slight outline for stones

config.json

@@ -15,6 +15,7 @@
     "size_min": 1,
     "size_max": 15,
     "stones": [ [0.05, 0.05, 0.05], [0.95, 0.95, 0.95] ],
+    "outline": [ [0.3,0.3,0.3,0.5],  [0.7, 0.7, 0.7,0.5] ],
     "ghost_alpha": 0.5,
     "eval_colors": [[0.537, 0.129, 0.42], [1, 0, 0], [1, 0.95, 0], [0.117, 0.588, 0]],
     "undo_alpha": 0.5,