+ sprintf(buf, "M%d,%d,%d", x, y, dir);
+ return dupstr(buf);
+}
+
+static game_state *execute_move(game_state *from, char *move)
+{
+ game_state *ret;
+ int w = from->w, h = from->h, n = from->n, wh = w*h;
+ int x, y, dir;
+
+ if (!strcmp(move, "S")) {
+ int i;
+ ret = dup_game(from);
+
+ /*
+ * Simply replace the grid with a solved one. For this game,
+ * this isn't a useful operation for actually telling the user
+ * what they should have done, but it is useful for
+ * conveniently being able to get hold of a clean state from
+ * which to practise manoeuvres.
+ */
+ qsort(ret->grid, ret->w*ret->h, sizeof(int), compare_int);
+ for (i = 0; i < ret->w*ret->h; i++)
+ ret->grid[i] &= ~3;
+ ret->used_solve = TRUE;
+ ret->completed = ret->movecount = 1;
+
+ return ret;
+ }
+
+ if (move[0] != 'M' ||
+ sscanf(move+1, "%d,%d,%d", &x, &y, &dir) != 3 ||
+ x < 0 || y < 0 || x > from->w - n || y > from->h - n)
+ return NULL; /* can't parse this move string */
+