nng levels

server/nng/NNG/Levels/Function/Level_9.lean

@@ -10,11 +10,16 @@ open MyNat
 
 Introduction
 "
+I asked around on Zulip and apparently there is not a tactic for this, perhaps because
+this level is rather artificial. In world 6 we will see a variant of this example
+which can be solved by a tactic. It would be an interesting project to make a tactic
+which could solve this sort of level in Lean.
 
+You can of course work both forwards and backwards, or you could crack and draw a picture.
 "
 
 Statement
-""
+"Given a bunch of functions, we can define another one."
     (A B C D E F G H I J K L : Type)
     (f1 : A → B) (f2 : B → E) (f3 : E → D) (f4 : D → A) (f5 : E → F)
     (f6 : F → C) (f7 : B → C) (f8 : F → G) (f9 : G → J) (f10 : I → J)
@@ -32,5 +37,6 @@ Statement
 
 Conclusion
 "
-
+That's the end of Function World! Next it's Proposition world, and the tactics you've learnt in Function World are enough
+to solve all nine levels! In fact, the levels in Proposition world might look strangely familiar$\\ldots$.
 "