Move bullet trajectory into bullet update function

src/Dodge/Update.hs

@@ -5,6 +5,7 @@ Description : Simulation update
 -}
 module Dodge.Update ( updateUniverse ) where
 import Dodge.Data
+import Dodge.Bullet
 import Dodge.Update.Cloud
 import Dodge.Machine.Update
 import Dodge.RadarBlip
@@ -217,7 +218,7 @@ updateFlares = flares %~ mapMaybe updateFlare
 updateBullets :: World -> World
 updateBullets w = updateInstantBullets $ set bullets (catMaybes ps) w'
   where 
-    (w',ps) = mapAccumR (\a b -> _buUpdate b a b) w $ _bullets w
+    (w',ps) = mapAccumR (\a b -> updateBullet a b) w $ _bullets w
 
 {- Apply internal particle updates, delete 'Nothing's.  -}
 updateParticles :: World -> World
@@ -297,7 +298,7 @@ intersectSegSegs' _ _ _ = Nothing
 updateInstantBullets :: World -> World
 updateInstantBullets w = case _instantBullets w of
     [] -> w
-    ps -> let (w',ps') = mapAccumR (\a b -> _buUpdate b a b) (w {_instantBullets=[]}) ps
+    ps -> let (w',ps') = mapAccumR (\a b -> updateBullet a b) (w {_instantBullets=[]}) ps
         in updateInstantBullets $ w' & bullets .++~ catMaybes ps'
 
 updateInstantParticles :: World -> World