1 files changed, 19 insertions, 0 deletions
diff --git a/unequal.c b/unequal.c
index 5e9994f..c1d3a30 100644
--- a/unequal.c
+++ b/unequal.c
@@ -1612,6 +1612,25 @@ static char *interpret_move(const game_state *state, game_ui *ui,
         if (ui->hpencil && GRID(state, nums, ui->hx, ui->hy) > 0)
             return NULL;        /* can't change hints on filled square (!) */
 
+        /*
+         * If you ask to fill a square with what it already contains,
+         * or blank it when it's already empty, that has no effect...
+         */
+        if ((!ui->hpencil || n == 0) &&
+            GRID(state, nums, ui->hx, ui->hy) == n) {
+            bool anypencil = false;
+            int i;
+            for (i = 0; i < state->order; i++)
+                anypencil = anypencil || HINT(state, ui->hx, ui->hy, i);
+            if (!anypencil) {
+                /* ... expect to remove the cursor in mouse mode. */
+                if (!ui->hcursor) {
+                    ui->hshow = false;
+                    return UI_UPDATE;
+                }
+                return NULL;
+            }
+        }
 
         sprintf(buf, "%c%d,%d,%d",
                 (char)(ui->hpencil && n > 0 ? 'P' : 'R'), ui->hx, ui->hy, n);