Simplify machine placement

src/Dodge/Data/GenWorld.hs

@@ -33,7 +33,7 @@ data PSType
     | PutMachine
         { _putMachinePoly :: [Point2]
         , _putMachineMachine :: Machine
-        , _putMachineWall :: Wall
+--        , _putMachineWall :: Wall
         , _putMachineMaybeItem :: Maybe Item
         }
     | PutLS LightSource

src/Dodge/Data/Wall.hs

@@ -32,7 +32,7 @@ data Wall = Wall
 
 data Opacity
     = SeeThrough
-    | SeeAbove
+    | SeeAbove  -- these are not drawn themselves, but the "owning" machine or block should draw them
     | DrawnWall {_opDraw :: WallDraw} -- Wall -> SPic
     | Opaque {_opTexture :: Int}
     deriving (Eq, Ord, Show, Read) --Generic, Flat)