puzzles: refactor and resync with upstream

This brings puzzles up-to-date with upstream revision
2d333750272c3967cfd5cd3677572cddeaad5932, though certain changes made
by me, including cursor-only Untangle and some compilation fixes
remain. Upstream code has been moved to its separate subdirectory and
future syncs can be done by simply copying over the new sources.

Change-Id: Ia6506ca5f78c3627165ea6791d38db414ace0804

1 files changed, 1319 insertions, 0 deletions

diff --git a/apps/plugins/puzzles/src/twiddle.c b/apps/plugins/puzzles/src/twiddle.c
new file mode 100644
index 0000000000..6e05f4ddec
--- /dev/null
+++ b/apps/plugins/puzzles/src/twiddle.c
@@ -0,0 +1,1319 @@
+/*
+ * twiddle.c: Puzzle involving rearranging a grid of squares by
+ * rotating subsquares. Adapted and generalised from a
+ * door-unlocking puzzle in Metroid Prime 2 (the one in the Main
+ * Gyro Chamber).
+ */
+
+#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 / 2)
+#define HIGHLIGHT_WIDTH (TILE_SIZE / 20)
+#define COORD(x)  ( (x) * TILE_SIZE + BORDER )
+#define FROMCOORD(x)  ( ((x) - BORDER + TILE_SIZE) / TILE_SIZE - 1 )
+
+#define ANIM_PER_BLKSIZE_UNIT 0.13F
+#define FLASH_FRAME 0.13F
+
+enum {
+    COL_BACKGROUND,
+    COL_TEXT,
+    COL_HIGHLIGHT,
+    COL_HIGHLIGHT_GENTLE,
+    COL_LOWLIGHT,
+    COL_LOWLIGHT_GENTLE,
+    COL_HIGHCURSOR, COL_LOWCURSOR,
+    NCOLOURS
+};
+
+struct game_params {
+    int w, h, n;
+    int rowsonly;
+    int orientable;
+    int movetarget;
+};
+
+struct game_state {
+    int w, h, n;
+    int orientable;
+    int *grid;
+    int completed;
+    int used_solve;                    /* used to suppress completion flash */
+    int movecount, movetarget;
+    int lastx, lasty, lastr;           /* coordinates of last rotation */
+};
+
+static game_params *default_params(void)
+{
+    game_params *ret = snew(game_params);
+
+    ret->w = ret->h = 3;
+    ret->n = 2;
+    ret->rowsonly = ret->orientable = FALSE;
+    ret->movetarget = 0;
+
+    return ret;
+}
+
+
+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 int game_fetch_preset(int i, char **name, game_params **params)
+{
+    static struct {
+        char *title;
+        game_params params;
+    } presets[] = {
+        { "3x3 rows only", { 3, 3, 2, TRUE, FALSE } },
+        { "3x3 normal", { 3, 3, 2, FALSE, FALSE } },
+        { "3x3 orientable", { 3, 3, 2, FALSE, TRUE } },
+        { "4x4 normal", { 4, 4, 2, FALSE } },
+        { "4x4 orientable", { 4, 4, 2, FALSE, TRUE } },
+        { "4x4, rotating 3x3 blocks", { 4, 4, 3, FALSE } },
+        { "5x5, rotating 3x3 blocks", { 5, 5, 3, FALSE } },
+        { "6x6, rotating 4x4 blocks", { 6, 6, 4, FALSE } },
+    };
+
+    if (i < 0 || i >= lenof(presets))
+        return FALSE;
+
+    *name = dupstr(presets[i].title);
+    *params = dup_params(&presets[i].params);
+
+    return TRUE;
+}
+
+static void decode_params(game_params *ret, char const *string)
+{
+    ret->w = ret->h = atoi(string);
+    ret->n = 2;
+    ret->rowsonly = ret->orientable = FALSE;
+    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 == 'n') {
+        string++;
+        ret->n = atoi(string);
+        while (*string && isdigit((unsigned char)*string)) string++;
+    }
+    while (*string) {
+        if (*string == 'r') {
+            ret->rowsonly = TRUE;
+        } else if (*string == 'o') {
+            ret->orientable = TRUE;
+        } else if (*string == 'm') {
+            string++;
+            ret->movetarget = atoi(string);
+            while (string[1] && isdigit((unsigned char)string[1])) string++;
+        }
+        string++;
+    }
+}
+
+static char *encode_params(const game_params *params, int full)
+{
+    char buf[256];
+    sprintf(buf, "%dx%dn%d%s%s", params->w, params->h, params->n,
+            params->rowsonly ? "r" : "",
+            params->orientable ? "o" : "");
+    /* Shuffle limit is part of the limited parameters, because we have to
+     * supply the target move count. */
+    if (params->movetarget)
+        sprintf(buf + strlen(buf), "m%d", params->movetarget);
+    return dupstr(buf);
+}
+
+static config_item *game_configure(const game_params *params)
+{
+    config_item *ret;
+    char buf[80];
+
+    ret = snewn(7, 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 = "Rotating block size";
+    ret[2].type = C_STRING;
+    sprintf(buf, "%d", params->n);
+    ret[2].sval = dupstr(buf);
+    ret[2].ival = 0;
+
+    ret[3].name = "One number per row";
+    ret[3].type = C_BOOLEAN;
+    ret[3].sval = NULL;
+    ret[3].ival = params->rowsonly;
+
+    ret[4].name = "Orientation matters";
+    ret[4].type = C_BOOLEAN;
+    ret[4].sval = NULL;
+    ret[4].ival = params->orientable;
+
+    ret[5].name = "Number of shuffling moves";
+    ret[5].type = C_STRING;
+    sprintf(buf, "%d", params->movetarget);
+    ret[5].sval = dupstr(buf);
+    ret[5].ival = 0;
+
+    ret[6].name = NULL;
+    ret[6].type = C_END;
+    ret[6].sval = NULL;
+    ret[6].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->n = atoi(cfg[2].sval);
+    ret->rowsonly = cfg[3].ival;
+    ret->orientable = cfg[4].ival;
+    ret->movetarget = atoi(cfg[5].sval);
+
+    return ret;
+}
+
+static char *validate_params(const game_params *params, int full)
+{
+    if (params->n < 2)
+        return "Rotating block size must be at least two";
+    if (params->w < params->n)
+        return "Width must be at least the rotating block size";
+    if (params->h < params->n)
+        return "Height must be at least the rotating block size";
+    return NULL;
+}
+
+/*
+ * This function actually performs a rotation on a grid. The `x'
+ * and `y' coordinates passed in are the coordinates of the _top
+ * left corner_ of the rotated region. (Using the centre would have
+ * involved half-integers and been annoyingly fiddly. Clicking in
+ * the centre is good for a user interface, but too inconvenient to
+ * use internally.)
+ */
+static void do_rotate(int *grid, int w, int h, int n, int orientable,
+                      int x, int y, int dir)
+{
+    int i, j;
+
+    assert(x >= 0 && x+n <= w);
+    assert(y >= 0 && y+n <= h);
+    dir &= 3;
+    if (dir == 0)
+        return;                        /* nothing to do */
+
+    grid += y*w+x;                     /* translate region to top corner */
+
+    /*
+     * If we were leaving the result of the rotation in a separate
+     * grid, the simple thing to do would be to loop over each
+     * square within the rotated region and assign it from its
+     * source square. However, to do it in place without taking
+     * O(n^2) memory, we need to be marginally more clever. What
+     * I'm going to do is loop over about one _quarter_ of the
+     * rotated region and permute each element within that quarter
+     * with its rotational coset.
+     * 
+     * The size of the region I need to loop over is (n+1)/2 by
+     * n/2, which is an obvious exact quarter for even n and is a
+     * rectangle for odd n. (For odd n, this technique leaves out
+     * one element of the square, which is of course the central
+     * one that never moves anyway.)
+     */
+    for (i = 0; i < (n+1)/2; i++) {
+        for (j = 0; j < n/2; j++) {
+            int k;
+            int g[4];
+            int p[4];
+            
+            p[0] = j*w+i;
+            p[1] = i*w+(n-j-1);
+            p[2] = (n-j-1)*w+(n-i-1);
+            p[3] = (n-i-1)*w+j;
+
+            for (k = 0; k < 4; k++)
+                g[k] = grid[p[k]];
+
+            for (k = 0; k < 4; k++) {
+                int v = g[(k+dir) & 3];
+                if (orientable)
+                    v ^= ((v+dir) ^ v) & 3;  /* alter orientation */
+                grid[p[k]] = v;
+            }
+        }
+    }
+
+    /*
+     * Don't forget the orientation on the centre square, if n is
+     * odd.
+     */
+    if (orientable && (n & 1)) {
+        int v = grid[n/2*(w+1)];
+        v ^= ((v+dir) ^ v) & 3;  /* alter orientation */
+        grid[n/2*(w+1)] = v;
+    }
+}
+
+static int grid_complete(int *grid, int wh, int orientable)
+{
+    int ok = TRUE;
+    int i;
+    for (i = 1; i < wh; i++)
+        if (grid[i] < grid[i-1])
+            ok = FALSE;
+    if (orientable) {
+        for (i = 0; i < wh; i++)
+            if (grid[i] & 3)
+                ok = FALSE;
+    }
+    return ok;
+}
+
+static char *new_game_desc(const game_params *params, random_state *rs,
+                           char **aux, int interactive)
+{
+    int *grid;
+    int w = params->w, h = params->h, n = params->n, wh = w*h;
+    int i;
+    char *ret;
+    int retlen;
+    int total_moves;
+
+    /*
+     * Set up a solved grid.
+     */
+    grid = snewn(wh, int);
+    for (i = 0; i < wh; i++)
+        grid[i] = ((params->rowsonly ? i/w : i) + 1) * 4;
+
+    /*
+     * Shuffle it. This game is complex enough that I don't feel up
+     * to analysing its full symmetry properties (particularly at
+     * n=4 and above!), so I'm going to do it the pedestrian way
+     * and simply shuffle the grid by making a long sequence of
+     * randomly chosen moves.
+     */
+    total_moves = params->movetarget;
+    if (!total_moves)
+        /* Add a random move to avoid parity issues. */
+        total_moves = w*h*n*n*2 + random_upto(rs, 2);
+
+    do {
+        int *prevmoves;
+        int rw, rh;                    /* w/h of rotation centre space */
+
+        rw = w - n + 1;
+        rh = h - n + 1;
+        prevmoves = snewn(rw * rh, int);
+        for (i = 0; i < rw * rh; i++)
+            prevmoves[i] = 0;
+
+        for (i = 0; i < total_moves; i++) {
+            int x, y, r, oldtotal, newtotal, dx, dy;
+
+            do {
+                x = random_upto(rs, w - n + 1);
+                y = random_upto(rs, h - n + 1);
+                r = 2 * random_upto(rs, 2) - 1;
+
+                /*
+                 * See if any previous rotations has happened at
+                 * this point which nothing has overlapped since.
+                 * If so, ensure we haven't either undone a
+                 * previous move or repeated one so many times that
+                 * it turns into fewer moves in the inverse
+                 * direction (i.e. three identical rotations).
+                 */
+                oldtotal = prevmoves[y*rw+x];
+                newtotal = oldtotal + r;
+                
+                /*
+                 * Special case here for w==h==n, in which case
+                 * there is actually no way to _avoid_ all moves
+                 * repeating or undoing previous ones.
+                 */
+            } while ((w != n || h != n) &&
+                     (abs(newtotal) < abs(oldtotal) || abs(newtotal) > 2));
+
+            do_rotate(grid, w, h, n, params->orientable, x, y, r);
+
+            /*
+             * Log the rotation we've just performed at this point,
+             * for inversion detection in the next move.
+             * 
+             * Also zero a section of the prevmoves array, because
+             * any rotation area which _overlaps_ this one is now
+             * entirely safe to perform further moves in.
+             * 
+             * Two rotation areas overlap if their top left
+             * coordinates differ by strictly less than n in both
+             * directions
+             */
+            prevmoves[y*rw+x] += r;
+            for (dy = -n+1; dy <= n-1; dy++) {
+                if (y + dy < 0 || y + dy >= rh)
+                    continue;
+                for (dx = -n+1; dx <= n-1; dx++) {
+                    if (x + dx < 0 || x + dx >= rw)
+                        continue;
+                    if (dx == 0 && dy == 0)
+                        continue;
+                    prevmoves[(y+dy)*rw+(x+dx)] = 0;
+                }
+            }
+        }
+
+        sfree(prevmoves);
+
+    } while (grid_complete(grid, wh, params->orientable));
+
+    /*
+     * Now construct the game description, by describing the grid
+     * as a simple sequence of integers. They're comma-separated,
+     * unless the puzzle is orientable in which case they're
+     * separated by orientation letters `u', `d', `l' and `r'.
+     */
+    ret = NULL;
+    retlen = 0;
+    for (i = 0; i < wh; i++) {
+        char buf[80];
+        int k;
+
+        k = sprintf(buf, "%d%c", grid[i] / 4,
+                    (char)(params->orientable ? "uldr"[grid[i] & 3] : ','));
+
+        ret = sresize(ret, retlen + k + 1, char);
+        strcpy(ret + retlen, buf);
+        retlen += k;
+    }
+    if (!params->orientable)
+        ret[retlen-1] = '\0';          /* delete last comma */
+
+    sfree(grid);
+    return ret;
+}
+
+static char *validate_desc(const game_params *params, const char *desc)
+{
+    const char *p;
+    int w = params->w, h = params->h, wh = w*h;
+    int i;
+
+    p = desc;
+
+    for (i = 0; i < wh; i++) {
+        if (*p < '0' || *p > '9')
+            return "Not enough numbers in string";
+        while (*p >= '0' && *p <= '9')
+            p++;
+        if (!params->orientable && i < wh-1) {
+            if (*p != ',')
+                return "Expected comma after number";
+        } else if (params->orientable && i < wh) {
+            if (*p != 'l' && *p != 'r' && *p != 'u' && *p != 'd')
+                return "Expected orientation letter after number";
+        } else if (i == wh-1 && *p) {
+            return "Excess junk at end of string";
+        }
+
+        if (*p) p++;                   /* eat comma */
+    }
+
+    return NULL;
+}
+
+static game_state *new_game(midend *me, const game_params *params,
+                            const char *desc)
+{
+    game_state *state = snew(game_state);
+    int w = params->w, h = params->h, n = params->n, wh = w*h;
+    int i;
+    const char *p;
+
+    state->w = w;
+    state->h = h;
+    state->n = n;
+    state->orientable = params->orientable;
+    state->completed = 0;
+    state->used_solve = FALSE;
+    state->movecount = 0;
+    state->movetarget = params->movetarget;
+    state->lastx = state->lasty = state->lastr = -1;
+
+    state->grid = snewn(wh, int);
+
+    p = desc;
+
+    for (i = 0; i < wh; i++) {
+        state->grid[i] = 4 * atoi(p);
+        while (*p >= '0' && *p <= '9')
+            p++;
+        if (*p) {
+            if (params->orientable) {
+                switch (*p) {
+                  case 'l': state->grid[i] |= 1; break;
+                  case 'd': state->grid[i] |= 2; break;
+                  case 'r': state->grid[i] |= 3; break;
+                }
+            }
+            p++;
+        }
+    }
+
+    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->orientable = state->orientable;
+    ret->completed = state->completed;
+    ret->movecount = state->movecount;
+    ret->movetarget = state->movetarget;
+    ret->lastx = state->lastx;
+    ret->lasty = state->lasty;
+    ret->lastr = state->lastr;
+    ret->used_solve = state->used_solve;
+
+    ret->grid = snewn(ret->w * ret->h, int);
+    memcpy(ret->grid, state->grid, ret->w * ret->h * sizeof(int));
+
+    return ret;
+}
+
+static void free_game(game_state *state)
+{
+    sfree(state->grid);
+    sfree(state);
+}
+
+static int compare_int(const void *av, const void *bv)
+{
+    const int *a = (const int *)av;
+    const int *b = (const int *)bv;
+    if (*a < *b)
+        return -1;
+    else if (*a > *b)
+        return +1;
+    else
+        return 0;
+}
+
+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 i, x, y, col, o, maxlen;
+
+    /*
+     * First work out how many characters we need to display each
+     * number. We're pretty flexible on grid contents here, so we
+     * have to scan the entire grid.
+     */
+    col = 0;
+    for (i = 0; i < state->w * state->h; i++) {
+        x = sprintf(buf, "%d", state->grid[i] / 4);
+        if (col < x) col = x;
+    }
+    o = (state->orientable ? 1 : 0);
+
+    /*
+     * 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+o,
+     * w-1 spaces and a trailing newline.
+     */
+    maxlen = state->h * state->w * (col+o+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->grid[state->w*y+x];
+            sprintf(buf, "%*d", col, v/4);
+            memcpy(p, buf, col);
+            p += col;
+            if (o)
+                *p++ = "^<v>"[v & 3];
+            if (x+1 == state->w)
+                *p++ = '\n';
+            else
+                *p++ = ' ';
+        }
+    }
+
+    assert(p - ret == maxlen);
+    *p = '\0';
+    return ret;
+}
+
+struct game_ui {
+    int cur_x, cur_y;
+    int cur_visible;
+};
+
+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;
+
+    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 *grid;
+    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 w = state->w, h = state->h, n = state->n /* , wh = w*h */;
+    char buf[80];
+    int dir;
+
+    button = button & (~MOD_MASK | MOD_NUM_KEYPAD);
+
+    if (IS_CURSOR_MOVE(button)) {
+        if (button == CURSOR_LEFT && ui->cur_x > 0)
+            ui->cur_x--;
+        if (button == CURSOR_RIGHT && (ui->cur_x+n) < (w))
+            ui->cur_x++;
+        if (button == CURSOR_UP && ui->cur_y > 0)
+            ui->cur_y--;
+        if (button == CURSOR_DOWN && (ui->cur_y+n) < (h))
+            ui->cur_y++;
+        ui->cur_visible = 1;
+        return "";
+    }
+
+    if (button == LEFT_BUTTON || button == RIGHT_BUTTON) {
+        /*
+         * Determine the coordinates of the click. We offset by n-1
+         * half-blocks so that the user must click at the centre of
+         * a rotation region rather than at the corner.
+         */
+        x -= (n-1) * TILE_SIZE / 2;
+        y -= (n-1) * TILE_SIZE / 2;
+        x = FROMCOORD(x);
+        y = FROMCOORD(y);
+        dir = (button == LEFT_BUTTON ? 1 : -1);
+        if (x < 0 || x > w-n || y < 0 || y > h-n)
+            return NULL;
+        ui->cur_visible = 0;
+    } else if (IS_CURSOR_SELECT(button)) {
+        if (ui->cur_visible) {
+            x = ui->cur_x;
+            y = ui->cur_y;
+            dir = (button == CURSOR_SELECT2) ? -1 : +1;
+        } else {
+            ui->cur_visible = 1;
+            return "";
+        }
+    } else if (button == 'a' || button == 'A' || button==MOD_NUM_KEYPAD+'7') {
+        x = y = 0;
+        dir = (button == 'A' ? -1 : +1);
+    } else if (button == 'b' || button == 'B' || button==MOD_NUM_KEYPAD+'9') {
+        x = w-n;
+        y = 0;
+        dir = (button == 'B' ? -1 : +1);
+    } else if (button == 'c' || button == 'C' || button==MOD_NUM_KEYPAD+'1') {
+        x = 0;
+        y = h-n;
+        dir = (button == 'C' ? -1 : +1);
+    } else if (button == 'd' || button == 'D' || button==MOD_NUM_KEYPAD+'3') {
+        x = w-n;
+        y = h-n;
+        dir = (button == 'D' ? -1 : +1);
+    } else if (button==MOD_NUM_KEYPAD+'8' && (w-n) % 2 == 0) {
+        x = (w-n) / 2;
+        y = 0;
+        dir = +1;
+    } else if (button==MOD_NUM_KEYPAD+'2' && (w-n) % 2 == 0) {
+        x = (w-n) / 2;
+        y = h-n;
+        dir = +1;
+    } else if (button==MOD_NUM_KEYPAD+'4' && (h-n) % 2 == 0) {
+        x = 0;
+        y = (h-n) / 2;
+        dir = +1;
+    } else if (button==MOD_NUM_KEYPAD+'6' && (h-n) % 2 == 0) {
+        x = w-n;
+        y = (h-n) / 2;
+        dir = +1;
+    } else if (button==MOD_NUM_KEYPAD+'5' && (w-n) % 2 == 0 && (h-n) % 2 == 0){
+        x = (w-n) / 2;
+        y = (h-n) / 2;
+        dir = +1;
+    } else {
+        return NULL;                   /* no move to be made */
+    }
+
+    /*
+     * If we reach here, we have a valid move.
+     */
+    sprintf(buf, "M%d,%d,%d", x, y, dir);
+    return dupstr(buf);
+}
+
+static game_state *execute_move(const game_state *from, const 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 */
+
+    ret = dup_game(from);
+    ret->movecount++;
+    do_rotate(ret->grid, w, h, n, ret->orientable, x, y, dir);
+    ret->lastx = x;
+    ret->lasty = y;
+    ret->lastr = dir;
+
+    /*
+     * See if the game has been completed. To do this we simply
+     * test that the grid contents are in increasing order.
+     */
+    if (!ret->completed && grid_complete(ret->grid, wh, ret->orientable))
+        ret->completed = ret->movecount;
+    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);
+
+    /* cursor is light-background with a red tinge. */
+    ret[COL_HIGHCURSOR * 3 + 0] = ret[COL_BACKGROUND * 3 + 0] * 1.0F;
+    ret[COL_HIGHCURSOR * 3 + 1] = ret[COL_BACKGROUND * 3 + 1] * 0.5F;
+    ret[COL_HIGHCURSOR * 3 + 2] = ret[COL_BACKGROUND * 3 + 2] * 0.5F;
+
+    for (i = 0; i < 3; i++) {
+        ret[COL_HIGHLIGHT_GENTLE * 3 + i] = ret[COL_BACKGROUND * 3 + i] * 1.1F;
+        ret[COL_LOWLIGHT_GENTLE * 3 + i] = ret[COL_BACKGROUND * 3 + i] * 0.9F;
+        ret[COL_TEXT * 3 + i] = 0.0;
+        ret[COL_LOWCURSOR * 3 + i] = ret[COL_HIGHCURSOR * 3 + i] * 0.6F;
+    }
+
+    *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->grid = snewn(ds->w*ds->h, int);
+    ds->tilesize = 0;                  /* haven't decided yet */
+    for (i = 0; i < ds->w*ds->h; i++)
+        ds->grid[i] = -1;
+    ds->cur_x = ds->cur_y = -state->n;
+
+    return ds;
+}
+
+static void game_free_drawstate(drawing *dr, game_drawstate *ds)
+{
+    sfree(ds->grid);
+    sfree(ds);
+}
+
+struct rotation {
+    int cx, cy, cw, ch;                /* clip region */
+    int ox, oy;                        /* rotation origin */
+    float c, s;                        /* cos and sin of rotation angle */
+    int lc, rc, tc, bc;                /* colours of tile edges */
+};
+
+static void rotate(int *xy, struct rotation *rot)
+{
+    if (rot) {
+        float xf = (float)xy[0] - rot->ox, yf = (float)xy[1] - rot->oy;
+        float xf2, yf2;
+
+        xf2 = rot->c * xf + rot->s * yf;
+        yf2 = - rot->s * xf + rot->c * yf;
+
+        xy[0] = (int)(xf2 + rot->ox + 0.5);   /* round to nearest */
+        xy[1] = (int)(yf2 + rot->oy + 0.5);   /* round to nearest */
+    }
+}
+
+#define CUR_TOP         1
+#define CUR_RIGHT       2
+#define CUR_BOTTOM      4
+#define CUR_LEFT        8
+
+static void draw_tile(drawing *dr, game_drawstate *ds, const game_state *state,
+                      int x, int y, int tile, int flash_colour,
+                      struct rotation *rot, unsigned cedges)
+{
+    int coords[8];
+    char str[40];
+
+    /*
+     * If we've been passed a rotation region but we're drawing a
+     * tile which is outside it, we must draw it normally. This can
+     * occur if we're cleaning up after a completion flash while a
+     * new move is also being made.
+     */
+    if (rot && (x < rot->cx || y < rot->cy ||
+                x >= rot->cx+rot->cw || y >= rot->cy+rot->ch))
+        rot = NULL;
+
+    if (rot)
+        clip(dr, rot->cx, rot->cy, rot->cw, rot->ch);
+
+    /*
+     * We must draw each side of the tile's highlight separately,
+     * because in some cases (during rotation) they will all need
+     * to be different colours.
+     */
+
+    /* The centre point is common to all sides. */
+    coords[4] = x + TILE_SIZE / 2;
+    coords[5] = y + TILE_SIZE / 2;
+    rotate(coords+4, rot);
+
+    /* Right side. */
+    coords[0] = x + TILE_SIZE - 1;
+    coords[1] = y + TILE_SIZE - 1;
+    rotate(coords+0, rot);
+    coords[2] = x + TILE_SIZE - 1;
+    coords[3] = y;
+    rotate(coords+2, rot);
+    draw_polygon(dr, coords, 3, rot ? rot->rc : COL_LOWLIGHT,
+                 rot ? rot->rc : (cedges & CUR_RIGHT) ? COL_LOWCURSOR : COL_LOWLIGHT);
+
+    /* Bottom side. */
+    coords[2] = x;
+    coords[3] = y + TILE_SIZE - 1;
+    rotate(coords+2, rot);
+    draw_polygon(dr, coords, 3, rot ? rot->bc : COL_LOWLIGHT,
+                 rot ? rot->bc : (cedges & CUR_BOTTOM) ? COL_LOWCURSOR : COL_LOWLIGHT);
+
+    /* Left side. */
+    coords[0] = x;
+    coords[1] = y;
+    rotate(coords+0, rot);
+    draw_polygon(dr, coords, 3, rot ? rot->lc : COL_HIGHLIGHT,
+                 rot ? rot->lc : (cedges & CUR_LEFT) ? COL_HIGHCURSOR : COL_HIGHLIGHT);
+
+    /* Top side. */
+    coords[2] = x + TILE_SIZE - 1;
+    coords[3] = y;
+    rotate(coords+2, rot);
+    draw_polygon(dr, coords, 3, rot ? rot->tc : COL_HIGHLIGHT,
+                 rot ? rot->tc : (cedges & CUR_TOP) ? COL_HIGHCURSOR : COL_HIGHLIGHT);
+
+    /*
+     * Now the main blank area in the centre of the tile.
+     */
+    if (rot) {
+        coords[0] = x + HIGHLIGHT_WIDTH;
+        coords[1] = y + HIGHLIGHT_WIDTH;
+        rotate(coords+0, rot);
+        coords[2] = x + HIGHLIGHT_WIDTH;
+        coords[3] = y + TILE_SIZE - 1 - HIGHLIGHT_WIDTH;
+        rotate(coords+2, rot);
+        coords[4] = x + TILE_SIZE - 1 - HIGHLIGHT_WIDTH;
+        coords[5] = y + TILE_SIZE - 1 - HIGHLIGHT_WIDTH;
+        rotate(coords+4, rot);
+        coords[6] = x + TILE_SIZE - 1 - HIGHLIGHT_WIDTH;
+        coords[7] = y + HIGHLIGHT_WIDTH;
+        rotate(coords+6, rot);
+        draw_polygon(dr, coords, 4, flash_colour, flash_colour);
+    } else {
+        draw_rect(dr, x + HIGHLIGHT_WIDTH, y + HIGHLIGHT_WIDTH,
+                  TILE_SIZE - 2*HIGHLIGHT_WIDTH, TILE_SIZE - 2*HIGHLIGHT_WIDTH,
+                  flash_colour);
+    }
+
+    /*
+     * Next, the triangles for orientation.
+     */
+    if (state->orientable) {
+        int xdx, xdy, ydx, ydy;
+        int cx, cy, displ, displ2;
+        switch (tile & 3) {
+          case 0:
+            xdx = 1, xdy = 0;
+            ydx = 0, ydy = 1;
+            break;
+          case 1:
+            xdx = 0, xdy = -1;
+            ydx = 1, ydy = 0;
+            break;
+          case 2:
+            xdx = -1, xdy = 0;
+            ydx = 0, ydy = -1;
+            break;
+          default /* case 3 */:
+            xdx = 0, xdy = 1;
+            ydx = -1, ydy = 0;
+            break;
+        }
+
+        cx = x + TILE_SIZE / 2;
+        cy = y + TILE_SIZE / 2;
+        displ = TILE_SIZE / 2 - HIGHLIGHT_WIDTH - 2;
+        displ2 = TILE_SIZE / 3 - HIGHLIGHT_WIDTH;
+
+        coords[0] = cx - displ * xdx + displ2 * ydx;
+        coords[1] = cy - displ * xdy + displ2 * ydy;
+        rotate(coords+0, rot);
+        coords[2] = cx + displ * xdx + displ2 * ydx;
+        coords[3] = cy + displ * xdy + displ2 * ydy;
+        rotate(coords+2, rot);
+        coords[4] = cx - displ * ydx;
+        coords[5] = cy - displ * ydy;
+        rotate(coords+4, rot);
+        draw_polygon(dr, coords, 3, COL_LOWLIGHT_GENTLE, COL_LOWLIGHT_GENTLE);
+    }
+
+    coords[0] = x + TILE_SIZE/2;
+    coords[1] = y + TILE_SIZE/2;
+    rotate(coords+0, rot);
+    sprintf(str, "%d", tile / 4);
+    draw_text(dr, coords[0], coords[1],
+              FONT_VARIABLE, TILE_SIZE/3, ALIGN_VCENTRE | ALIGN_HCENTRE,
+              COL_TEXT, str);
+
+    if (rot)
+        unclip(dr);
+
+    draw_update(dr, x, y, TILE_SIZE, TILE_SIZE);
+}
+
+static int highlight_colour(float angle)
+{
+    int colours[32] = {
+        COL_LOWLIGHT,
+        COL_LOWLIGHT_GENTLE,
+        COL_LOWLIGHT_GENTLE,
+        COL_LOWLIGHT_GENTLE,
+        COL_HIGHLIGHT_GENTLE,
+        COL_HIGHLIGHT_GENTLE,
+        COL_HIGHLIGHT_GENTLE,
+        COL_HIGHLIGHT,
+        COL_HIGHLIGHT,
+        COL_HIGHLIGHT,
+        COL_HIGHLIGHT,
+        COL_HIGHLIGHT,
+        COL_HIGHLIGHT,
+        COL_HIGHLIGHT,
+        COL_HIGHLIGHT,
+        COL_HIGHLIGHT,
+        COL_HIGHLIGHT,
+        COL_HIGHLIGHT_GENTLE,
+        COL_HIGHLIGHT_GENTLE,
+        COL_HIGHLIGHT_GENTLE,
+        COL_LOWLIGHT_GENTLE,
+        COL_LOWLIGHT_GENTLE,
+        COL_LOWLIGHT_GENTLE,
+        COL_LOWLIGHT,
+        COL_LOWLIGHT,
+        COL_LOWLIGHT,
+        COL_LOWLIGHT,
+        COL_LOWLIGHT,
+        COL_LOWLIGHT,
+        COL_LOWLIGHT,
+        COL_LOWLIGHT,
+        COL_LOWLIGHT,
+    };
+
+    return colours[(int)((angle + 2*PI) / (PI/16)) & 31];
+}
+
+static float game_anim_length_real(const game_state *oldstate,
+                                   const game_state *newstate, int dir,
+                                   const game_ui *ui)
+{
+    /*
+     * Our game_anim_length doesn't need to modify its game_ui, so
+     * this is the real function which declares ui as const. We must
+     * wrap this for the backend structure with a version that has ui
+     * non-const, but we still need this version to call from within
+     * game_redraw which only has a const ui available.
+     */
+    return (float)(ANIM_PER_BLKSIZE_UNIT * sqrt(newstate->n-1));
+}
+
+static float game_anim_length(const game_state *oldstate,
+                              const game_state *newstate, int dir, game_ui *ui)
+{
+    return game_anim_length_real(oldstate, newstate, dir, ui);
+
+}
+
+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 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;
+    struct rotation srot, *rot;
+    int lastx = -1, lasty = -1, lastr = -1;
+    int cx, cy, cmoved = 0, n = state->n;
+
+    cx = ui->cur_visible ? ui->cur_x : -state->n;
+    cy = ui->cur_visible ? ui->cur_y : -state->n;
+    if (cx != ds->cur_x || cy != ds->cur_y)
+        cmoved = 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);
+
+        ds->started = TRUE;
+    }
+
+    /*
+     * If we're drawing any rotated tiles, sort out the rotation
+     * parameters, and also zap the rotation region to the
+     * background colour before doing anything else.
+     */
+    if (oldstate) {
+        float angle;
+        float anim_max = game_anim_length_real(oldstate, state, dir, ui);
+
+        if (dir > 0) {
+            lastx = state->lastx;
+            lasty = state->lasty;
+            lastr = state->lastr;
+        } else {
+            lastx = oldstate->lastx;
+            lasty = oldstate->lasty;
+            lastr = -oldstate->lastr;
+        }
+
+        rot = &srot;
+        rot->cx = COORD(lastx);
+        rot->cy = COORD(lasty);
+        rot->cw = rot->ch = TILE_SIZE * state->n;
+        rot->ox = rot->cx + rot->cw/2;
+        rot->oy = rot->cy + rot->ch/2;
+        angle = (float)((-PI/2 * lastr) * (1.0 - animtime / anim_max));
+        rot->c = (float)cos(angle);
+        rot->s = (float)sin(angle);
+
+        /*
+         * Sort out the colours of the various sides of the tile.
+         */
+        rot->lc = highlight_colour((float)PI + angle);
+        rot->rc = highlight_colour(angle);
+        rot->tc = highlight_colour((float)(PI/2.0) + angle);
+        rot->bc = highlight_colour((float)(-PI/2.0) + angle);
+
+        draw_rect(dr, rot->cx, rot->cy, rot->cw, rot->ch, bgcolour);
+    } else
+        rot = NULL;
+
+    /*
+     * Now draw each tile.
+     */
+    for (i = 0; i < state->w * state->h; i++) {
+        int t, cc = 0;
+        int tx = i % state->w, ty = i / state->w;
+
+        /*
+         * Figure out what should be displayed at this location.
+         * Usually it will be state->grid[i], unless we're in the
+         * middle of animating an actual rotation and this cell is
+         * within the rotation region, in which case we set -1
+         * (always display).
+         */
+        if (oldstate && lastx >= 0 && lasty >= 0 &&
+            tx >= lastx && tx < lastx + state->n &&
+            ty >= lasty && ty < lasty + state->n)
+            t = -1;
+        else
+            t = state->grid[i];
+
+        if (cmoved) {
+            /* cursor has moved (or changed visibility)... */
+            if (tx == cx || tx == cx+n-1 || ty == cy || ty == cy+n-1)
+                cc = 1; /* ...we're on new cursor, redraw */
+            if (tx == ds->cur_x || tx == ds->cur_x+n-1 ||
+                ty == ds->cur_y || ty == ds->cur_y+n-1)
+                cc = 1; /* ...we were on old cursor, redraw */
+        }
+
+        if (ds->bgcolour != bgcolour ||   /* always redraw when flashing */
+            ds->grid[i] != t || ds->grid[i] == -1 || t == -1 || cc) {
+            int x = COORD(tx), y = COORD(ty);
+            unsigned cedges = 0;
+
+            if (tx == cx     && ty >= cy && ty <= cy+n-1) cedges |= CUR_LEFT;
+            if (ty == cy     && tx >= cx && tx <= cx+n-1) cedges |= CUR_TOP;
+            if (tx == cx+n-1 && ty >= cy && ty <= cy+n-1) cedges |= CUR_RIGHT;
+            if (ty == cy+n-1 && tx >= cx && tx <= cx+n-1) cedges |= CUR_BOTTOM;
+
+            draw_tile(dr, ds, state, x, y, state->grid[i], bgcolour, rot, cedges);
+            ds->grid[i] = t;
+        }
+    }
+    ds->bgcolour = bgcolour;
+    ds->cur_x = cx; ds->cur_y = cy;
+
+    /*
+     * 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 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 twiddle
+#endif
+
+const struct game thegame = {
+    "Twiddle", "games.twiddle", "twiddle",
+    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: */