Add indicator light to switch doors

src/Dodge/PlacementSpot.hs

@@ -0,0 +1,23 @@
+module Dodge.PlacementSpot where
+import Dodge.LevelGen.Data
+import Geometry
+
+-- TODO rename to any unused link facing out
+anyLnkOutPS :: PlacementSpot
+anyLnkOutPS = PSLnk f (const id) Nothing
+  where
+    f (UnusedLink p a) = Just $ PS p a
+    f _ = Nothing
+    
+fstLnkOut :: PlacementSpot
+fstLnkOut = PSLnk f (const id) Nothing
+  where
+    f (OutLink 0 p a) = Just $ PS p a
+    f _ = Nothing
+
+anyLnkInPS :: Float -- ^ amount to shift inward
+    -> PlacementSpot
+anyLnkInPS x = PSLnk f (const id) Nothing
+  where
+    f (UnusedLink v a) = Just $ PS (v -.- x *.* unitVectorAtAngle (a + 0.5 * pi)) (a+ pi)
+    f _ = Nothing