We can extend in a particular
+                 * direction iff either:
+                 * 
+                 *  - the rectangle on that side of the singleton
+                 *    is not 2x1, and we are at one end of the edge
+                 *    of it we are touching
+                 * 
+                 *  - it is 2x1 but we are on its short side.
+                 * 
+                 * FIXME: we could plausibly choose between these
+                 * based on the sizes of the rectangles they would
+                 * create?
+                 */
+                ndirs = 0;
+                if (x < params->w-1) {
+                    struct rect r = find_rect(params, grid, x+1, y);
+                    if ((r.w * r.h > 2 && (r.y==y || r.y+r.h-1==y)) || r.h==1)
+                        dirs[ndirs++] = 1;   /* right */
+                }
+                if (y > 0) {
+                    struct rect r = find_rect(params, grid, x, y-1);
+                    if ((r.w * r.h > 2 && (r.x==x || r.x+r.w-1==x)) || r.w==1)
+                        dirs[ndirs++] = 2;   /* up */
+                }
+                if (x > 0) {
+                    struct rect r = find_rect(params, grid, x-1, y);
+                    if ((r.w * r.h > 2 && (r.y==y || r.y+r.h-1==y)) || r.h==1)
+                        dirs[ndirs++] = 4;   /* left */
+                }
+                if (y < params->h-1) {
+                    struct rect r = find_rect(params, grid, x, y+1);
+                    if ((r.w * r.h > 2 && (r.x==x || r.x+r.w-1==x)) || r.w==1)
+                        dirs[ndirs++] = 8;   /* down */
+                }
+
+                if (ndirs > 0) {
+                    int which, dir;
+                    struct rect r1, r2;
+
+                    which = random_upto(rs, ndirs);
+                    dir = dirs[which];
+
+                    switch (dir) {
+                      case 1:          /* right */
+                        assert(x < params->w+1);
+#ifdef GENERATION_DIAGNOSTICS
+                        printf("extending right\n");
+#endif
+                        r1 = find_rect(params, grid, x+1, y);
+                        r2.x = x;
+                        r2.y = y;
+                        r2.w = 1 + r1.w;
+                        r2.h = 1;
+                        if (r1.y == y)
+                            r1.y++;
+                        r1.h--;
+                        break;
+                      case 2:          /* up */
+                        assert(y > 0);
+#ifdef GENERATION_DIAGNOSTICS
+                        printf("extending up\n");
+#endif
+                        r1 = find_rect(params, grid, x, y-1);
+                        r2.x = x;
+                        r2.y = r1.y;
+                        r2.w = 1;
+                        r2.h = 1 + r1.h;
+                        if (r1.x == x)
+                            r1.x++;
+                        r1.w--;
+                        break;
+                      case 4:          /* left */
+                        assert(x > 0);
+#ifdef GENERATION_DIAGNOSTICS
+                        printf("extending left\n");
+#endif
+                        r1 = find_rect(params, grid, x-1, y);
+                        r2.x = r1.x;
+                        r2.y = y;
+                        r2.w = 1 + r1.w;
+                        r2.h = 1;
+                        if (r1.y == y)
+                            r1.y++;
+                        r1.h--;
+                        break;
+                      case 8:          /* down */
+                        assert(y < params->h+1);
+#ifdef GENERATION_DIAGNOSTICS
+                        printf("extending down\n");
+#endif
+                        r1 = find_rect(params, grid, x, y+1);
+                        r2.x = x;
+                        r2.y = y;
+                        r2.w = 1;
+                        r2.h = 1 + r1.h;
+                        if (r1.x == x)
+                            r1.x++;
+                        r1.w--;
+                        break;
+                    }
+                    if (r1.h > 0 && r1.w > 0)
+                        place_rect(params, grid, r1);
+                    place_rect(params, grid, r2);
+                } else {
+#ifndef NDEBUG
+                    /*
+                     * Sanity-check that there really is a 3x3
+                     * rectangle surrounding this singleton and it
+                     * contains absolutely everything we could
+                     * possibly need.
+                     */
+                    {
+                        int xx, yy;
+                        assert(x > 0 && x < params->w-1);
+                        assert(y > 0 && y < params->h-1);
+
+                        for (xx = x-1; xx <= x+1; xx++)
+                            for (yy = y-1; yy <= y+1; yy++) {
+                                struct rect r = find_rect(params,grid,xx,yy);
+                                assert(r.x >= x-1);
+                                assert(r.y >= y-1);
+                                assert(r.x+r.w-1 <= x+1);
+                                assert(r.y+r.h-1 <= y+1);
+                            }
+                    }
+#endif
+                    
+#ifdef GENERATION_DIAGNOSTICS
+                    printf("need the 3x3 trick\n");
+#endif
+
+                    /*
+                     * FIXME: If the maximum rectangle area for
+                     * this grid is less than 9, we ought to
+                     * subdivide the 3x3 in some fashion. There are
+                     * five other possibilities:
+                     * 
+                     *  - a 6 and a 3
+                     *  - a 4, a 3 and a 2
+                     *  - three 3s
+                     *  - a 3 and three 2s (two different arrangements).
+                     */
+
+                    {
+                        struct rect r;
+                        r.x = x-1;
+                        r.y = y-1;
+                        r.w = r.h = 3;
+                        place_rect(params, grid, r);
+                    }
+                }
+            }
+        }
+    }
+
+    /*
+     * Place numbers.
+     */
+    for (x = 0; x < params->w; x++) {
+        for (y = 0; y < params->h; y++) {
+            int idx = INDEX(params, x, y);
+            if (index(params, grid, x, y) == idx) {
+                struct rect r = find_rect(params, grid, x, y);
+                int n, xx, yy;
+
+                /*
+                 * Decide where to put the number.
+                 */
+                n = random_upto(rs, r.w*r.h);
+                yy = n / r.w;
+                xx = n % r.w;
+                index(params,numbers,x+xx,y+yy) = r.w*r.h;
+            }
+        }
+    }
+
+#ifdef GENERATION_DIAGNOSTICS
+    display_grid(params, grid, numbers);
+#endif
+
+    seed = snewn(11 * params->w * params->h, char);
+    p = seed;
+    run = 0;
+    for (i = 0; i <= params->w * params->h; i++) {
+        int n = (i < params->w * params->h ? numbers[i] : -1);
+
+        if (!n)
+            run++;
+        else {
+            if (run) {
+                while (run > 0) {
+                    int c = 'a' - 1 + run;
+                    if (run > 26)
+                        c = 'z';
+                    *p++ = c;
+                    run -= c - ('a' - 1);
+                }
+            } else {
+                *p++ = '_';
+            }
+            if (n > 0)
+                p += sprintf(p, "%d", n);
+            run = 0;
+        }
+    }
+    *p = '\0';
+
+    sfree(grid);
+    sfree(numbers);
+
+    return seed;
+}
+
+char *validate_seed(game_params *params, char *seed)
+{
+    int area = params->w * params->h;
+    int squares = 0;
+
+    while (*seed) {
+        int n = *seed++;
+        if (n >= 'a' && n <= 'z') {
+            squares += n - 'a' + 1;
+        } else if (n == '_') {
+            /* do nothing */;
+        } else if (n > '0' && n <= '9') {
+            squares += atoi(seed-1);
+            while (*seed >= '0' && *seed <= '9')
+                seed++;
+        } else
+            return "Invalid character in game specification";
+    }
+
+    if (squares < area)
+        return "Not enough data to fill grid";
+
+    if (squares > area)
+        return "Too much data to fit in grid";
+
+    return NULL;
+}
+
+game_state *new_game(game_params *params, char *seed)
+{
+    game_state *state = snew(game_state);
+    int x, y, i, area;
+
+    state->w = params->w;
+    state->h = params->h;
+
+    area = state->w * state->h;
+
+    state->grid = snewn(area, int);
+    state->vedge = snewn(area, unsigned char);
+    state->hedge = snewn(area, unsigned char);
+
+    i = 0;
+    while (*seed) {
+        int n = *seed++;
+        if (n >= 'a' && n <= 'z') {
+            int run = n - 'a' + 1;
+            assert(i + run <= area);
+            while (run-- > 0)
+                state->grid[i++] = 0;
+        } else if (n == '_') {
+            /* do nothing */;
+        } else if (n > '0' && n <= '9') {
+            assert(i < area);
+            state->grid[i++] = atoi(seed-1);
+            while (*seed >= '0' && *seed <= '9')
+                seed++;
+        } else {
+            assert(!"We can't get here");
+        }
+    }
+    assert(i == area);
+
+    for (y = 0; y < state->h; y++)
+       for (x = 0; x < state->w; x++)
+           vedge(state,x,y) = hedge(state,x,y) = 0;
+
+    return state;
+}
+
+game_state *dup_game(game_state *state)
+{
+    game_state *ret = snew(game_state);
+
+    ret->w = state->w;
+    ret->h = state->h;
+
+    ret->vedge = snewn(state->w * state->h, unsigned char);
+    ret->hedge = snewn(state->w * state->h, unsigned char);
+    ret->grid = snewn(state->w * state->h, int);
+
+    memcpy(ret->grid, state->grid, state->w * state->h * sizeof(int));
+    memcpy(ret->vedge, state->vedge, state->w*state->h*sizeof(unsigned char));
+    memcpy(ret->hedge, state->hedge, state->w*state->h*sizeof(unsigned char));
+
+    return ret;
+}
+
+void free_game(game_state *state)
+{
+    sfree(state->grid);
+    sfree(state->vedge);
+    sfree(state->hedge);
+    sfree(state);
+}
+
+static unsigned char *get_correct(game_state *state)
+{
+    unsigned char *ret;
+    int x, y;
+
+    ret = snewn(state->w * state->h, unsigned char);
+    memset(ret, 0xFF, state->w * state->h);
+
+    for (x = 0; x < state->w; x++)
+       for (y = 0; y < state->h; y++)
+           if (index(state,ret,x,y) == 0xFF) {
+               int rw, rh;
+               int xx, yy;
+               int num, area, valid;
+
+               /*
+                * Find a rectangle starting at this point.
+                */
+               rw = 1;
+               while (x+rw < state->w && !vedge(state,x+rw,y))
+                   rw++;
+               rh = 1;
+               while (y+rh < state->h && !hedge(state,x,y+rh))
+                   rh++;
+
+               /*
+                * We know what the dimensions of the rectangle
+                * should be if it's there at all. Find out if we
+                * really have a valid rectangle.
+                */
+               valid = TRUE;
+               /* Check the horizontal edges. */
+               for (xx = x; xx < x+rw; xx++) {
+                   for (yy = y; yy <= y+rh; yy++) {
+                       int e = !HRANGE(state,xx,yy) || hedge(state,xx,yy);
+                       int ec = (yy == y || yy == y+rh);
+                       if (e != ec)
+                           valid = FALSE;
+                   }
+               }
+               /* Check the vertical edges. */
+               for (yy = y; yy < y+rh; yy++) {
+                   for (xx = x; xx <= x+rw; xx++) {
+                       int e = !VRANGE(state,xx,yy) || vedge(state,xx,yy);
+                       int ec = (xx == x || xx == x+rw);
+                       if (e != ec)
+                           valid = FALSE;
+                   }
+               }
+
+               /*
+                * If this is not a valid rectangle with no other
+                * edges inside it, we just mark this square as not
+                * complete and proceed to the next square.
+                */
+               if (!valid) {
+                   index(state, ret, x, y) = 0;
+                   continue;
+               }
+
+               /*
+                * We have a rectangle. Now see what its area is,
+                * and how many numbers are in it.
+                */
+               num = 0;
+               area = 0;
+               for (xx = x; xx < x+rw; xx++) {
+                   for (yy = y; yy < y+rh; yy++) {
+                       area++;
+                       if (grid(state,xx,yy)) {
+                           if (num > 0)
+                               valid = FALSE;   /* two numbers */
+                           num = grid(state,xx,yy);
+                       }
+                   }
+               }
+               if (num != area)
+                   valid = FALSE;
+
+               /*
+                * Now fill in the whole rectangle based on the
+                * value of `valid'.
+                */
+               for (xx = x; xx < x+rw; xx++) {
+                   for (yy = y; yy < y+rh; yy++) {
+                       index(state, ret, xx, yy) = valid;
+                   }
+               }
+           }
+
+    return ret;
+}
+
+game_state *make_move(game_state *from, int x, int y, int button)
+{
+    float xf, yf, dx, dy;
+    int hxr, hyr, vxr, vyr;
+    game_state *ret;
+
+    if (button != LEFT_BUTTON)
+       return NULL;
+
+    xf = FROMCOORD(((float)x));
+    yf = FROMCOORD(((float)y));
+
+    hxr = (int)xf;
+    hyr = (int)(yf + 0.5F);
+
+    vxr = (int)(xf + 0.5F);
+    vyr = (int)yf;
+
+    dx = fabs(xf - vxr);
+    dy = fabs(yf - hyr);
+
+    if (dy < dx && HRANGE(from,hxr,hyr)) {
+       ret = dup_game(from);
+       hedge(ret,hxr,hyr) = !hedge(ret,hxr,hyr);
+       return ret;
+    } else if (dx < dy && VRANGE(from,vxr,vyr)) {
+       ret = dup_game(from);
+       vedge(ret,vxr,vyr) = !vedge(ret,vxr,vyr);
+       return ret;
+    }
+
+    return NULL;
+}
+
+/* ----------------------------------------------------------------------
+ * Drawing routines.
+ */
+
+#define L 1
+#define R 2
+#define U 4
+#define D 8
+#define CORRECT 16
+
+struct game_drawstate {
+    int started;
+    int w, h;
+    unsigned char *visible;
+};
+
+void game_size(game_params *params, int *x, int *y)
+{
+    *x = params->w * TILE_SIZE + 2*BORDER + 1;
+    *y = params->h * TILE_SIZE + 2*BORDER + 1;
+}
+
+float *game_colours(frontend *fe, game_state *state, int *ncolours)
+{
+    float *ret = snewn(3 * NCOLOURS, float);
+
+    frontend_default_colour(fe, &ret[COL_BACKGROUND * 3]);
+
+    ret[COL_GRID * 3 + 0] = 0.5F * ret[COL_BACKGROUND * 3 + 0];
+    ret[COL_GRID * 3 + 1] = 0.5F * ret[COL_BACKGROUND * 3 + 1];
+    ret[COL_GRID * 3 + 2] = 0.5F * ret[COL_BACKGROUND * 3 + 2];
+
+    ret[COL_CORRECT * 3 + 0] = 0.75F * ret[COL_BACKGROUND * 3 + 0];
+    ret[COL_CORRECT * 3 + 1] = 0.75F * ret[COL_BACKGROUND * 3 + 1];
+    ret[COL_CORRECT * 3 + 2] = 0.75F * ret[COL_BACKGROUND * 3 + 2];
+
+    ret[COL_LINE * 3 + 0] = 0.0F;
+    ret[COL_LINE * 3 + 1] = 0.0F;
+    ret[COL_LINE * 3 + 2] = 0.0F;
+
+    ret[COL_TEXT * 3 + 0] = 0.0F;
+    ret[COL_TEXT * 3 + 1] = 0.0F;
+    ret[COL_TEXT * 3 + 2] = 0.0F;
+
+    *ncolours = NCOLOURS;
+    return ret;
+}
+
+game_drawstate *game_new_drawstate(game_state *state)
+{
+    struct game_drawstate *ds = snew(struct game_drawstate);
+
+    ds->started = FALSE;
+    ds->w = state->w;
+    ds->h = state->h;
+    ds->visible = snewn(ds->w * ds->h, unsigned char);
+    memset(ds->visible, 0xFF, ds->w * ds->h);
+
+    return ds;
+}
+
+void game_free_drawstate(game_drawstate *ds)
+{
+    sfree(ds->visible);
+    sfree(ds);
+}
+
+void draw_tile(frontend *fe, game_state *state, int x, int y, int correct)
+{
+    int cx = COORD(x), cy = COORD(y);
+    char str[80];
+
+    draw_rect(fe, cx, cy, TILE_SIZE+1, TILE_SIZE+1, COL_GRID);
+    draw_rect(fe, cx+1, cy+1, TILE_SIZE-1, TILE_SIZE-1,
+             correct ? COL_CORRECT : COL_BACKGROUND);
+
+    if (grid(state,x,y)) {
+       sprintf(str, "%d", grid(state,x,y));
+       draw_text(fe, cx+TILE_SIZE/2, cy+TILE_SIZE/2, FONT_VARIABLE,
+                 TILE_SIZE/3, ALIGN_HCENTRE | ALIGN_VCENTRE, COL_TEXT, str);
+    }
+
+    /*
+     * Draw edges.
+     */
+    if (!HRANGE(state,x,y) || hedge(state,x,y))
+       draw_rect(fe, cx, cy, TILE_SIZE+1, 2, COL_LINE);
+    if (!HRANGE(state,x,y+1) || hedge(state,x,y+1))
+       draw_rect(fe, cx, cy+TILE_SIZE-1, TILE_SIZE+1, 2, COL_LINE);
+    if (!VRANGE(state,x,y) || vedge(state,x,y))
+       draw_rect(fe, cx, cy, 2, TILE_SIZE+1, COL_LINE);
+    if (!VRANGE(state,x+1,y) || vedge(state,x+1,y))
+       draw_rect(fe, cx+TILE_SIZE-1, cy, 2, TILE_SIZE+1, COL_LINE);
+
+    /*
+     * Draw corners.
+     */
+    if ((HRANGE(state,x-1,y) && hedge(state,x-1,y)) ||
+       (VRANGE(state,x,y-1) && vedge(state,x,y-1)))
+       draw_rect(fe, cx, cy, 2, 2, COL_LINE);
+    if ((HRANGE(state,x+1,y) && hedge(state,x+1,y)) ||
+       (VRANGE(state,x+1,y-1) && vedge(state,x+1,y-1)))
+       draw_rect(fe, cx+TILE_SIZE-1, cy, 2, 2, COL_LINE);
+    if ((HRANGE(state,x-1,y+1) && hedge(state,x-1,y+1)) ||
+       (VRANGE(state,x,y+1) && vedge(state,x,y+1)))
+       draw_rect(fe, cx, cy+TILE_SIZE-1, 2, 2, COL_LINE);
+    if ((HRANGE(state,x+1,y+1) && hedge(state,x+1,y+1)) ||
+       (VRANGE(state,x+1,y+1) && vedge(state,x+1,y+1)))
+       draw_rect(fe, cx+TILE_SIZE-1, cy+TILE_SIZE-1, 2, 2, COL_LINE);
+
+    draw_update(fe, cx, cy, TILE_SIZE+1, TILE_SIZE+1);
+}
+
+void game_redraw(frontend *fe, game_drawstate *ds, game_state *oldstate,
+                 game_state *state, float animtime, float flashtime)
+{
+    int x, y;
+    unsigned char *correct;
+
+    correct = get_correct(state);
+
+    if (!ds->started) {
+       draw_rect(fe, COORD(0)-1, COORD(0)-1,
+                 ds->w*TILE_SIZE+3, ds->h*TILE_SIZE+3, COL_LINE);
+       ds->started = TRUE;
+    }
+
+    for (x = 0; x < state->w; x++)
+       for (y = 0; y < state->h; y++) {
+           unsigned char c = 0;
+
+           if (!HRANGE(state,x,y) || hedge(state,x,y))
+               c |= L;
+           if (!HRANGE(state,x+1,y) || hedge(state,x+1,y))
+               c |= R;
+           if (!VRANGE(state,x,y) || vedge(state,x,y))
+               c |= U;
+           if (!VRANGE(state,x,y+1) || vedge(state,x,y+1))
+               c |= D;
+           if (index(state, correct, x, y))
+               c |= CORRECT;
+
+           if (index(ds,ds->visible,x,y) != c) {
+               draw_tile(fe, state, x, y, c & CORRECT);
+               //index(ds,ds->visible,x,y) = c;
+           }
+       }
+
+    sfree(correct);
+}
+
+float game_anim_length(game_state *oldstate, game_state *newstate)
+{
+    return 0.0F;
+}
+
+float game_flash_length(game_state *oldstate, game_state *newstate)
+{
+    return 0.0F;
+}
+
+int game_wants_statusbar(void)
+{
+    return FALSE;
+}