chiark / gitweb /
Tents: mark squares as non-tents with {Shift,Control}-cursor keys.
[sgt-puzzles.git] / guess.c
diff --git a/guess.c b/guess.c
index 6d96ea3754cf7f46ab224fe61b49e4ec2738a6d9..df9b7f628c9d117d614257d93b3f44794b20fed5 100644 (file)
--- a/guess.c
+++ b/guess.c
@@ -15,7 +15,7 @@
 
 enum {
     COL_BACKGROUND,
-    COL_HIGHLIGHT, COL_LOWLIGHT, COL_FRAME, COL_FLASH, COL_HOLD,
+    COL_FRAME, COL_CURSOR, COL_FLASH, COL_HOLD,
     COL_EMPTY, /* must be COL_1 - 1 */
     COL_1, COL_2, COL_3, COL_4, COL_5, COL_6, COL_7, COL_8, COL_9, COL_10,
     COL_CORRECTPLACE, COL_CORRECTCOLOUR,
@@ -24,6 +24,7 @@ enum {
 
 struct game_params {
     int ncolours, npegs, nguesses;
+    int allow_blank, allow_multiple;
 };
 
 #define FEEDBACK_CORRECTPLACE  1
@@ -38,10 +39,11 @@ typedef struct pegrow {
 struct game_state {
     game_params params;
     pegrow *guesses;  /* length params->nguesses */
+    int *holds;
     pegrow solution;
     int next_go; /* from 0 to nguesses-1;
                     if next_go == nguesses then they've lost. */
-    int solved;
+    int solved;   /* +1 = win, -1 = lose, 0 = still playing */
 };
 
 static game_params *default_params(void)
@@ -53,12 +55,10 @@ static game_params *default_params(void)
     ret->npegs = 4;
     ret->nguesses = 10;
 
-    return ret;
-}
+    ret->allow_blank = 0;
+    ret->allow_multiple = 1;
 
-static int game_fetch_preset(int i, char **name, game_params **params)
-{
-    return FALSE;
+    return ret;
 }
 
 static void free_params(game_params *params)
@@ -66,13 +66,39 @@ static void free_params(game_params *params)
     sfree(params);
 }
 
-static game_params *dup_params(game_params *params)
+static game_params *dup_params(const game_params *params)
 {
     game_params *ret = snew(game_params);
     *ret = *params;                   /* structure copy */
     return ret;
 }
 
+static const struct {
+    char *name;
+    game_params params;
+} guess_presets[] = {
+    {"Standard", {6, 4, 10, FALSE, TRUE}},
+    {"Super", {8, 5, 12, FALSE, TRUE}},
+};
+
+
+static int game_fetch_preset(int i, char **name, game_params **params)
+{
+    if (i < 0 || i >= lenof(guess_presets))
+        return FALSE;
+
+    *name = dupstr(guess_presets[i].name);
+    /*
+     * get round annoying const issues
+     */
+    {
+        game_params tmp = guess_presets[i].params;
+        *params = dup_params(&tmp);
+    }
+
+    return TRUE;
+}
+
 static void decode_params(game_params *params, char const *string)
 {
     char const *p = string;
@@ -97,55 +123,83 @@ static void decode_params(game_params *params, char const *string)
            while (*p && isdigit((unsigned char)*p)) p++;
            break;
 
+        case 'b':
+            params->allow_blank = 1;
+            break;
+
+        case 'B':
+            params->allow_blank = 0;
+            break;
+
+        case 'm':
+            params->allow_multiple = 1;
+            break;
+
+        case 'M':
+            params->allow_multiple = 0;
+            break;
+
        default:
             ;
        }
     }
 }
 
-static char *encode_params(game_params *params, int full)
+static char *encode_params(const game_params *params, int full)
 {
     char data[256];
 
-    sprintf(data, "c%dp%dg%d", params->ncolours, params->npegs, params->nguesses);
+    sprintf(data, "c%dp%dg%d%s%s",
+            params->ncolours, params->npegs, params->nguesses,
+            params->allow_blank ? "b" : "B", params->allow_multiple ? "m" : "M");
 
     return dupstr(data);
 }
 
-static config_item *game_configure(game_params *params)
+static config_item *game_configure(const game_params *params)
 {
     config_item *ret;
     char buf[80];
 
-    ret = snewn(4, config_item);
+    ret = snewn(6, config_item);
 
-    ret[0].name = "No. of colours";
+    ret[0].name = "Colours";
     ret[0].type = C_STRING;
     sprintf(buf, "%d", params->ncolours);
     ret[0].sval = dupstr(buf);
     ret[0].ival = 0;
 
-    ret[1].name = "No. of pegs per row";
+    ret[1].name = "Pegs per guess";
     ret[1].type = C_STRING;
     sprintf(buf, "%d", params->npegs);
     ret[1].sval = dupstr(buf);
     ret[1].ival = 0;
 
-    ret[2].name = "No. of guesses";
+    ret[2].name = "Guesses";
     ret[2].type = C_STRING;
     sprintf(buf, "%d", params->nguesses);
     ret[2].sval = dupstr(buf);
     ret[2].ival = 0;
 
-    ret[3].name = NULL;
-    ret[3].type = C_END;
+    ret[3].name = "Allow blanks";
+    ret[3].type = C_BOOLEAN;
     ret[3].sval = NULL;
-    ret[3].ival = 0;
+    ret[3].ival = params->allow_blank;
+
+    ret[4].name = "Allow duplicates";
+    ret[4].type = C_BOOLEAN;
+    ret[4].sval = NULL;
+    ret[4].ival = params->allow_multiple;
+
+    ret[5].name = NULL;
+    ret[5].type = C_END;
+    ret[5].sval = NULL;
+    ret[5].ival = 0;
 
     return ret;
 }
 
-static game_params *custom_params(config_item *cfg)
+static game_params *custom_params(const config_item *cfg)
 {
     game_params *ret = snew(game_params);
 
@@ -153,10 +207,13 @@ static game_params *custom_params(config_item *cfg)
     ret->npegs = atoi(cfg[1].sval);
     ret->nguesses = atoi(cfg[2].sval);
 
+    ret->allow_blank = cfg[3].ival;
+    ret->allow_multiple = cfg[4].ival;
+
     return ret;
 }
 
-static char *validate_params(game_params *params)
+static char *validate_params(const game_params *params, int full)
 {
     if (params->ncolours < 2 || params->npegs < 2)
        return "Trivial solutions are uninteresting";
@@ -166,6 +223,8 @@ static char *validate_params(game_params *params)
        return "Too many colours";
     if (params->nguesses < 1)
        return "Must have at least one guess";
+    if (!params->allow_multiple && params->ncolours < params->npegs)
+        return "Disallowing multiple colours requires at least as many colours as pegs";
     return NULL;
 }
 
@@ -184,12 +243,9 @@ static pegrow new_pegrow(int npegs)
 
 static pegrow dup_pegrow(pegrow pegs)
 {
-    pegrow newpegs = snew(struct pegrow);
+    pegrow newpegs = new_pegrow(pegs->npegs);
 
-    newpegs->npegs = pegs->npegs;
-    newpegs->pegs = snewn(newpegs->npegs, int);
     memcpy(newpegs->pegs, pegs->pegs, newpegs->npegs * sizeof(int));
-    newpegs->feedback = snewn(newpegs->npegs, int);
     memcpy(newpegs->feedback, pegs->feedback, newpegs->npegs * sizeof(int));
 
     return newpegs;
@@ -208,37 +264,54 @@ static void free_pegrow(pegrow pegs)
     sfree(pegs);
 }
 
-static char *new_game_desc(game_params *params, random_state *rs,
-                          game_aux_info **aux, int interactive)
+static char *new_game_desc(const game_params *params, random_state *rs,
+                          char **aux, int interactive)
 {
     unsigned char *bmp = snewn(params->npegs, unsigned char);
     char *ret;
-    int i;
-
-    for (i = 0; i < params->npegs; i++)
-        bmp[i] = (unsigned char)(random_upto(rs, params->ncolours)+1);
+    int i, c;
+    pegrow colcount = new_pegrow(params->ncolours);
+
+    for (i = 0; i < params->npegs; i++) {
+newcol:
+        c = random_upto(rs, params->ncolours);
+        if (!params->allow_multiple && colcount->pegs[c]) goto newcol;
+        colcount->pegs[c]++;
+        bmp[i] = (unsigned char)(c+1);
+    }
     obfuscate_bitmap(bmp, params->npegs*8, FALSE);
 
     ret = bin2hex(bmp, params->npegs);
     sfree(bmp);
+    free_pegrow(colcount);
     return ret;
 }
 
-static void game_free_aux_info(game_aux_info *aux)
+static char *validate_desc(const game_params *params, const char *desc)
 {
-    assert(!"Shouldn't happen");
-}
+    unsigned char *bmp;
+    int i;
 
-static char *validate_desc(game_params *params, char *desc)
-{
-    /* desc is just an (obfuscated) bitmap of the solution; all we
-     * care is that it's the correct length. */
+    /* desc is just an (obfuscated) bitmap of the solution; check that
+     * it's the correct length and (when unobfuscated) contains only
+     * sensible colours. */
     if (strlen(desc) != params->npegs * 2)
         return "Game description is wrong length";
+    bmp = hex2bin(desc, params->npegs);
+    obfuscate_bitmap(bmp, params->npegs*8, TRUE);
+    for (i = 0; i < params->npegs; i++) {
+        if (bmp[i] < 1 || bmp[i] > params->ncolours) {
+            sfree(bmp);
+            return "Game description is corrupted";
+        }
+    }
+    sfree(bmp);
+
     return NULL;
 }
 
-static game_state *new_game(midend_data *me, game_params *params, char *desc)
+static game_state *new_game(midend *me, const game_params *params,
+                            const char *desc)
 {
     game_state *state = snew(game_state);
     unsigned char *bmp;
@@ -248,6 +321,7 @@ static game_state *new_game(midend_data *me, game_params *params, char *desc)
     state->guesses = snewn(params->nguesses, pegrow);
     for (i = 0; i < params->nguesses; i++)
        state->guesses[i] = new_pegrow(params->npegs);
+    state->holds = snewn(params->npegs, int);
     state->solution = new_pegrow(params->npegs);
 
     bmp = hex2bin(desc, params->npegs);
@@ -256,20 +330,24 @@ static game_state *new_game(midend_data *me, game_params *params, char *desc)
        state->solution->pegs[i] = (int)bmp[i];
     sfree(bmp);
 
+    memset(state->holds, 0, sizeof(int) * params->npegs);
     state->next_go = state->solved = 0;
 
     return state;
 }
 
-static game_state *dup_game(game_state *state)
+static game_state *dup_game(const game_state *state)
 {
     game_state *ret = snew(game_state);
     int i;
 
     *ret = *state;
+
     ret->guesses = snewn(state->params.nguesses, pegrow);
     for (i = 0; i < state->params.nguesses; i++)
        ret->guesses[i] = dup_pegrow(state->guesses[i]);
+    ret->holds = snewn(state->params.npegs, int);
+    memcpy(ret->holds, state->holds, sizeof(int) * state->params.npegs);
     ret->solution = dup_pegrow(state->solution);
 
     return ret;
@@ -282,25 +360,57 @@ static void free_game(game_state *state)
     free_pegrow(state->solution);
     for (i = 0; i < state->params.nguesses; i++)
        free_pegrow(state->guesses[i]);
+    sfree(state->holds);
     sfree(state->guesses);
 
     sfree(state);
 }
 
-static game_state *solve_game(game_state *state, game_state *currstate,
-                              game_aux_info *aux, char **error)
+static char *solve_game(const game_state *state, const game_state *currstate,
+                        const char *aux, char **error)
 {
-    game_state *ret = dup_game(currstate);
-    ret->solved = 1;
-    return ret;
+    return dupstr("S");
 }
 
-static char *game_text_format(game_state *state)
+static int game_can_format_as_text_now(const game_params *params)
+{
+    return TRUE;
+}
+
+static char *game_text_format(const game_state *state)
 {
     return NULL;
 }
 
+static int is_markable(const game_params *params, pegrow pegs)
+{
+    int i, nset = 0, nrequired, ret = 0;
+    pegrow colcount = new_pegrow(params->ncolours);
+
+    nrequired = params->allow_blank ? 1 : params->npegs;
+
+    for (i = 0; i < params->npegs; i++) {
+        int c = pegs->pegs[i];
+        if (c > 0) {
+            colcount->pegs[c-1]++;
+            nset++;
+        }
+    }
+    if (nset < nrequired) goto done;
+
+    if (!params->allow_multiple) {
+        for (i = 0; i < params->ncolours; i++) {
+            if (colcount->pegs[i] > 1) goto done;
+        }
+    }
+    ret = 1;
+done:
+    free_pegrow(colcount);
+    return ret;
+}
+
 struct game_ui {
+    game_params params;
     pegrow curr_pegs; /* half-finished current move */
     int *holds;
     int colour_cur;   /* position of up-down colour picker cursor */
@@ -308,33 +418,101 @@ struct game_ui {
     int display_cur, markable;
 
     int drag_col, drag_x, drag_y; /* x and y are *center* of peg! */
+    int drag_opeg; /* peg index, if dragged from a peg (from current guess), otherwise -1 */
+
+    int show_labels;                   /* label the colours with letters */
+    pegrow hint;
 };
 
-static game_ui *new_ui(game_state *state)
+static game_ui *new_ui(const game_state *state)
 {
-    game_ui *ui = snew(struct game_ui);
-    memset(ui, 0, sizeof(struct game_ui));
+    game_ui *ui = snew(game_ui);
+    memset(ui, 0, sizeof(game_ui));
+    ui->params = state->params;        /* structure copy */
     ui->curr_pegs = new_pegrow(state->params.npegs);
     ui->holds = snewn(state->params.npegs, int);
     memset(ui->holds, 0, sizeof(int)*state->params.npegs);
+    ui->drag_opeg = -1;
     return ui;
 }
 
 static void free_ui(game_ui *ui)
 {
+    if (ui->hint)
+        free_pegrow(ui->hint);
     free_pegrow(ui->curr_pegs);
     sfree(ui->holds);
     sfree(ui);
 }
 
-static void game_changed_state(game_ui *ui, game_state *oldstate,
-                               game_state *newstate)
+static char *encode_ui(const game_ui *ui)
+{
+    char *ret, *p, *sep;
+    int i;
+
+    /*
+     * For this game it's worth storing the contents of the current
+     * guess, and the current set of holds.
+     */
+    ret = snewn(40 * ui->curr_pegs->npegs, char);
+    p = ret;
+    sep = "";
+    for (i = 0; i < ui->curr_pegs->npegs; i++) {
+        p += sprintf(p, "%s%d%s", sep, ui->curr_pegs->pegs[i],
+                     ui->holds[i] ? "_" : "");
+        sep = ",";
+    }
+    *p++ = '\0';
+    assert(p - ret < 40 * ui->curr_pegs->npegs);
+    return sresize(ret, p - ret, char);
+}
+
+static void decode_ui(game_ui *ui, const char *encoding)
+{
+    int i;
+    const char *p = encoding;
+    for (i = 0; i < ui->curr_pegs->npegs; i++) {
+        ui->curr_pegs->pegs[i] = atoi(p);
+        while (*p && isdigit((unsigned char)*p)) p++;
+        if (*p == '_') {
+            /* NB: old versions didn't store holds */
+            ui->holds[i] = 1;
+            p++;
+        } else
+            ui->holds[i] = 0;
+        if (*p == ',') p++;
+    }
+    ui->markable = is_markable(&ui->params, ui->curr_pegs);
+}
+
+static void game_changed_state(game_ui *ui, const game_state *oldstate,
+                               const game_state *newstate)
 {
     int i;
 
-    /* just clear the row-in-progress when we have an undo/redo. */
-    for (i = 0; i < ui->curr_pegs->npegs; i++)
-       ui->curr_pegs->pegs[i] = 0;
+    if (newstate->next_go < oldstate->next_go) {
+        sfree(ui->hint);
+        ui->hint = NULL;
+    }
+
+    /* Implement holds, clear other pegs.
+     * This does something that is arguably the Right Thing even
+     * for undo. */
+    for (i = 0; i < newstate->solution->npegs; i++) {
+        if (newstate->solved)
+            ui->holds[i] = 0;
+        else
+            ui->holds[i] = newstate->holds[i];
+       if (newstate->solved || (newstate->next_go == 0) || !ui->holds[i]) {
+           ui->curr_pegs->pegs[i] = 0;
+       } else
+            ui->curr_pegs->pegs[i] =
+                newstate->guesses[newstate->next_go-1]->pegs[i];
+    }
+    ui->markable = is_markable(&newstate->params, ui->curr_pegs);
+    /* Clean up cursor position */
+    if (!ui->markable && ui->peg_cur == newstate->solution->npegs)
+       ui->peg_cur--;
 }
 
 #define PEGSZ   (ds->pegsz)
@@ -342,6 +520,9 @@ static void game_changed_state(game_ui *ui, game_state *oldstate,
 #define HINTSZ  (ds->hintsz)
 #define HINTOFF (ds->hintsz + ds->gapsz)
 
+#define GAP     (ds->gapsz)
+#define CGAP    (ds->gapsz / 2)
+
 #define PEGRAD  (ds->pegrad)
 #define HINTRAD (ds->hintrad)
 
@@ -363,7 +544,7 @@ static void game_changed_state(game_ui *ui, game_state *oldstate,
 #define HINT_OY         (GUESS_OY + (PEGSZ - HINTOFF - HINTSZ) / 2)
 #define HINT_X(g)       HINT_OX
 #define HINT_Y(g)       (HINT_OY + (g)*PEGOFF)
-#define HINT_W          (ds->hintw*HINTOFF)
+#define HINT_W          ((ds->hintw*HINTOFF) - GAP)
 #define HINT_H          GUESS_H
 
 #define SOLN_OX         GUESS_OX
@@ -377,8 +558,6 @@ struct game_drawstate {
     pegrow solution;    /* only displayed if state->solved */
     pegrow colours;     /* length ncolours, not npegs */
 
-    int *holds;
-
     int pegsz, hintsz, gapsz; /* peg size (diameter), etc. */
     int pegrad, hintrad;      /* radius of peg, hint */
     int border;
@@ -388,28 +567,19 @@ struct game_drawstate {
     int hintw;          /* no. of hint tiles we're wide per row */
     int w, h, started, solved;
 
-    int colour_cur, peg_cur, display_cur; /* as in game_ui. */
     int next_go;
 
     blitter *blit_peg;
     int drag_col, blit_ox, blit_oy;
 };
 
-static void set_peg(game_ui *ui, int peg, int col)
+static void set_peg(const game_params *params, game_ui *ui, int peg, int col)
 {
-    int i;
-
     ui->curr_pegs->pegs[peg] = col;
-
-    /* set to 'markable' if all of our pegs are filled. */
-    for (i = 0; i < ui->curr_pegs->npegs; i++) {
-        if (ui->curr_pegs->pegs[i] == 0) return;
-    }
-    debug(("UI is markable."));
-    ui->markable = 1;
+    ui->markable = is_markable(params, ui->curr_pegs);
 }
 
-static int mark_pegs(pegrow guess, pegrow solution, int ncols)
+static int mark_pegs(pegrow guess, const pegrow solution, int ncols)
 {
     int nc_place = 0, nc_colour = 0, i, j;
 
@@ -449,66 +619,193 @@ static int mark_pegs(pegrow guess, pegrow solution, int ncols)
     return nc_place;
 }
 
-static game_state *mark_move(game_state *from, game_ui *ui)
+static char *encode_move(const game_state *from, game_ui *ui)
 {
-    int i, ncleared = 0, nc_place;
-    game_state *to = dup_game(from);
+    char *buf, *p, *sep;
+    int len, i;
+
+    len = ui->curr_pegs->npegs * 20 + 2;
+    buf = snewn(len, char);
+    p = buf;
+    *p++ = 'G';
+    sep = "";
+    for (i = 0; i < ui->curr_pegs->npegs; i++) {
+       p += sprintf(p, "%s%d%s", sep, ui->curr_pegs->pegs[i],
+                     ui->holds[i] ? "_" : "");
+       sep = ",";
+    }
+    *p++ = '\0';
+    assert(p - buf <= len);
+    buf = sresize(buf, len, char);
+
+    return buf;
+}
 
-    for (i = 0; i < to->solution->npegs; i++) {
-        to->guesses[from->next_go]->pegs[i] = ui->curr_pegs->pegs[i];
+static void compute_hint(const game_state *state, game_ui *ui)
+{
+    /* Suggest the lexicographically first row consistent with all
+     * previous feedback.  This is not only a useful hint, but also
+     * a reasonable strategy if applied consistently.  If the user
+     * uses hints in every turn, they may be able to intuit this
+     * strategy, or one similar to it.  I (Jonas Kölker) came up
+     * with something close to it without seeing it in action. */
+
+    /* Some performance characteristics: I want to ask for each n,
+     * how many solutions are guessed in exactly n guesses if you
+     * use the hint in each turn.
+     *
+     * With 4 pegs and 6 colours you get the following histogram:
+     *
+     *  1 guesses:     1 solution
+     *  2 guesses:     4 solutions
+     *  3 guesses:    25 solutions
+     *  4 guesses:   108 solutions
+     *  5 guesses:   305 solutions
+     *  6 guesses:   602 solutions
+     *  7 guesses:   196 solutions
+     *  8 guesses:    49 solutions
+     *  9 guesses:     6 solutions
+     * (note: the tenth guess is never necessary.)
+     *
+     * With 5 pegs and 8 colours you get the following histogram:
+     *
+     *  1 guesses:     1 solution
+     *  2 guesses:     5 solutions
+     *  3 guesses:    43 solutions
+     *  4 guesses:   278 solutions
+     *  5 guesses:  1240 solutions
+     *  6 guesses:  3515 solutions
+     *  7 guesses:  7564 solutions
+     *  8 guesses: 14086 solutions
+     *  9 guesses:  4614 solutions
+     * 10 guesses:  1239 solutions
+     * 11 guesses:   175 solutions
+     * 12 guesses:     7 solutions
+     * 13 guesses:     1 solution
+     *
+     * The solution which takes too many guesses is {8, 8, 5, 6, 7}.
+     * The game ID is c8p5g12Bm:4991e5e41a. */
+
+    int mincolour = 1, maxcolour = 0, i, j;
+
+    /* For large values of npegs and ncolours, the lexicographically
+     * next guess make take a while to find.  Finding upper and
+     * lower limits on which colours we have to consider will speed
+     * this up, as will caching our progress from one invocation to
+     * the next.  The latter strategy works, since if we have ruled
+     * out a candidate we will never reverse this judgment in the
+     * light of new information.  Removing information, i.e. undo,
+     * will require us to backtrack somehow.  We backtrack by fully
+     * forgetting our progress (and recomputing it if required). */
+
+    for (i = 0; i < state->next_go; ++i)
+        for (j = 0; j < state->params.npegs; ++j)
+            if (state->guesses[i]->pegs[j] > maxcolour)
+                maxcolour = state->guesses[i]->pegs[j];
+    maxcolour = min(maxcolour + 1, state->params.ncolours);
+
+increase_mincolour:
+    for (i = 0; i < state->next_go; ++i) {
+        if (state->guesses[i]->feedback[0])
+            goto next_iteration;
+        for (j = 0; j < state->params.npegs; ++j)
+            if (state->guesses[i]->pegs[j] != mincolour)
+                goto next_iteration;
+        ++mincolour;
+        goto increase_mincolour;
+    next_iteration:
+        ;
     }
-    nc_place = mark_pegs(to->guesses[from->next_go], to->solution, to->params.ncolours);
 
-    if (nc_place == to->solution->npegs) {
-        to->solved = 1; /* win! */
-    } else {
-        to->next_go = from->next_go + 1;
-        if (to->next_go >= to->params.nguesses)
-            to->solved = 1; /* 'lose' so we show the pegs. */
+    if (!ui->hint) {
+        ui->hint = new_pegrow(state->params.npegs);
+        for (i = 0; i < state->params.npegs; ++i)
+            ui->hint->pegs[i] = 1;
     }
 
-    for (i = 0; i < to->solution->npegs; i++) {
-        if (!ui->holds[i] || to->solved) {
-            ui->curr_pegs->pegs[i] = 0;
-            ncleared++;
+    while (ui->hint->pegs[0] <= state->params.ncolours) {
+        for (i = 0; i < state->next_go; ++i) {
+            mark_pegs(ui->hint, state->guesses[i], maxcolour);
+            for (j = 0; j < state->params.npegs; ++j)
+                if (ui->hint->feedback[j] != state->guesses[i]->feedback[j])
+                    goto increment_pegrow;
         }
-        if (to->solved) ui->holds[i] = 0;
+        /* a valid guess was found; install it and return */
+        for (i = 0; i < state->params.npegs; ++i)
+            ui->curr_pegs->pegs[i] = ui->hint->pegs[i];
+
+        ui->markable = TRUE;
+        ui->peg_cur = state->params.npegs;
+        ui->display_cur = 1;
+        return;
+
+    increment_pegrow:
+        for (i = ui->hint->npegs;
+             ++ui->hint->pegs[--i], i && ui->hint->pegs[i] > maxcolour;
+             ui->hint->pegs[i] = mincolour);
     }
-    if (ncleared) {
-        ui->markable = 0;
-        if (ui->peg_cur == to->solution->npegs)
-            ui->peg_cur--;
+    /* No solution is compatible with the given hints.  Impossible! */
+    /* (hack new_game_desc to create invalid solutions to get here) */
+
+    /* For some values of npegs and ncolours, the hinting function takes a
+     * long time to complete.  To visually indicate completion with failure,
+     * should it ever happen, update the ui in some trivial way.  This gives
+     * the user a sense of broken(ish)ness and futility. */
+    if (!ui->display_cur) {
+        ui->display_cur = 1;
+    } else if (state->params.npegs == 1) {
+        ui->display_cur = 0;
+    } else {
+        ui->peg_cur = (ui->peg_cur + 1) % state->params.npegs;
     }
-
-    return to;
 }
 
-static game_state *make_move(game_state *from, game_ui *ui, game_drawstate *ds,
-                             int x, int y, int button)
+static char *interpret_move(const game_state *from, game_ui *ui,
+                            const game_drawstate *ds,
+                            int x, int y, int button)
 {
     int over_col = 0;           /* one-indexed */
     int over_guess = -1;        /* zero-indexed */
+    int over_past_guess_y = -1; /* zero-indexed */
+    int over_past_guess_x = -1; /* zero-indexed */
     int over_hint = 0;          /* zero or one */
-    game_state *ret = NULL;
+    char *ret = NULL;
 
     int guess_ox = GUESS_X(from->next_go, 0);
     int guess_oy = GUESS_Y(from->next_go, 0);
 
+    /*
+     * Enable or disable labels on colours.
+     */
+    if (button == 'l' || button == 'L') {
+        ui->show_labels = !ui->show_labels;
+        return "";
+    }
+
     if (from->solved) return NULL;
 
-    if (x >= COL_OX && x <= (COL_OX + COL_W) &&
-        y >= COL_OY && y <= (COL_OY + COL_H)) {
+    if (x >= COL_OX && x < (COL_OX + COL_W) &&
+        y >= COL_OY && y < (COL_OY + COL_H)) {
         over_col = ((y - COL_OY) / PEGOFF) + 1;
+        assert(over_col >= 1 && over_col <= ds->colours->npegs);
     } else if (x >= guess_ox &&
-               y >= guess_oy && y <= (guess_oy + GUESS_H)) {
-        if (x <= (guess_ox + GUESS_W)) {
+               y >= guess_oy && y < (guess_oy + GUESS_H)) {
+        if (x < (guess_ox + GUESS_W)) {
             over_guess = (x - guess_ox) / PEGOFF;
+            assert(over_guess >= 0 && over_guess < ds->solution->npegs);
         } else {
             over_hint = 1;
         }
+    } else if (x >= guess_ox && x < (guess_ox + GUESS_W) &&
+               y >= GUESS_OY && y < guess_oy) {
+        over_past_guess_y = (y - GUESS_OY) / PEGOFF;
+        over_past_guess_x = (x - guess_ox) / PEGOFF;
+        assert(over_past_guess_y >= 0 && over_past_guess_y < from->next_go);
+        assert(over_past_guess_x >= 0 && over_past_guess_x < ds->solution->npegs);
     }
-    debug(("make_move: over_col %d, over_guess %d, over_hint %d",
-           over_col, over_guess, over_hint));
+    debug(("make_move: over_col %d, over_guess %d, over_hint %d,"
+           " over_past_guess (%d,%d)", over_col, over_guess, over_hint,
+           over_past_guess_x, over_past_guess_y));
 
     assert(ds->blit_peg);
 
@@ -516,46 +813,64 @@ static game_state *make_move(game_state *from, game_ui *ui, game_drawstate *ds,
     if (button == LEFT_BUTTON) {
         if (over_col > 0) {
             ui->drag_col = over_col;
+            ui->drag_opeg = -1;
             debug(("Start dragging from colours"));
         } else if (over_guess > -1) {
             int col = ui->curr_pegs->pegs[over_guess];
             if (col) {
                 ui->drag_col = col;
+                ui->drag_opeg = over_guess;
                 debug(("Start dragging from a guess"));
             }
+        } else if (over_past_guess_y > -1) {
+            int col =
+                from->guesses[over_past_guess_y]->pegs[over_past_guess_x];
+            if (col) {
+                ui->drag_col = col;
+                ui->drag_opeg = -1;
+                debug(("Start dragging from a past guess"));
+            }
         }
         if (ui->drag_col) {
             ui->drag_x = x;
             ui->drag_y = y;
             debug(("Start dragging, col = %d, (%d,%d)",
                    ui->drag_col, ui->drag_x, ui->drag_y));
-            ret = from;
+            ret = "";
         }
     } else if (button == LEFT_DRAG && ui->drag_col) {
         ui->drag_x = x;
         ui->drag_y = y;
         debug(("Keep dragging, (%d,%d)", ui->drag_x, ui->drag_y));
-        ret = from;
+        ret = "";
     } else if (button == LEFT_RELEASE && ui->drag_col) {
         if (over_guess > -1) {
             debug(("Dropping colour %d onto guess peg %d",
                    ui->drag_col, over_guess));
-            set_peg(ui, over_guess, ui->drag_col);
+            set_peg(&from->params, ui, over_guess, ui->drag_col);
+        } else {
+            if (ui->drag_opeg > -1) {
+                debug(("Removing colour %d from peg %d",
+                       ui->drag_col, ui->drag_opeg));
+                set_peg(&from->params, ui, ui->drag_opeg, 0);
+            }
         }
         ui->drag_col = 0;
+        ui->drag_opeg = -1;
+        ui->display_cur = 0;
         debug(("Stop dragging."));
-        ret = from;
+        ret = "";
     } else if (button == RIGHT_BUTTON) {
         if (over_guess > -1) {
             /* we use ths feedback in the game_ui to signify
              * 'carry this peg to the next guess as well'. */
             ui->holds[over_guess] = 1 - ui->holds[over_guess];
-            ret = from;
+            ret = "";
         }
     } else if (button == LEFT_RELEASE && over_hint && ui->markable) {
         /* NB this won't trigger if on the end of a drag; that's on
          * purpose, in case you drop by mistake... */
-        ret = mark_move(from, ui);
+        ret = encode_move(from, ui);
     }
 
     /* keyboard input */
@@ -565,7 +880,10 @@ static game_state *make_move(game_state *from, game_ui *ui, game_drawstate *ds,
             ui->colour_cur++;
         if (button == CURSOR_UP && ui->colour_cur > 0)
             ui->colour_cur--;
-        ret = from;
+        ret = "";
+    } else if (button == 'h' || button == 'H' || button == '?') {
+        compute_hint(from, ui);
+        ret = "";
     } else if (button == CURSOR_LEFT || button == CURSOR_RIGHT) {
         int maxcur = from->params.npegs;
         if (ui->markable) maxcur++;
@@ -575,19 +893,76 @@ static game_state *make_move(game_state *from, game_ui *ui, game_drawstate *ds,
             ui->peg_cur++;
         if (button == CURSOR_LEFT && ui->peg_cur > 0)
             ui->peg_cur--;
-        ret = from;
-    } else if (button == CURSOR_SELECT || button == ' ' || button == '\r' ||
-               button == '\n') {
+        ret = "";
+    } else if (IS_CURSOR_SELECT(button)) {
+        ui->display_cur = 1;
         if (ui->peg_cur == from->params.npegs) {
-            ret = mark_move(from, ui);
+            ret = encode_move(from, ui);
         } else {
-            set_peg(ui, ui->peg_cur, ui->colour_cur+1);
-            ret = from;
+            set_peg(&from->params, ui, ui->peg_cur, ui->colour_cur+1);
+            ret = "";
         }
+    } else if (button == 'D' || button == 'd' || button == '\b') {
+        ui->display_cur = 1;
+        set_peg(&from->params, ui, ui->peg_cur, 0);
+        ret = "";
+    } else if (button == CURSOR_SELECT2) {
+        if (ui->peg_cur == from->params.npegs)
+            return NULL;
+        ui->display_cur = 1;
+        ui->holds[ui->peg_cur] = 1 - ui->holds[ui->peg_cur];
+        ret = "";
     }
     return ret;
 }
 
+static game_state *execute_move(const game_state *from, const char *move)
+{
+    int i, nc_place;
+    game_state *ret;
+    const char *p;
+
+    if (!strcmp(move, "S")) {
+       ret = dup_game(from);
+       ret->solved = -1;
+       return ret;
+    } else if (move[0] == 'G') {
+       p = move+1;
+
+       ret = dup_game(from);
+
+       for (i = 0; i < from->solution->npegs; i++) {
+           int val = atoi(p);
+           int min_colour = from->params.allow_blank? 0 : 1;
+           if (val < min_colour || val > from->params.ncolours) {
+               free_game(ret);
+               return NULL;
+           }
+           ret->guesses[from->next_go]->pegs[i] = atoi(p);
+           while (*p && isdigit((unsigned char)*p)) p++;
+            if (*p == '_') {
+                ret->holds[i] = 1;
+                p++;
+            } else
+                ret->holds[i] = 0;
+           if (*p == ',') p++;
+       }
+
+       nc_place = mark_pegs(ret->guesses[from->next_go], ret->solution, ret->params.ncolours);
+
+       if (nc_place == ret->solution->npegs) {
+           ret->solved = +1; /* win! */
+       } else {
+           ret->next_go = from->next_go + 1;
+           if (ret->next_go >= ret->params.nguesses)
+               ret->solved = -1; /* lose, meaning we show the pegs. */
+       }
+
+       return ret;
+    } else
+       return NULL;
+}
+
 /* ----------------------------------------------------------------------
  * Drawing routines.
  */
@@ -601,18 +976,18 @@ static game_state *make_move(game_state *from, game_ui *ui, game_drawstate *ds,
 
 #define BORDER    0.5
 
-static void game_size(game_params *params, game_drawstate *ds,
-                      int *x, int *y, int expand)
+static void game_compute_size(const game_params *params, int tilesize,
+                              int *x, int *y)
 {
-    double hmul, vmul_c, vmul_g, vmul, szx, szy;
-    int sz, colh, guessh;
+    double hmul, vmul_c, vmul_g, vmul;
+    int hintw = (params->npegs+1)/2;
 
     hmul = BORDER   * 2.0 +               /* border */
            1.0      * 2.0 +               /* vertical colour bar */
            1.0      * params->npegs +     /* guess pegs */
            PEG_GAP  * params->npegs +     /* guess gaps */
-           PEG_HINT * ds->hintw +         /* hint pegs */
-           PEG_GAP  * (ds->hintw - 1);    /* hint gaps */
+           PEG_HINT * hintw +             /* hint pegs */
+           PEG_GAP  * (hintw - 1);        /* hint gaps */
 
     vmul_c = BORDER  * 2.0 +                    /* border */
              1.0     * params->ncolours +       /* colour pegs */
@@ -624,13 +999,16 @@ static void game_size(game_params *params, game_drawstate *ds,
 
     vmul = max(vmul_c, vmul_g);
 
-    szx = *x / hmul;
-    szy = *y / vmul;
-    sz = max(min((int)szx, (int)szy), 1);
-    if (expand)
-        ds->pegsz = sz;
-    else
-        ds->pegsz = min(sz, PEG_PREFER_SZ);
+    *x = (int)ceil((double)tilesize * hmul);
+    *y = (int)ceil((double)tilesize * vmul);
+}
+
+static void game_set_size(drawing *dr, game_drawstate *ds,
+                          const game_params *params, int tilesize)
+{
+    int colh, guessh;
+
+    ds->pegsz = tilesize;
 
     ds->hintsz = (int)((double)ds->pegsz * PEG_HINT);
     ds->gapsz  = (int)((double)ds->pegsz * PEG_GAP);
@@ -639,85 +1017,87 @@ static void game_size(game_params *params, game_drawstate *ds,
     ds->pegrad  = (ds->pegsz -1)/2; /* radius of peg to fit in pegsz (which is 2r+1) */
     ds->hintrad = (ds->hintsz-1)/2;
 
-    *x = (int)((double)ds->pegsz * hmul);
-    *y = (int)((double)ds->pegsz * vmul);
-
-    ds->w = *x; ds->h = *y;
-
     colh = ((ds->pegsz + ds->gapsz) * params->ncolours) - ds->gapsz;
     guessh = ((ds->pegsz + ds->gapsz) * params->nguesses);      /* guesses */
     guessh += ds->gapsz + ds->pegsz;                            /* solution */
 
+    game_compute_size(params, tilesize, &ds->w, &ds->h);
     ds->colx = ds->border;
-    ds->coly = (*y - colh) / 2;
+    ds->coly = (ds->h - colh) / 2;
 
     ds->guessx = ds->solnx = ds->border + ds->pegsz * 2;     /* border + colours */
-    ds->guessy = (*y - guessh) / 2;
+    ds->guessy = (ds->h - guessh) / 2;
     ds->solny = ds->guessy + ((ds->pegsz + ds->gapsz) * params->nguesses) + ds->gapsz;
 
-    if (ds->pegsz > 0) {
-        if (ds->blit_peg) blitter_free(ds->blit_peg);
-        ds->blit_peg = blitter_new(ds->pegsz, ds->pegsz);
-    }
+    assert(ds->pegsz > 0);
+    assert(!ds->blit_peg);             /* set_size is never called twice */
+    ds->blit_peg = blitter_new(dr, ds->pegsz+2, ds->pegsz+2);
 }
 
-static float *game_colours(frontend *fe, game_state *state, int *ncolours)
+static float *game_colours(frontend *fe, int *ncolours)
 {
-    float *ret = snewn(3 * NCOLOURS, float);
+    float *ret = snewn(3 * NCOLOURS, float), max;
+    int i;
 
     frontend_default_colour(fe, &ret[COL_BACKGROUND * 3]);
 
-    ret[COL_1 * 3 + 0] = 0.0F;
+    /* red */
+    ret[COL_1 * 3 + 0] = 1.0F;
     ret[COL_1 * 3 + 1] = 0.0F;
-    ret[COL_1 * 3 + 2] = 1.0F;
+    ret[COL_1 * 3 + 2] = 0.0F;
 
-    ret[COL_2 * 3 + 0] = 0.0F;
-    ret[COL_2 * 3 + 1] = 0.5F;
+    /* yellow */
+    ret[COL_2 * 3 + 0] = 1.0F;
+    ret[COL_2 * 3 + 1] = 1.0F;
     ret[COL_2 * 3 + 2] = 0.0F;
 
-    ret[COL_3 * 3 + 0] = 1.0F;
-    ret[COL_3 * 3 + 1] = 0.0F;
+    /* green */
+    ret[COL_3 * 3 + 0] = 0.0F;
+    ret[COL_3 * 3 + 1] = 1.0F;
     ret[COL_3 * 3 + 2] = 0.0F;
 
-    ret[COL_4 * 3 + 0] = 1.0F;
-    ret[COL_4 * 3 + 1] = 1.0F;
-    ret[COL_4 * 3 + 2] = 0.0F;
+    /* blue */
+    ret[COL_4 * 3 + 0] = 0.2F;
+    ret[COL_4 * 3 + 1] = 0.3F;
+    ret[COL_4 * 3 + 2] = 1.0F;
 
+    /* orange */
     ret[COL_5 * 3 + 0] = 1.0F;
-    ret[COL_5 * 3 + 1] = 0.0F;
-    ret[COL_5 * 3 + 2] = 1.0F;
+    ret[COL_5 * 3 + 1] = 0.5F;
+    ret[COL_5 * 3 + 2] = 0.0F;
 
-    ret[COL_6 * 3 + 0] = 0.0F;
-    ret[COL_6 * 3 + 1] = 1.0F;
-    ret[COL_6 * 3 + 2] = 1.0F;
+    /* purple */
+    ret[COL_6 * 3 + 0] = 0.5F;
+    ret[COL_6 * 3 + 1] = 0.0F;
+    ret[COL_6 * 3 + 2] = 0.7F;
 
+    /* brown */
     ret[COL_7 * 3 + 0] = 0.5F;
-    ret[COL_7 * 3 + 1] = 0.5F;
-    ret[COL_7 * 3 + 2] = 1.0F;
+    ret[COL_7 * 3 + 1] = 0.3F;
+    ret[COL_7 * 3 + 2] = 0.3F;
 
-    ret[COL_8 * 3 + 0] = 0.5F;
-    ret[COL_8 * 3 + 1] = 1.0F;
-    ret[COL_8 * 3 + 2] = 0.5F;
+    /* light blue */
+    ret[COL_8 * 3 + 0] = 0.4F;
+    ret[COL_8 * 3 + 1] = 0.8F;
+    ret[COL_8 * 3 + 2] = 1.0F;
 
-    ret[COL_9 * 3 + 0] = 1.0F;
-    ret[COL_9 * 3 + 1] = 0.5F;
-    ret[COL_9 * 3 + 2] = 0.5F;
+    /* light green */
+    ret[COL_9 * 3 + 0] = 0.7F;
+    ret[COL_9 * 3 + 1] = 1.0F;
+    ret[COL_9 * 3 + 2] = 0.7F;
 
+    /* pink */
     ret[COL_10 * 3 + 0] = 1.0F;
-    ret[COL_10 * 3 + 1] = 1.0F;
+    ret[COL_10 * 3 + 1] = 0.6F;
     ret[COL_10 * 3 + 2] = 1.0F;
 
     ret[COL_FRAME * 3 + 0] = 0.0F;
     ret[COL_FRAME * 3 + 1] = 0.0F;
     ret[COL_FRAME * 3 + 2] = 0.0F;
 
-    ret[COL_HIGHLIGHT * 3 + 0] = 1.0F;
-    ret[COL_HIGHLIGHT * 3 + 1] = 1.0F;
-    ret[COL_HIGHLIGHT * 3 + 2] = 1.0F;
-
-    ret[COL_LOWLIGHT * 3 + 0] = ret[COL_BACKGROUND * 3 + 0] * 2.0 / 3.0;
-    ret[COL_LOWLIGHT * 3 + 1] = ret[COL_BACKGROUND * 3 + 1] * 2.0 / 3.0;
-    ret[COL_LOWLIGHT * 3 + 2] = ret[COL_BACKGROUND * 3 + 2] * 2.0 / 3.0;
+    ret[COL_CURSOR * 3 + 0] = 0.0F;
+    ret[COL_CURSOR * 3 + 1] = 0.0F;
+    ret[COL_CURSOR * 3 + 2] = 0.0F;
 
     ret[COL_FLASH * 3 + 0] = 0.5F;
     ret[COL_FLASH * 3 + 1] = 1.0F;
@@ -727,11 +1107,7 @@ static float *game_colours(frontend *fe, game_state *state, int *ncolours)
     ret[COL_HOLD * 3 + 1] = 0.5F;
     ret[COL_HOLD * 3 + 2] = 0.5F;
 
-    ret[COL_EMPTY * 3 + 0] = ret[COL_BACKGROUND * 3 + 0] * 2.0 / 3.0;
-    ret[COL_EMPTY * 3 + 1] = ret[COL_BACKGROUND * 3 + 1] * 2.0 / 3.0;
-    ret[COL_EMPTY * 3 + 2] = ret[COL_BACKGROUND * 3 + 2] * 2.0 / 3.0;
-
-    ret[COL_CORRECTPLACE*3 + 0] = 1.0F;
+    ret[COL_CORRECTPLACE*3 + 0] = 0.0F;
     ret[COL_CORRECTPLACE*3 + 1] = 0.0F;
     ret[COL_CORRECTPLACE*3 + 2] = 0.0F;
 
@@ -739,11 +1115,30 @@ static float *game_colours(frontend *fe, game_state *state, int *ncolours)
     ret[COL_CORRECTCOLOUR*3 + 1] = 1.0F;
     ret[COL_CORRECTCOLOUR*3 + 2] = 1.0F;
 
+    /* We want to make sure we can distinguish COL_CORRECTCOLOUR
+     * (which we hard-code as white) from COL_BACKGROUND (which
+     * could default to white on some platforms).
+     * Code borrowed from fifteen.c. */
+    max = ret[COL_BACKGROUND*3];
+    for (i = 1; i < 3; i++)
+        if (ret[COL_BACKGROUND*3+i] > max)
+            max = ret[COL_BACKGROUND*3+i];
+    if (max * 1.2F > 1.0F) {
+        for (i = 0; i < 3; i++)
+            ret[COL_BACKGROUND*3+i] /= (max * 1.2F);
+    }
+
+    /* We also want to be able to tell the difference between BACKGROUND
+     * and EMPTY, for similar distinguishing-hint reasons. */
+    ret[COL_EMPTY * 3 + 0] = ret[COL_BACKGROUND * 3 + 0] * 2.0F / 3.0F;
+    ret[COL_EMPTY * 3 + 1] = ret[COL_BACKGROUND * 3 + 1] * 2.0F / 3.0F;
+    ret[COL_EMPTY * 3 + 2] = ret[COL_BACKGROUND * 3 + 2] * 2.0F / 3.0F;
+
     *ncolours = NCOLOURS;
     return ret;
 }
 
-static game_drawstate *game_new_drawstate(game_state *state)
+static game_drawstate *game_new_drawstate(drawing *dr, const game_state *state)
 {
     struct game_drawstate *ds = snew(struct game_drawstate);
     int i;
@@ -763,39 +1158,65 @@ static game_drawstate *game_new_drawstate(game_state *state)
 
     ds->hintw = (state->params.npegs+1)/2; /* must round up */
 
-    ds->holds = snewn(state->params.npegs, int);
-    memset(ds->holds, 0, state->params.npegs*sizeof(int));
-
     ds->blit_peg = NULL;
 
     return ds;
 }
 
-static void game_free_drawstate(game_drawstate *ds)
+static void game_free_drawstate(drawing *dr, game_drawstate *ds)
 {
     int i;
 
-    if (ds->blit_peg) blitter_free(ds->blit_peg);
+    if (ds->blit_peg) blitter_free(dr, ds->blit_peg);
     free_pegrow(ds->colours);
     free_pegrow(ds->solution);
     for (i = 0; i < ds->nguesses; i++)
         free_pegrow(ds->guesses[i]);
-    sfree(ds->holds);
     sfree(ds->guesses);
     sfree(ds);
 }
 
-static void draw_peg(frontend *fe, game_drawstate *ds, int cx, int cy, int col)
+static void draw_peg(drawing *dr, game_drawstate *ds, int cx, int cy,
+                    int moving, int labelled, int col)
+{
+    /*
+     * Some platforms antialias circles, which means we shouldn't
+     * overwrite a circle of one colour with a circle of another
+     * colour without erasing the background first. However, if the
+     * peg is the one being dragged, we don't erase the background
+     * because we _want_ it to alpha-blend nicely into whatever's
+     * behind it.
+     */
+    if (!moving)
+        draw_rect(dr, cx-CGAP, cy-CGAP, PEGSZ+CGAP*2, PEGSZ+CGAP*2,
+                  COL_BACKGROUND);
+    if (PEGRAD > 0) {
+        draw_circle(dr, cx+PEGRAD, cy+PEGRAD, PEGRAD,
+                   COL_EMPTY + col, (col ? COL_FRAME : COL_EMPTY));
+    } else
+        draw_rect(dr, cx, cy, PEGSZ, PEGSZ, COL_EMPTY + col);
+
+    if (labelled && col) {
+        char buf[2];
+        buf[0] = 'a'-1 + col;
+        buf[1] = '\0';
+        draw_text(dr, cx+PEGRAD, cy+PEGRAD, FONT_VARIABLE, PEGRAD,
+                  ALIGN_HCENTRE|ALIGN_VCENTRE, COL_FRAME, buf);
+    }
+
+    draw_update(dr, cx-CGAP, cy-CGAP, PEGSZ+CGAP*2, PEGSZ+CGAP*2);
+}
+
+static void draw_cursor(drawing *dr, game_drawstate *ds, int x, int y)
 {
-    if (PEGRAD > 0)
-        draw_circle(fe, cx+PEGRAD, cy+PEGRAD, PEGRAD, 1, COL_EMPTY + col);
-    else
-        draw_rect(fe, cx, cy, PEGSZ, PEGSZ, COL_EMPTY + col);
-    draw_update(fe, cx, cy, PEGSZ, PEGSZ);
+    draw_circle(dr, x+PEGRAD, y+PEGRAD, PEGRAD+CGAP, -1, COL_CURSOR);
+
+    draw_update(dr, x-CGAP, y-CGAP, PEGSZ+CGAP*2, PEGSZ+CGAP*2);
 }
 
-static void guess_redraw(frontend *fe, game_drawstate *ds, int guess,
-                         pegrow src, int force)
+static void guess_redraw(drawing *dr, game_drawstate *ds, int guess,
+                         pegrow src, int *holds, int cur_col, int force,
+                         int labelled)
 {
     pegrow dest;
     int rowx, rowy, i, scol;
@@ -813,27 +1234,75 @@ static void guess_redraw(frontend *fe, game_drawstate *ds, int guess,
 
     for (i = 0; i < dest->npegs; i++) {
         scol = src ? src->pegs[i] : 0;
-        if ((dest->pegs[i] != scol) || force)
-           draw_peg(fe, ds, rowx + PEGOFF * i, rowy, scol);
+        if (i == cur_col)
+            scol |= 0x1000;
+        if (holds && holds[i])
+            scol |= 0x2000;
+        if (labelled)
+            scol |= 0x4000;
+        if ((dest->pegs[i] != scol) || force) {
+           draw_peg(dr, ds, rowx + PEGOFF * i, rowy, FALSE, labelled,
+                     scol &~ 0x7000);
+            /*
+             * Hold marker.
+             */
+            draw_rect(dr, rowx + PEGOFF * i, rowy + PEGSZ + ds->gapsz/2,
+                      PEGSZ, 2, (scol & 0x2000 ? COL_HOLD : COL_BACKGROUND));
+            draw_update(dr, rowx + PEGOFF * i, rowy + PEGSZ + ds->gapsz/2,
+                        PEGSZ, 2);
+            if (scol & 0x1000)
+                draw_cursor(dr, ds, rowx + PEGOFF * i, rowy);
+        }
         dest->pegs[i] = scol;
     }
 }
 
-static void hint_redraw(frontend *fe, game_drawstate *ds, int guess,
-                        pegrow src, int force, int emptycol)
+static void hint_redraw(drawing *dr, game_drawstate *ds, int guess,
+                        pegrow src, int force, int cursor, int markable)
 {
     pegrow dest = ds->guesses[guess];
     int rowx, rowy, i, scol, col, hintlen;
+    int need_redraw;
+    int emptycol = (markable ? COL_FLASH : COL_EMPTY);
 
     if (src) assert(src->npegs == dest->npegs);
 
     hintlen = (dest->npegs + 1)/2;
 
+    /*
+     * Because of the possible presence of the cursor around this
+     * entire section, we redraw all or none of it but never part.
+     */
+    need_redraw = FALSE;
+
     for (i = 0; i < dest->npegs; i++) {
         scol = src ? src->feedback[i] : 0;
-        col = (scol == FEEDBACK_CORRECTPLACE) ? COL_CORRECTPLACE :
-              (scol == FEEDBACK_CORRECTCOLOUR) ? COL_CORRECTCOLOUR : emptycol;
+        if (i == 0 && cursor)
+            scol |= 0x1000;
+        if (i == 0 && markable)
+            scol |= 0x2000;
         if ((scol != dest->feedback[i]) || force) {
+            need_redraw = TRUE;
+        }
+        dest->feedback[i] = scol;
+    }
+
+    if (need_redraw) {
+        int hinth = HINTSZ + GAP + HINTSZ;
+        int hx,hy,hw,hh;
+
+        hx = HINT_X(guess)-GAP; hy = HINT_Y(guess)-GAP;
+        hw = HINT_W+GAP*2; hh = hinth+GAP*2;
+
+        /* erase a large background rectangle */
+        draw_rect(dr, hx, hy, hw, hh, COL_BACKGROUND);
+
+        for (i = 0; i < dest->npegs; i++) {
+            scol = src ? src->feedback[i] : 0;
+            col = ((scol == FEEDBACK_CORRECTPLACE) ? COL_CORRECTPLACE :
+                   (scol == FEEDBACK_CORRECTCOLOUR) ? COL_CORRECTCOLOUR :
+                   emptycol);
+
             rowx = HINT_X(guess);
             rowy = HINT_Y(guess);
             if (i < hintlen) {
@@ -842,162 +1311,115 @@ static void hint_redraw(frontend *fe, game_drawstate *ds, int guess,
                 rowx += HINTOFF * (i - hintlen);
                 rowy += HINTOFF;
             }
-            if (HINTRAD > 0)
-                draw_circle(fe, rowx+HINTRAD, rowy+HINTRAD, HINTRAD, 1, col);
-            else
-                draw_rect(fe, rowx, rowy, HINTSZ, HINTSZ, col);
-            draw_update(fe, rowx, rowy, HINTSZ, HINTSZ);
+            if (HINTRAD > 0) {
+                draw_circle(dr, rowx+HINTRAD, rowy+HINTRAD, HINTRAD, col,
+                            (col == emptycol ? emptycol : COL_FRAME));
+            } else {
+                draw_rect(dr, rowx, rowy, HINTSZ, HINTSZ, col);
+            }
         }
-        dest->feedback[i] = scol;
-    }
-}
-
-static void hold_redraw(frontend *fe, game_drawstate *ds, int guess, int *src, int force)
-{
-    int shold, col, ox, oy, i;
-
-    if (guess >= ds->nguesses)
-        return;
-
-    for (i = 0; i < ds->solution->npegs; i++) {
-        shold = src ? src[i] : 0;
-        col = shold ? COL_HOLD : COL_BACKGROUND;
-        if ((shold != ds->holds[i]) || force) {
-            ox = GUESS_X(guess, i);
-            oy = GUESS_Y(guess, i) + PEGSZ + ds->gapsz/2;
-
-            draw_rect(fe, ox, oy, PEGSZ, 2, col);
-            draw_update(fe, ox, oy, PEGSZ, 2);
+        if (cursor) {
+            int x1,y1,x2,y2;
+            x1 = hx + CGAP; y1 = hy + CGAP;
+            x2 = hx + hw - CGAP; y2 = hy + hh - CGAP;
+            draw_line(dr, x1, y1, x2, y1, COL_CURSOR);
+            draw_line(dr, x2, y1, x2, y2, COL_CURSOR);
+            draw_line(dr, x2, y2, x1, y2, COL_CURSOR);
+            draw_line(dr, x1, y2, x1, y1, COL_CURSOR);
         }
-        if (src) ds->holds[i] = shold;
+
+        draw_update(dr, hx, hy, hw, hh);
     }
 }
 
-static void currmove_redraw(frontend *fe, game_drawstate *ds, int guess, int col)
+static void currmove_redraw(drawing *dr, game_drawstate *ds, int guess, int col)
 {
     int ox = GUESS_X(guess, 0), oy = GUESS_Y(guess, 0), off = PEGSZ/4;
 
-    draw_rect(fe, ox-off-1, oy, 2, PEGSZ, col);
-    draw_update(fe, ox-off-1, oy, 2, PEGSZ);
-}
-
-static void cur_redraw(frontend *fe, game_drawstate *ds,
-                       int x, int y, int erase)
-{
-    int cgap = ds->gapsz / 2;
-    int x1, y1, x2, y2, hi, lo;
-
-    x1 = x-cgap; x2 = x+PEGSZ+cgap;
-    y1 = y-cgap; y2 = y+PEGSZ+cgap;
-    hi = erase ? COL_BACKGROUND : COL_HIGHLIGHT;
-    lo = erase ? COL_BACKGROUND : COL_LOWLIGHT;
-
-    draw_line(fe, x1, y1, x2, y1, hi);
-    draw_line(fe, x2, y1, x2, y2, lo);
-    draw_line(fe, x2, y2, x1, y2, lo);
-    draw_line(fe, x1, y2, x1, y1, hi);
-
-    draw_update(fe, x1, y1, x2, y2);
+    draw_rect(dr, ox-off-1, oy, 2, PEGSZ, col);
+    draw_update(dr, ox-off-1, oy, 2, PEGSZ);
 }
 
-static void game_redraw(frontend *fe, game_drawstate *ds, game_state *oldstate,
-                       game_state *state, int dir, game_ui *ui,
-                       float animtime, float flashtime)
+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, cur_erase = 0, cur_draw = 0, new_move, last_go;
+    int i, new_move;
 
     new_move = (state->next_go != ds->next_go) || !ds->started;
-    last_go = (state->next_go == state->params.nguesses-1);
 
     if (!ds->started) {
-      draw_rect(fe, 0, 0, ds->w, ds->h, COL_BACKGROUND);
-      draw_rect(fe, SOLN_OX, SOLN_OY - ds->gapsz - 1, SOLN_W, 2, COL_FRAME);
-      draw_update(fe, 0, 0, ds->w, ds->h);
+      draw_rect(dr, 0, 0, ds->w, ds->h, COL_BACKGROUND);
+      draw_rect(dr, SOLN_OX, SOLN_OY - ds->gapsz - 1, SOLN_W, 2, COL_FRAME);
+      draw_update(dr, 0, 0, ds->w, ds->h);
     }
 
     if (ds->drag_col != 0) {
         debug(("Loading from blitter."));
-        blitter_load(fe, ds->blit_peg, ds->blit_ox, ds->blit_oy);
-        draw_update(fe, ds->blit_ox, ds->blit_oy, PEGSZ, PEGSZ);
+        blitter_load(dr, ds->blit_peg, ds->blit_ox, ds->blit_oy);
+        draw_update(dr, ds->blit_ox, ds->blit_oy, PEGSZ, PEGSZ);
     }
 
     /* draw the colours */
     for (i = 0; i < state->params.ncolours; i++) {
-        if (ds->colours->pegs[i] != i+1) {
-           draw_peg(fe, ds, COL_X(i), COL_Y(i), i+1);
-            ds->colours->pegs[i] = i+1;
+        int val = i+1;
+        if (ui->display_cur && ui->colour_cur == i)
+            val |= 0x1000;
+        if (ui->show_labels)
+            val |= 0x2000;
+        if (ds->colours->pegs[i] != val) {
+           draw_peg(dr, ds, COL_X(i), COL_Y(i), FALSE, ui->show_labels, i+1);
+            if (val & 0x1000)
+                draw_cursor(dr, ds, COL_X(i), COL_Y(i));
+            ds->colours->pegs[i] = val;
         }
     }
 
-    /* draw the guesses (so far) and the hints */
-    for (i = 0; i < state->params.nguesses; i++) {
-        if (state->next_go > i || state->solved) {
+    /* draw the guesses (so far) and the hints
+     * (in reverse order to avoid trampling holds, and postponing the
+     * next_go'th to not overrender the top of the circular cursor) */
+    for (i = state->params.nguesses - 1; i >= 0; i--) {
+        if (i < state->next_go || state->solved) {
             /* this info is stored in the game_state already */
-            guess_redraw(fe, ds, i, state->guesses[i], 0);
-            hint_redraw(fe, ds, i, state->guesses[i],
-                        i == (state->next_go-1) ? 1 : 0, COL_EMPTY);
-        } else if (state->next_go == i) {
-            /* this is the one we're on; the (incomplete) guess is
-             * stored in the game_ui. */
-            guess_redraw(fe, ds, i, ui->curr_pegs, 0);
-            hint_redraw(fe, ds, i, NULL, 1, ui->markable ? COL_FLASH : COL_EMPTY);
-        } else {
+            guess_redraw(dr, ds, i, state->guesses[i], NULL, -1, 0,
+                         ui->show_labels);
+            hint_redraw(dr, ds, i, state->guesses[i],
+                        i == (state->next_go-1) ? 1 : 0, FALSE, FALSE);
+        } else if (i > state->next_go) {
             /* we've not got here yet; it's blank. */
-            guess_redraw(fe, ds, i, NULL, 0);
-            hint_redraw(fe, ds, i, NULL, 0, COL_EMPTY);
+            guess_redraw(dr, ds, i, NULL, NULL, -1, 0, ui->show_labels);
+            hint_redraw(dr, ds, i, NULL, 0, FALSE, FALSE);
         }
     }
-
-    /* draw the 'hold' markers */
-    if (state->solved) {
-        hold_redraw(fe, ds, state->next_go, NULL, 1);
-    } else if (new_move) {
-        hold_redraw(fe, ds, ds->next_go, NULL, 1);
-        hold_redraw(fe, ds, state->next_go, last_go ? NULL : ui->holds, 1);
-    } else
-        hold_redraw(fe, ds, state->next_go, last_go ? NULL : ui->holds, 0);
+    if (!state->solved) {
+       /* this is the one we're on; the (incomplete) guess is stored in
+        * the game_ui. */
+       guess_redraw(dr, ds, state->next_go, ui->curr_pegs,
+                    ui->holds, ui->display_cur ? ui->peg_cur : -1, 0,
+                    ui->show_labels);
+       hint_redraw(dr, ds, state->next_go, NULL, 1,
+                   ui->display_cur && ui->peg_cur == state->params.npegs,
+                   ui->markable);
+    }
 
     /* draw the 'current move' and 'able to mark' sign. */
     if (new_move)
-        currmove_redraw(fe, ds, ds->next_go, COL_BACKGROUND);
+        currmove_redraw(dr, ds, ds->next_go, COL_BACKGROUND);
     if (!state->solved)
-        currmove_redraw(fe, ds, state->next_go, COL_HOLD);
+        currmove_redraw(dr, ds, state->next_go, COL_HOLD);
 
     /* draw the solution (or the big rectangle) */
-    if ((state->solved != ds->solved) || !ds->started) {
-        draw_rect(fe, SOLN_OX, SOLN_OY, SOLN_W, SOLN_H,
+    if ((!state->solved ^ !ds->solved) || !ds->started) {
+        draw_rect(dr, SOLN_OX, SOLN_OY, SOLN_W, SOLN_H,
                   state->solved ? COL_BACKGROUND : COL_EMPTY);
-        draw_update(fe, SOLN_OX, SOLN_OY, SOLN_W, SOLN_H);
+        draw_update(dr, SOLN_OX, SOLN_OY, SOLN_W, SOLN_H);
     }
     if (state->solved)
-        guess_redraw(fe, ds, -1, state->solution, !ds->solved);
+        guess_redraw(dr, ds, -1, state->solution, NULL, -1, !ds->solved,
+                     ui->show_labels);
     ds->solved = state->solved;
 
-    if (ui->display_cur && !ds->display_cur)
-        cur_draw = 1;
-    else if (!ui->display_cur && ds->display_cur)
-        cur_erase = 1;
-    else if (ui->display_cur) {
-        if ((state->next_go != ds->next_go) ||
-            (ui->peg_cur != ds->peg_cur) ||
-            (ui->colour_cur != ds->colour_cur)) {
-            cur_erase = 1;
-            cur_draw = 1;
-        }
-    }
-    if (cur_erase) {
-        cur_redraw(fe, ds, COL_X(ds->colour_cur), COL_Y(ds->colour_cur), 1);
-        cur_redraw(fe, ds,
-                   GUESS_X(ds->next_go, ds->peg_cur), GUESS_Y(ds->next_go, ds->peg_cur), 1);
-    }
-    if (cur_draw) {
-        cur_redraw(fe, ds, COL_X(ui->colour_cur), COL_Y(ui->colour_cur), 0);
-        cur_redraw(fe, ds,
-                   GUESS_X(state->next_go, ui->peg_cur), GUESS_Y(state->next_go, ui->peg_cur), 0);
-    }
-    ds->display_cur = ui->display_cur;
-    ds->peg_cur = ui->peg_cur;
-    ds->colour_cur = ui->colour_cur;
     ds->next_go = state->next_go;
 
     /* if ui->drag_col != 0, save the screen to the blitter,
@@ -1005,45 +1427,58 @@ static void game_redraw(frontend *fe, game_drawstate *ds, game_state *oldstate,
     if (ui->drag_col != 0) {
         int ox = ui->drag_x - (PEGSZ/2);
         int oy = ui->drag_y - (PEGSZ/2);
-        debug(("Saving to blitter at (%d,%d)", ox, oy));
-        blitter_save(fe, ds->blit_peg, ox, oy);
-        draw_peg(fe, ds, ox, oy, ui->drag_col);
-
-        ds->blit_ox = ox; ds->blit_oy = oy;
+        ds->blit_ox = ox - 1; ds->blit_oy = oy - 1;
+        debug(("Saving to blitter at (%d,%d)", ds->blit_ox, ds->blit_oy));
+        blitter_save(dr, ds->blit_peg, ds->blit_ox, ds->blit_oy);
+        draw_peg(dr, ds, ox, oy, TRUE, ui->show_labels, ui->drag_col);
     }
     ds->drag_col = ui->drag_col;
 
     ds->started = 1;
 }
 
-static float game_anim_length(game_state *oldstate, game_state *newstate,
-                             int dir, game_ui *ui)
+static float game_anim_length(const game_state *oldstate,
+                              const game_state *newstate, int dir, game_ui *ui)
 {
     return 0.0F;
 }
 
-static float game_flash_length(game_state *oldstate, game_state *newstate,
-                              int dir, game_ui *ui)
+static float game_flash_length(const game_state *oldstate,
+                               const game_state *newstate, int dir, game_ui *ui)
 {
     return 0.0F;
 }
 
-static int game_wants_statusbar(void)
+static int game_status(const game_state *state)
 {
-    return FALSE;
+    /*
+     * We return nonzero whenever the solution has been revealed, even
+     * (on spoiler grounds) if it wasn't guessed correctly. The
+     * correct return value from this function is already in
+     * state->solved.
+     */
+    return state->solved;
 }
 
-static int game_timing_state(game_state *state)
+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 guess
 #endif
 
 const struct game thegame = {
-    "Guess", "games.guess",
+    "Guess", "games.guess", "guess",
     default_params,
     game_fetch_preset,
     decode_params,
@@ -1053,27 +1488,31 @@ const struct game thegame = {
     TRUE, game_configure, custom_params,
     validate_params,
     new_game_desc,
-    game_free_aux_info,
     validate_desc,
     new_game,
     dup_game,
     free_game,
     TRUE, solve_game,
-    FALSE, game_text_format,
+    FALSE, game_can_format_as_text_now, game_text_format,
     new_ui,
     free_ui,
+    encode_ui,
+    decode_ui,
     game_changed_state,
-    make_move,
-    game_size,
+    interpret_move,
+    execute_move,
+    PEG_PREFER_SZ, game_compute_size, game_set_size,
     game_colours,
     game_new_drawstate,
     game_free_drawstate,
     game_redraw,
     game_anim_length,
     game_flash_length,
-    game_wants_statusbar,
+    game_status,
+    FALSE, FALSE, game_print_size, game_print,
+    FALSE,                            /* wants_statusbar */
     FALSE, game_timing_state,
-    0,                                /* mouse_priorities */
+    0,                                /* flags */
 };
 
 /* vim: set shiftwidth=4 tabstop=8: */