1 files changed, 1214 insertions, 0 deletions

diff --git a/apps/plugins/puzzles/src/sixteen.c b/apps/plugins/puzzles/src/sixteen.c
new file mode 100644
index 0000000000..edc9771867
--- /dev/null
+++ b/apps/plugins/puzzles/src/sixteen.c
@@ -0,0 +1,1214 @@
+/*
+ * sixteen.c: `16-puzzle', a sliding-tiles jigsaw which differs
+ * from the 15-puzzle in that you toroidally rotate a row or column
+ * at a time.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include <ctype.h>
+#include <math.h>
+
+#include "puzzles.h"
+
+#define PREFERRED_TILE_SIZE 48
+#define TILE_SIZE (ds->tilesize)
+#define BORDER TILE_SIZE
+#define HIGHLIGHT_WIDTH (TILE_SIZE / 20)
+#define COORD(x)  ( (x) * TILE_SIZE + BORDER )
+#define FROMCOORD(x)  ( ((x) - BORDER + 2*TILE_SIZE) / TILE_SIZE - 2 )
+
+#define ANIM_TIME 0.13F
+#define FLASH_FRAME 0.13F
+
+#define X(state, i) ( (i) % (state)->w )
+#define Y(state, i) ( (i) / (state)->w )
+#define C(state, x, y) ( (y) * (state)->w + (x) )
+
+#define TILE_CURSOR(i, state, x, y) ((i) == C((state), (x), (y)) &&     \
+                                     0 <= (x) && (x) < (state)->w &&    \
+                                     0 <= (y) && (y) < (state)->h)
+enum {
+    COL_BACKGROUND,
+    COL_TEXT,
+    COL_HIGHLIGHT,
+    COL_LOWLIGHT,
+    NCOLOURS
+};
+
+struct game_params {
+    int w, h;
+    int movetarget;
+};
+
+struct game_state {
+    int w, h, n;
+    int *tiles;
+    int completed;
+    int used_solve;                    /* used to suppress completion flash */
+    int movecount, movetarget;
+    int last_movement_sense;
+};
+
+static game_params *default_params(void)
+{
+    game_params *ret = snew(game_params);
+
+    ret->w = ret->h = 4;
+    ret->movetarget = 0;
+
+    return ret;
+}
+
+static 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 = 3, h = 3; break;
+      case 1: w = 4, h = 3; break;
+      case 2: w = 4, h = 4; break;
+      case 3: w = 5, h = 4; break;
+      case 4: w = 5, h = 5; break;
+      default: return FALSE;
+    }
+
+    sprintf(buf, "%dx%d", w, h);
+    *name = dupstr(buf);
+    *params = ret = snew(game_params);
+    ret->w = w;
+    ret->h = h;
+    ret->movetarget = 0;
+    return TRUE;
+}
+
+static void free_params(game_params *params)
+{
+    sfree(params);
+}
+
+static game_params *dup_params(const game_params *params)
+{
+    game_params *ret = snew(game_params);
+    *ret = *params;                    /* structure copy */
+    return ret;
+}
+
+static void decode_params(game_params *ret, char const *string)
+{
+    ret->w = ret->h = atoi(string);
+    ret->movetarget = 0;
+    while (*string && isdigit((unsigned char)*string)) string++;
+    if (*string == 'x') {
+        string++;
+        ret->h = atoi(string);
+        while (*string && isdigit((unsigned char)*string))
+            string++;
+    }
+    if (*string == 'm') {
+        string++;
+        ret->movetarget = atoi(string);
+        while (*string && isdigit((unsigned char)*string))
+            string++;
+    }
+}
+
+static char *encode_params(const game_params *params, int full)
+{
+    char data[256];
+
+    sprintf(data, "%dx%d", params->w, params->h);
+    /* Shuffle limit is part of the limited parameters, because we have to
+     * supply the target move count. */
+    if (params->movetarget)
+        sprintf(data + strlen(data), "m%d", params->movetarget);
+
+    return dupstr(data);
+}
+
+static config_item *game_configure(const game_params *params)
+{
+    config_item *ret;
+    char buf[80];
+
+    ret = snewn(4, 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 = "Number of shuffling moves";
+    ret[2].type = C_STRING;
+    sprintf(buf, "%d", params->movetarget);
+    ret[2].sval = dupstr(buf);
+    ret[2].ival = 0;
+
+    ret[3].name = NULL;
+    ret[3].type = C_END;
+    ret[3].sval = NULL;
+    ret[3].ival = 0;
+
+    return ret;
+}
+
+static game_params *custom_params(const config_item *cfg)
+{
+    game_params *ret = snew(game_params);
+
+    ret->w = atoi(cfg[0].sval);
+    ret->h = atoi(cfg[1].sval);
+    ret->movetarget = atoi(cfg[2].sval);
+
+    return ret;
+}
+
+static char *validate_params(const game_params *params, int full)
+{
+    if (params->w < 2 || params->h < 2)
+        return "Width and height must both be at least two";
+
+    return NULL;
+}
+
+static int perm_parity(int *perm, int n)
+{
+    int i, j, ret;
+
+    ret = 0;
+
+    for (i = 0; i < n-1; i++)
+        for (j = i+1; j < n; j++)
+            if (perm[i] > perm[j])
+                ret = !ret;
+
+    return ret;
+}
+
+static char *new_game_desc(const game_params *params, random_state *rs,
+                           char **aux, int interactive)
+{
+    int stop, n, i, x;
+    int x1, x2, p1, p2;
+    int *tiles, *used;
+    char *ret;
+    int retlen;
+
+    n = params->w * params->h;
+
+    tiles = snewn(n, int);
+
+    if (params->movetarget) {
+        int prevoffset = -1;
+        int max = (params->w > params->h ? params->w : params->h);
+        int *prevmoves = snewn(max, int);
+
+        /*
+         * Shuffle the old-fashioned way, by making a series of
+         * single moves on the grid.
+         */
+
+        for (i = 0; i < n; i++)
+            tiles[i] = i;
+
+        for (i = 0; i < params->movetarget; i++) {
+            int start, offset, len, direction, index;
+            int j, tmp;
+
+            /*
+             * Choose a move to make. We can choose from any row
+             * or any column.
+             */
+            while (1) {
+                j = random_upto(rs, params->w + params->h);
+
+                if (j < params->w) {
+                    /* Column. */
+                    index = j;
+                    start = j;
+                    offset = params->w;
+                    len = params->h;
+                } else {
+                    /* Row. */
+                    index = j - params->w;
+                    start = index * params->w;
+                    offset = 1;
+                    len = params->w;
+                }
+
+                direction = -1 + 2 * random_upto(rs, 2);
+
+                /*
+                 * To at least _try_ to avoid boring cases, check
+                 * that this move doesn't directly undo a previous
+                 * one, or repeat it so many times as to turn it
+                 * into fewer moves in the opposite direction. (For
+                 * example, in a row of length 4, we're allowed to
+                 * move it the same way twice, but not three
+                 * times.)
+                 * 
+                 * We track this for each individual row/column,
+                 * and clear all the counters as soon as a
+                 * perpendicular move is made. This isn't perfect
+                 * (it _can't_ guaranteeably be perfect - there
+                 * will always come a move count beyond which a
+                 * shorter solution will be possible than the one
+                 * which constructed the position) but it should
+                 * sort out all the obvious cases.
+                 */
+                if (offset == prevoffset) {
+                    tmp = prevmoves[index] + direction;
+                    if (abs(2*tmp) > len || abs(tmp) < abs(prevmoves[index]))
+                        continue;
+                }
+
+                /* If we didn't `continue', we've found an OK move to make. */
+                if (offset != prevoffset) {
+                    int i;
+                    for (i = 0; i < max; i++)
+                        prevmoves[i] = 0;
+                    prevoffset = offset;
+                }
+                prevmoves[index] += direction;
+                break;
+            }
+
+            /*
+             * Make the move.
+             */
+            if (direction < 0) {
+                start += (len-1) * offset;
+                offset = -offset;
+            }
+            tmp = tiles[start];
+            for (j = 0; j+1 < len; j++)
+                tiles[start + j*offset] = tiles[start + (j+1)*offset];
+            tiles[start + (len-1) * offset] = tmp;
+        }
+
+        sfree(prevmoves);
+
+    } else {
+
+        used = snewn(n, int);
+
+        for (i = 0; i < n; i++) {
+            tiles[i] = -1;
+            used[i] = FALSE;
+        }
+
+        /*
+         * If both dimensions are odd, there is a parity
+         * constraint.
+         */
+        if (params->w & params->h & 1)
+            stop = 2;
+        else
+            stop = 0;
+
+        /*
+         * Place everything except (possibly) the last two tiles.
+         */
+        for (x = 0, i = n; i > stop; i--) {
+            int k = i > 1 ? random_upto(rs, i) : 0;
+            int j;
+
+            for (j = 0; j < n; j++)
+                if (!used[j] && (k-- == 0))
+                    break;
+
+            assert(j < n && !used[j]);
+            used[j] = TRUE;
+
+            while (tiles[x] >= 0)
+                x++;
+            assert(x < n);
+            tiles[x] = j;
+        }
+
+        if (stop) {
+            /*
+             * Find the last two locations, and the last two
+             * pieces.
+             */
+            while (tiles[x] >= 0)
+                x++;
+            assert(x < n);
+            x1 = x;
+            x++;
+            while (tiles[x] >= 0)
+                x++;
+            assert(x < n);
+            x2 = x;
+
+            for (i = 0; i < n; i++)
+                if (!used[i])
+                    break;
+            p1 = i;
+            for (i = p1+1; i < n; i++)
+                if (!used[i])
+                    break;
+            p2 = i;
+
+            /*
+             * Try the last two tiles one way round. If that fails,
+             * swap them.
+             */
+            tiles[x1] = p1;
+            tiles[x2] = p2;
+            if (perm_parity(tiles, n) != 0) {
+                tiles[x1] = p2;
+                tiles[x2] = p1;
+                assert(perm_parity(tiles, n) == 0);
+            }
+        }
+
+        sfree(used);
+    }
+
+    /*
+     * Now construct the game description, by describing the tile
+     * array as a simple sequence of comma-separated integers.
+     */
+    ret = NULL;
+    retlen = 0;
+    for (i = 0; i < n; i++) {
+        char buf[80];
+        int k;
+
+        k = sprintf(buf, "%d,", tiles[i]+1);
+
+        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(const game_params *params, const char *desc)
+{
+    const char *p;
+    char *err;
+    int i, area;
+    int *used;
+
+    area = params->w * params->h;
+    p = desc;
+    err = NULL;
+
+    used = snewn(area, int);
+    for (i = 0; i < area; i++)
+        used[i] = FALSE;
+
+    for (i = 0; i < area; i++) {
+        const char *q = p;
+        int n;
+
+        if (*p < '0' || *p > '9') {
+            err = "Not enough numbers in string";
+            goto leave;
+        }
+        while (*p >= '0' && *p <= '9')
+            p++;
+        if (i < area-1 && *p != ',') {
+            err = "Expected comma after number";
+            goto leave;
+        }
+        else if (i == area-1 && *p) {
+            err = "Excess junk at end of string";
+            goto leave;
+        }
+        n = atoi(q);
+        if (n < 1 || n > area) {
+            err = "Number out of range";
+            goto leave;
+        }
+        if (used[n-1]) {
+            err = "Number used twice";
+            goto leave;
+        }
+        used[n-1] = TRUE;
+
+        if (*p) p++;                   /* eat comma */
+    }
+
+    leave:
+    sfree(used);
+    return err;
+}
+
+static game_state *new_game(midend *me, const game_params *params,
+                            const char *desc)
+{
+    game_state *state = snew(game_state);
+    int i;
+    const char *p;
+
+    state->w = params->w;
+    state->h = params->h;
+    state->n = params->w * params->h;
+    state->tiles = snewn(state->n, int);
+
+    p = desc;
+    i = 0;
+    for (i = 0; i < state->n; i++) {
+        assert(*p);
+        state->tiles[i] = atoi(p);
+        while (*p && *p != ',')
+            p++;
+        if (*p) p++;                   /* eat comma */
+    }
+    assert(!*p);
+
+    state->completed = state->movecount = 0;
+    state->movetarget = params->movetarget;
+    state->used_solve = FALSE;
+    state->last_movement_sense = 0;
+
+    return state;
+}
+
+static game_state *dup_game(const game_state *state)
+{
+    game_state *ret = snew(game_state);
+
+    ret->w = state->w;
+    ret->h = state->h;
+    ret->n = state->n;
+    ret->tiles = snewn(state->w * state->h, int);
+    memcpy(ret->tiles, state->tiles, state->w * state->h * sizeof(int));
+    ret->completed = state->completed;
+    ret->movecount = state->movecount;
+    ret->movetarget = state->movetarget;
+    ret->used_solve = state->used_solve;
+    ret->last_movement_sense = state->last_movement_sense;
+
+    return ret;
+}
+
+static void free_game(game_state *state)
+{
+    sfree(state->tiles);
+    sfree(state);
+}
+
+static char *solve_game(const game_state *state, const game_state *currstate,
+                        const char *aux, char **error)
+{
+    return dupstr("S");
+}
+
+static int game_can_format_as_text_now(const game_params *params)
+{
+    return TRUE;
+}
+
+static char *game_text_format(const game_state *state)
+{
+    char *ret, *p, buf[80];
+    int x, y, col, maxlen;
+
+    /*
+     * First work out how many characters we need to display each
+     * number.
+     */
+    col = sprintf(buf, "%d", state->n);
+
+    /*
+     * Now we know the exact total size of the grid we're going to
+     * produce: it's got h rows, each containing w lots of col, w-1
+     * spaces and a trailing newline.
+     */
+    maxlen = state->h * state->w * (col+1);
+
+    ret = snewn(maxlen+1, char);
+    p = ret;
+
+    for (y = 0; y < state->h; y++) {
+        for (x = 0; x < state->w; x++) {
+            int v = state->tiles[state->w*y+x];
+            sprintf(buf, "%*d", col, v);
+            memcpy(p, buf, col);
+            p += col;
+            if (x+1 == state->w)
+                *p++ = '\n';
+            else
+                *p++ = ' ';
+        }
+    }
+
+    assert(p - ret == maxlen);
+    *p = '\0';
+    return ret;
+}
+
+enum cursor_mode { unlocked, lock_tile, lock_position };
+
+struct game_ui {
+    int cur_x, cur_y;
+    int cur_visible;
+    enum cursor_mode cur_mode;
+};
+
+static game_ui *new_ui(const game_state *state)
+{
+    game_ui *ui = snew(game_ui);
+    ui->cur_x = 0;
+    ui->cur_y = 0;
+    ui->cur_visible = FALSE;
+    ui->cur_mode = unlocked;
+
+    return ui;
+}
+
+static void free_ui(game_ui *ui)
+{
+    sfree(ui);
+}
+
+static char *encode_ui(const game_ui *ui)
+{
+    return NULL;
+}
+
+static void decode_ui(game_ui *ui, const char *encoding)
+{
+}
+
+static void game_changed_state(game_ui *ui, const game_state *oldstate,
+                               const game_state *newstate)
+{
+}
+
+struct game_drawstate {
+    int started;
+    int w, h, bgcolour;
+    int *tiles;
+    int tilesize;
+    int cur_x, cur_y;
+};
+
+static char *interpret_move(const game_state *state, game_ui *ui,
+                            const game_drawstate *ds,
+                            int x, int y, int button)
+{
+    int cx = -1, cy = -1, dx, dy;
+    char buf[80];
+    int shift = button & MOD_SHFT, control = button & MOD_CTRL,
+        pad = button & MOD_NUM_KEYPAD;
+
+    button &= ~MOD_MASK;
+
+    if (IS_CURSOR_MOVE(button) || pad) {
+        if (!ui->cur_visible) {
+            ui->cur_visible = 1;
+            return "";
+        }
+
+        if (control || shift || ui->cur_mode) {
+            int x = ui->cur_x, y = ui->cur_y, xwrap = x, ywrap = y;
+            if (x < 0 || x >= state->w || y < 0 || y >= state->h)
+                return NULL;
+            move_cursor(button | pad, &x, &y,
+                        state->w, state->h, FALSE);
+            move_cursor(button | pad, &xwrap, &ywrap,
+                        state->w, state->h, TRUE);
+
+            if (x != xwrap) {
+                sprintf(buf, "R%d,%c1", y, x ? '+' : '-');
+            } else if (y != ywrap) {
+                sprintf(buf, "C%d,%c1", x, y ? '+' : '-');
+            } else if (x == ui->cur_x)
+                sprintf(buf, "C%d,%d", x, y - ui->cur_y);
+            else
+                sprintf(buf, "R%d,%d", y, x - ui->cur_x);
+
+            if (control || (!shift && ui->cur_mode == lock_tile)) {
+                ui->cur_x = xwrap;
+                ui->cur_y = ywrap;
+            }
+
+            return dupstr(buf);
+        } else {
+            int x = ui->cur_x + 1, y = ui->cur_y + 1;
+
+            move_cursor(button | pad, &x, &y,
+                        state->w + 2, state->h + 2, FALSE);
+
+            if (x == 0 && y == 0) {
+                int t = ui->cur_x;
+                ui->cur_x = ui->cur_y;
+                ui->cur_y = t;
+            } else if (x == 0 && y == state->h + 1) {
+                int t = ui->cur_x;
+                ui->cur_x = (state->h - 1) - ui->cur_y;
+                ui->cur_y = (state->h - 1) - t;
+            } else if (x == state->w + 1 && y == 0) {
+                int t = ui->cur_x;
+                ui->cur_x = (state->w - 1) - ui->cur_y;
+                ui->cur_y = (state->w - 1) - t;
+            } else if (x == state->w + 1 && y == state->h + 1) {
+                int t = ui->cur_x;
+                ui->cur_x = state->w - state->h + ui->cur_y;
+                ui->cur_y = state->h - state->w + t;
+            } else {
+                ui->cur_x = x - 1;
+                ui->cur_y = y - 1;
+            }
+
+            ui->cur_visible = 1;
+            return "";
+        }
+    }
+
+    if (button == LEFT_BUTTON || button == RIGHT_BUTTON) {
+        cx = FROMCOORD(x);
+        cy = FROMCOORD(y);
+        ui->cur_visible = 0;
+    } else if (IS_CURSOR_SELECT(button)) {
+        if (ui->cur_visible) {
+            if (ui->cur_x == -1 || ui->cur_x == state->w ||
+                ui->cur_y == -1 || ui->cur_y == state->h) {
+                cx = ui->cur_x;
+                cy = ui->cur_y;
+            } else {
+                const enum cursor_mode m = (button == CURSOR_SELECT2 ?
+                                            lock_position : lock_tile);
+                ui->cur_mode = (ui->cur_mode == m ? unlocked : m);
+                return "";
+            }
+        } else {
+            ui->cur_visible = 1;
+            return "";
+        }
+    } else {
+        return NULL;
+    }
+
+    if (cx == -1 && cy >= 0 && cy < state->h)
+        dx = -1, dy = 0;
+    else if (cx == state->w && cy >= 0 && cy < state->h)
+        dx = +1, dy = 0;
+    else if (cy == -1 && cx >= 0 && cx < state->w)
+        dy = -1, dx = 0;
+    else if (cy == state->h && cx >= 0 && cx < state->w)
+        dy = +1, dx = 0;
+    else
+        return "";                   /* invalid click location */
+
+    /* reverse direction if right hand button is pressed */
+    if (button == RIGHT_BUTTON || button == CURSOR_SELECT2) {
+        dx = -dx;
+        dy = -dy;
+    }
+
+    if (dx)
+        sprintf(buf, "R%d,%d", cy, dx);
+    else
+        sprintf(buf, "C%d,%d", cx, dy);
+    return dupstr(buf);
+}
+
+static game_state *execute_move(const game_state *from, const char *move)
+{
+    int cx, cy, dx, dy;
+    int tx, ty, n;
+    game_state *ret;
+
+    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.
+         */
+        for (i = 0; i < ret->n; i++)
+            ret->tiles[i] = i+1;
+        ret->used_solve = TRUE;
+        ret->completed = ret->movecount = 1;
+
+        return ret;
+    }
+
+    if (move[0] == 'R' && sscanf(move+1, "%d,%d", &cy, &dx) == 2 &&
+        cy >= 0 && cy < from->h) {
+        cx = dy = 0;
+        n = from->w;
+    } else if (move[0] == 'C' && sscanf(move+1, "%d,%d", &cx, &dy) == 2 &&
+               cx >= 0 && cx < from->w) {
+        cy = dx = 0;
+        n = from->h;
+    } else
+        return NULL;
+
+    ret = dup_game(from);
+
+    do {
+        tx = (cx - dx + from->w) % from->w;
+        ty = (cy - dy + from->h) % from->h;
+        ret->tiles[C(ret, cx, cy)] = from->tiles[C(from, tx, ty)];
+        cx = tx;
+        cy = ty;
+    } while (--n > 0);
+
+    ret->movecount++;
+
+    ret->last_movement_sense = dx+dy;
+
+    /*
+     * See if the game has been completed.
+     */
+    if (!ret->completed) {
+        ret->completed = ret->movecount;
+        for (n = 0; n < ret->n; n++)
+            if (ret->tiles[n] != n+1)
+                ret->completed = FALSE;
+    }
+
+    return ret;
+}
+
+/* ----------------------------------------------------------------------
+ * Drawing routines.
+ */
+
+static void game_compute_size(const game_params *params, int tilesize,
+                              int *x, int *y)
+{
+    /* Ick: fake up `ds->tilesize' for macro expansion purposes */
+    struct { int tilesize; } ads, *ds = &ads;
+    ads.tilesize = tilesize;
+
+    *x = TILE_SIZE * params->w + 2 * BORDER;
+    *y = TILE_SIZE * params->h + 2 * BORDER;
+}
+
+static void game_set_size(drawing *dr, game_drawstate *ds,
+                          const game_params *params, int tilesize)
+{
+    ds->tilesize = tilesize;
+}
+
+static float *game_colours(frontend *fe, int *ncolours)
+{
+    float *ret = snewn(3 * NCOLOURS, float);
+    int i;
+
+    game_mkhighlight(fe, ret, COL_BACKGROUND, COL_HIGHLIGHT, COL_LOWLIGHT);
+
+    for (i = 0; i < 3; i++)
+        ret[COL_TEXT * 3 + i] = 0.0;
+
+    *ncolours = NCOLOURS;
+    return ret;
+}
+
+static game_drawstate *game_new_drawstate(drawing *dr, const game_state *state)
+{
+    struct game_drawstate *ds = snew(struct game_drawstate);
+    int i;
+
+    ds->started = FALSE;
+    ds->w = state->w;
+    ds->h = state->h;
+    ds->bgcolour = COL_BACKGROUND;
+    ds->tiles = snewn(ds->w*ds->h, int);
+    ds->tilesize = 0;                  /* haven't decided yet */
+    for (i = 0; i < ds->w*ds->h; i++)
+        ds->tiles[i] = -1;
+    ds->cur_x = ds->cur_y = -1;
+
+    return ds;
+}
+
+static void game_free_drawstate(drawing *dr, game_drawstate *ds)
+{
+    sfree(ds->tiles);
+    sfree(ds);
+}
+
+static void draw_tile(drawing *dr, game_drawstate *ds,
+                      const game_state *state, int x, int y,
+                      int tile, int flash_colour)
+{
+    if (tile == 0) {
+        draw_rect(dr, x, y, TILE_SIZE, TILE_SIZE,
+                  flash_colour);
+    } else {
+        int coords[6];
+        char str[40];
+
+        coords[0] = x + TILE_SIZE - 1;
+        coords[1] = y + TILE_SIZE - 1;
+        coords[2] = x + TILE_SIZE - 1;
+        coords[3] = y;
+        coords[4] = x;
+        coords[5] = y + TILE_SIZE - 1;
+        draw_polygon(dr, coords, 3, COL_LOWLIGHT, COL_LOWLIGHT);
+
+        coords[0] = x;
+        coords[1] = y;
+        draw_polygon(dr, coords, 3, COL_HIGHLIGHT, COL_HIGHLIGHT);
+
+        draw_rect(dr, x + HIGHLIGHT_WIDTH, y + HIGHLIGHT_WIDTH,
+                  TILE_SIZE - 2*HIGHLIGHT_WIDTH, TILE_SIZE - 2*HIGHLIGHT_WIDTH,
+                  flash_colour);
+
+        sprintf(str, "%d", tile);
+        draw_text(dr, x + TILE_SIZE/2, y + TILE_SIZE/2,
+                  FONT_VARIABLE, TILE_SIZE/3, ALIGN_VCENTRE | ALIGN_HCENTRE,
+                  COL_TEXT, str);
+    }
+    draw_update(dr, x, y, TILE_SIZE, TILE_SIZE);
+}
+
+static void draw_arrow(drawing *dr, game_drawstate *ds,
+                       int x, int y, int xdx, int xdy, int cur)
+{
+    int coords[14];
+    int ydy = -xdx, ydx = xdy;
+
+#define POINT(n, xx, yy) ( \
+    coords[2*(n)+0] = x + (xx)*xdx + (yy)*ydx, \
+    coords[2*(n)+1] = y + (xx)*xdy + (yy)*ydy)
+
+    POINT(0, TILE_SIZE / 2, 3 * TILE_SIZE / 4);   /* top of arrow */
+    POINT(1, 3 * TILE_SIZE / 4, TILE_SIZE / 2);   /* right corner */
+    POINT(2, 5 * TILE_SIZE / 8, TILE_SIZE / 2);   /* right concave */
+    POINT(3, 5 * TILE_SIZE / 8, TILE_SIZE / 4);   /* bottom right */
+    POINT(4, 3 * TILE_SIZE / 8, TILE_SIZE / 4);   /* bottom left */
+    POINT(5, 3 * TILE_SIZE / 8, TILE_SIZE / 2);   /* left concave */
+    POINT(6,     TILE_SIZE / 4, TILE_SIZE / 2);   /* left corner */
+
+    draw_polygon(dr, coords, 7, cur ? COL_HIGHLIGHT : COL_LOWLIGHT, COL_TEXT);
+}
+
+static void draw_arrow_for_cursor(drawing *dr, game_drawstate *ds,
+                                  int cur_x, int cur_y, int cur)
+{
+    if (cur_x == -1 && cur_y == -1)
+        return; /* 'no cursur here */
+    else if (cur_x == -1) /* LH column. */
+        draw_arrow(dr, ds, COORD(0), COORD(cur_y+1), 0, -1, cur);
+    else if (cur_x == ds->w) /* RH column */
+        draw_arrow(dr, ds, COORD(ds->w), COORD(cur_y), 0, +1, cur);
+    else if (cur_y == -1) /* Top row */
+        draw_arrow(dr, ds, COORD(cur_x), COORD(0), +1, 0, cur);
+    else if (cur_y == ds->h) /* Bottom row */
+        draw_arrow(dr, ds, COORD(cur_x+1), COORD(ds->h), -1, 0, cur);
+    else
+        return;
+
+    draw_update(dr, COORD(cur_x), COORD(cur_y),
+                TILE_SIZE, TILE_SIZE);
+}
+
+static void game_redraw(drawing *dr, game_drawstate *ds,
+                        const game_state *oldstate, const game_state *state,
+                        int dir, const game_ui *ui,
+                        float animtime, float flashtime)
+{
+    int i, bgcolour;
+    int cur_x = -1, cur_y = -1;
+
+    if (flashtime > 0) {
+        int frame = (int)(flashtime / FLASH_FRAME);
+        bgcolour = (frame % 2 ? COL_LOWLIGHT : COL_HIGHLIGHT);
+    } else
+        bgcolour = COL_BACKGROUND;
+
+    if (!ds->started) {
+        int coords[10];
+
+        draw_rect(dr, 0, 0,
+                  TILE_SIZE * state->w + 2 * BORDER,
+                  TILE_SIZE * state->h + 2 * BORDER, COL_BACKGROUND);
+        draw_update(dr, 0, 0,
+                    TILE_SIZE * state->w + 2 * BORDER,
+                    TILE_SIZE * state->h + 2 * BORDER);
+
+        /*
+         * Recessed area containing the whole puzzle.
+         */
+        coords[0] = COORD(state->w) + HIGHLIGHT_WIDTH - 1;
+        coords[1] = COORD(state->h) + HIGHLIGHT_WIDTH - 1;
+        coords[2] = COORD(state->w) + HIGHLIGHT_WIDTH - 1;
+        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->h) + HIGHLIGHT_WIDTH - 1;
+        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);
+
+        /*
+         * Arrows for making moves.
+         */
+        for (i = 0; i < state->w; i++) {
+            draw_arrow(dr, ds, COORD(i), COORD(0), +1, 0, 0);
+            draw_arrow(dr, ds, COORD(i+1), COORD(state->h), -1, 0, 0);
+        }
+        for (i = 0; i < state->h; i++) {
+            draw_arrow(dr, ds, COORD(state->w), COORD(i), 0, +1, 0);
+            draw_arrow(dr, ds, COORD(0), COORD(i+1), 0, -1, 0);
+        }
+
+        ds->started = TRUE;
+    }
+    /*
+     * Cursor (highlighted arrow around edge)
+     */
+    if (ui->cur_visible) {
+        cur_x = ui->cur_x; cur_y = ui->cur_y;
+    }
+
+    if (cur_x != ds->cur_x || cur_y != ds->cur_y) {
+        /* Cursor has changed; redraw two (prev and curr) arrows. */
+        draw_arrow_for_cursor(dr, ds, cur_x, cur_y, 1);
+        draw_arrow_for_cursor(dr, ds, ds->cur_x, ds->cur_y, 0);
+    }
+
+    /*
+     * Now draw each tile.
+     */
+
+    clip(dr, COORD(0), COORD(0), TILE_SIZE*state->w, TILE_SIZE*state->h);
+
+    for (i = 0; i < state->n; i++) {
+        int t, t0;
+        /*
+         * Figure out what should be displayed at this
+         * location. It's either a simple tile, or it's a
+         * transition between two tiles (in which case we say
+         * -1 because it must always be drawn).
+         */
+
+        if (oldstate && oldstate->tiles[i] != state->tiles[i])
+            t = -1;
+        else
+            t = state->tiles[i];
+
+        t0 = t;
+
+        if (ds->bgcolour != bgcolour ||   /* always redraw when flashing */
+            ds->tiles[i] != t || ds->tiles[i] == -1 || t == -1 ||
+            ((ds->cur_x != cur_x || ds->cur_y != cur_y) && /* cursor moved */
+             (TILE_CURSOR(i, state, ds->cur_x, ds->cur_y) ||
+              TILE_CURSOR(i, state, cur_x, cur_y)))) {
+            int x, y, x2, y2;
+
+            /*
+             * Figure out what to _actually_ draw, and where to
+             * draw it.
+             */
+            if (t == -1) {
+                int x0, y0, x1, y1, dx, dy;
+                int j;
+                float c;
+                int sense;
+
+                if (dir < 0) {
+                    assert(oldstate);
+                    sense = -oldstate->last_movement_sense;
+                } else {
+                    sense = state->last_movement_sense;
+                }
+
+                t = state->tiles[i];
+
+                /*
+                 * FIXME: must be prepared to draw a double
+                 * tile in some situations.
+                 */
+
+                /*
+                 * Find the coordinates of this tile in the old and
+                 * new states.
+                 */
+                x1 = COORD(X(state, i));
+                y1 = COORD(Y(state, i));
+                for (j = 0; j < oldstate->n; j++)
+                    if (oldstate->tiles[j] == state->tiles[i])
+                        break;
+                assert(j < oldstate->n);
+                x0 = COORD(X(state, j));
+                y0 = COORD(Y(state, j));
+
+                dx = (x1 - x0);
+                if (dx != 0 &&
+                    dx != TILE_SIZE * sense) {
+                    dx = (dx < 0 ? dx + TILE_SIZE * state->w :
+                          dx - TILE_SIZE * state->w);
+                    assert(abs(dx) == TILE_SIZE);
+                }
+                dy = (y1 - y0);
+                if (dy != 0 &&
+                    dy != TILE_SIZE * sense) {
+                    dy = (dy < 0 ? dy + TILE_SIZE * state->h :
+                          dy - TILE_SIZE * state->h);
+                    assert(abs(dy) == TILE_SIZE);
+                }
+
+                c = (animtime / ANIM_TIME);
+                if (c < 0.0F) c = 0.0F;
+                if (c > 1.0F) c = 1.0F;
+
+                x = x0 + (int)(c * dx);
+                y = y0 + (int)(c * dy);
+                x2 = x1 - dx + (int)(c * dx);
+                y2 = y1 - dy + (int)(c * dy);
+            } else {
+                x = COORD(X(state, i));
+                y = COORD(Y(state, i));
+                x2 = y2 = -1;
+            }
+
+            draw_tile(dr, ds, state, x, y, t,
+                      (x2 == -1 && TILE_CURSOR(i, state, cur_x, cur_y)) ?
+                      COL_LOWLIGHT : bgcolour);
+
+            if (x2 != -1 || y2 != -1)
+                draw_tile(dr, ds, state, x2, y2, t, bgcolour);
+        }
+        ds->tiles[i] = t0;
+    }
+
+    ds->cur_x = cur_x;
+    ds->cur_y = cur_y;
+
+    unclip(dr);
+
+    ds->bgcolour = bgcolour;
+
+    /*
+     * Update the status bar.
+     */
+    {
+        char statusbuf[256];
+
+        /*
+         * Don't show the new status until we're also showing the
+         * new _state_ - after the game animation is complete.
+         */
+        if (oldstate)
+            state = oldstate;
+
+        if (state->used_solve)
+            sprintf(statusbuf, "Moves since auto-solve: %d",
+                    state->movecount - state->completed);
+        else {
+            sprintf(statusbuf, "%sMoves: %d",
+                    (state->completed ? "COMPLETED! " : ""),
+                    (state->completed ? state->completed : state->movecount));
+            if (state->movetarget)
+                sprintf(statusbuf+strlen(statusbuf), " (target %d)",
+                        state->movetarget);
+        }
+
+        status_bar(dr, statusbuf);
+    }
+}
+
+static float game_anim_length(const game_state *oldstate,
+                              const game_state *newstate, int dir, game_ui *ui)
+{
+    return ANIM_TIME;
+}
+
+static float game_flash_length(const game_state *oldstate,
+                               const game_state *newstate, int dir, game_ui *ui)
+{
+    if (!oldstate->completed && newstate->completed &&
+        !oldstate->used_solve && !newstate->used_solve)
+        return 2 * FLASH_FRAME;
+    else
+        return 0.0F;
+}
+
+static int game_status(const game_state *state)
+{
+    return state->completed ? +1 : 0;
+}
+
+static int game_timing_state(const game_state *state, game_ui *ui)
+{
+    return TRUE;
+}
+
+static void game_print_size(const game_params *params, float *x, float *y)
+{
+}
+
+static void game_print(drawing *dr, const game_state *state, int tilesize)
+{
+}
+
+#ifdef COMBINED
+#define thegame sixteen
+#endif
+
+const struct game thegame = {
+    "Sixteen", "games.sixteen", "sixteen",
+    default_params,
+    game_fetch_preset, NULL,
+    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,
+    TRUE, solve_game,
+    TRUE, game_can_format_as_text_now, 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,
+    game_status,
+    FALSE, FALSE, game_print_size, game_print,
+    TRUE,                              /* wants_statusbar */
+    FALSE, game_timing_state,
+    0,                                 /* flags */
+};
+
+/* vim: set shiftwidth=4 tabstop=8: */