Dominosa: add presets for Hard and Extreme difficulty.

I decided not to go all the way up to order-9 Extreme, because that
takes a lot of CPU to generate. People can select it by hand if they
don't mind that.

1 files changed, 2 insertions, 0 deletions

diff --git a/dominosa.c b/dominosa.c
index 2fd2af7..f31af62 100644
--- a/dominosa.c
+++ b/dominosa.c
@@ -142,6 +142,8 @@ static const struct game_params dominosa_presets[] = {
     {  7, DIFF_BASIC   },
     {  8, DIFF_BASIC   },
     {  9, DIFF_BASIC   },
+    {  6, DIFF_HARD    },
+    {  6, DIFF_EXTREME },
 };
 
 static bool game_fetch_preset(int i, char **name, game_params **params_out)