Update to reflect changes in Prelude

binary_tree.ld

@@ -3,18 +3,18 @@
 box states = []
 
 fn push! () -> {
-  update! (states, append (_, turtle_state ()))
+  update! (states, append (_, unbox (turtle_state)))
 }
 
 fn pop! () -> {
   let state = do states > unbox > last
   update! (states, butlast)
   penup! ()
-  load_turtle_state! (state)
+  loadstate! (state)
 }
 
 fn branch! () -> {
-  pc! (colors :olive)
+  pc! (colors :green)
   pw! (4)
   fd! (20)
 }