diff --git a/Intro/Vect.idr b/Intro/Vect.idr
index ff494ab..e626837 100644
--- a/Intro/Vect.idr
+++ b/Intro/Vect.idr
@@ -17,7 +17,6 @@ data Vect : Nat -> Type -> Type where
 
 append : Vect n a -> Vect m a -> Vect (n + m) a
 
-
 {-
 Try to write this using the interactive tools alone:
 
diff --git a/Invaders/Aliens.idr b/Invaders/Aliens.idr
index 18142f3..15489cc 100644
--- a/Invaders/Aliens.idr
+++ b/Invaders/Aliens.idr
@@ -52,7 +52,7 @@ checkHit bs as = checkAll bs as [] []
         checkAll [] as asAcc bsAcc = (bsAcc, as ++ asAcc)
              
 drawAliens : List Alien -> { [SDL_ON] } Eff ()
-drawAliens [] = return ()
+drawAliens [] = pure ()
 drawAliens (a :: as) = do let (x, y) = Alien.position a
                           drawAlien x y
                           drawAliens as
diff --git a/Invaders/Gamestate.idr b/Invaders/Gamestate.idr
index 028cd57..8cc4860 100644
--- a/Invaders/Gamestate.idr
+++ b/Invaders/Gamestate.idr
@@ -54,12 +54,12 @@ removeHit gs = let bs = bullets gs in
                record { bullets = bs', aliens = as' } gs
 
 drawBullets : List (Int, Int) -> { [SDL_ON] } Eff ()
-drawBullets [] = return ()
+drawBullets [] = pure ()
 drawBullets ((x, y) :: bs) = do rectangle red (x-1) (y-4) 2 8
                                 drawBullets bs
 
 drawBombs : List (Int, Int) -> { [SDL_ON] } Eff ()
-drawBombs [] = return ()
+drawBombs [] = pure ()
 drawBombs ((x, y) :: bs) = do rectangle yellow (x-1) (y-4) 2 8
                               drawBombs bs
 
@@ -67,7 +67,7 @@ randomDropBomb : GS ()
 randomDropBomb = randomDrop (map (Alien.position) (aliens !(Gamestate :- get))) 
  where
    randomDrop : List (Int, Int) -> GS ()
-   randomDrop [] = return ()
+   randomDrop [] = pure ()
    randomDrop ((x, y) :: as) 
         = do if (!(rndInt 1 3000) == 100)  
                  then (do s <- Gamestate :- get
@@ -94,7 +94,7 @@ updateGamestate = do gs <- Gamestate :- get
 
 getPos : GS (Int, Int)
 getPos = do s <- Gamestate :- get
-            return (position s)
+            pure (position s)
 
 xmove : Int -> GS ()
 xmove x = do s <- Gamestate :- get
@@ -112,14 +112,14 @@ addBullet = do s <- Gamestate :- get
 
 -- Deal with keypresses from SDL
 process : Maybe Event -> GS Bool
-process (Just AppQuit) = return False
-process (Just (KeyDown KeyLeftArrow))  = do xmove (-2); return True
-process (Just (KeyUp KeyLeftArrow))    = do xmove 0; return True
-process (Just (KeyDown KeyRightArrow)) = do xmove 2; return True
-process (Just (KeyUp KeyRightArrow))   = do xmove 0; return True
-process (Just (KeyDown KeyUpArrow))    = do ymove (-2); return True
-process (Just (KeyUp KeyUpArrow))      = do ymove 0; return True
-process (Just (KeyDown KeyDownArrow))  = do ymove 2; return True
-process (Just (KeyUp KeyDownArrow))    = do ymove 0; return True
-process (Just (KeyDown KeySpace))      = do addBullet; return True 
-process _ = return True
+process (Just AppQuit) = pure False
+process (Just (KeyDown KeyLeftArrow))  = do xmove (-2); pure True
+process (Just (KeyUp KeyLeftArrow))    = do xmove 0; pure True
+process (Just (KeyDown KeyRightArrow)) = do xmove 2; pure True
+process (Just (KeyUp KeyRightArrow))   = do xmove 0; pure True
+process (Just (KeyDown KeyUpArrow))    = do ymove (-2); pure True
+process (Just (KeyUp KeyUpArrow))      = do ymove 0; pure True
+process (Just (KeyDown KeyDownArrow))  = do ymove 2; pure True
+process (Just (KeyUp KeyDownArrow))    = do ymove 0; pure True
+process (Just (KeyDown KeySpace))      = do addBullet; pure True 
+process _ = pure True
diff --git a/Invaders/Rnd.idr b/Invaders/Rnd.idr
index ea1dc97..1295d34 100644
--- a/Invaders/Rnd.idr
+++ b/Invaders/Rnd.idr
@@ -17,6 +17,6 @@ RND = MkEff Int Random
 
 rndInt : Int -> Int -> { [RND] } Eff Int
 rndInt lower upper = do v <- call GetRandom
-                        return (abs (v `prim__sremInt` (upper - lower)) + lower)
+                        pure (abs (v `prim__sremInt` (upper - lower)) + lower)
 
 
diff --git a/Invaders/Starfield.idr b/Invaders/Starfield.idr
index 5f3097b..dc945da 100644
--- a/Invaders/Starfield.idr
+++ b/Invaders/Starfield.idr
@@ -29,7 +29,7 @@ updateStarfield = do xs <- Starfield :- get
                      Starfield :- put xs'
  where
   upd : List (Int, Int) -> List (Int, Int) -> { [RND] } Eff (List (Int, Int))
-  upd acc [] = return acc
+  upd acc [] = pure acc
   upd acc ((x, y) :: xs)
       = if (y > 479) then do
              x <- rndInt 0 639
@@ -38,7 +38,7 @@ updateStarfield = do xs <- Starfield :- get
              upd ((x, y+1) :: acc) xs
 
 drawStarfield : List (Int, Int) -> { [SDL_ON] } Eff ()
-drawStarfield [] = return ()
+drawStarfield [] = pure ()
 drawStarfield ((x, y) :: xs) = do line white x y x y
                                   drawStarfield xs