Refactor arc shader so it uses only matrix uniform

src/Dodge/Default.hs

@@ -95,7 +95,7 @@ defaultWorld = World
     , _midgroundDecorations = 
         [setDepth (-0.1) $ color orange $ pictures
             [ polygon $ rectNSEW 50 40 140 (-20)
-            , translate 60 45 $ thickArc 0 pi 75 10
+            , translate 60 45 $ scale 0.5 1 $  thickArc 0 pi 75 10
             ]
         ]
     }