improve hints in Implication lvl 2. #45

Game/Levels/Implication/L02exact2.lean

@@ -11,9 +11,16 @@ use rewrites to fix things up."
 
 /-- Assuming $0+x=(0+y)+2$, we have $x=y+2$. -/
 Statement (x : ℕ) (h : 0 + x = 0 + y + 2) : x = y + 2 := by
-  Hint "Rewrite `zero_add` at `h` twice, to change `h` into the goal."
-  repeat rw [zero_add] at h
-  Hint "Now you could finish with `rw [h]` then `rfl`, but `exact h`
+  Hint "You can use `rw [zero_add] at h` to rewrite at `{h}` instead
+  of at the goal."
+  rw [zero_add] at h
+  Hint (hidden := true) "Do that again!
+
+  `rw [zero_add] at {h}` tries to fill in
+  the arguments to `zero_add` (finding `{x}`) then it replaces all occurences of
+  `0 + {x}` it finds. Therefor, it did not rewrite `0 + {y}`, yet."
+  rw [zero_add] at h
+  Hint "Now you could finish with `rw [{h}]` then `rfl`, but `exact {h}`
   does it in one line."
   exact h