Various pre-release cosmetic fixes

src/levels/l03.md

@@ -8,4 +8,7 @@ Third level is dictionaries. Each direction now leads to a feature with its own
     depth: 10
   straight:
     type: wall
-    depth:
+    depth:
+
+The rendered description ends with a hint reminding the player that each
+feature's name goes under a `type:` key (the property keeps its own name).