Lots of work on docs.

doc/site/variables.markdown

@@ -3,36 +3,36 @@
 Variables are named slots for storing values. You can define a new variable in
 Wren using a `var` statement, like so:
 
-    :::wren
+    :::dart
     var a = 1 + 2
 
 This creates a new variable `a` in the current scope and initializes it with
 the result of the expression following the `=`. Once a variable has been
 defined, it can be accessed by name as you would expect.
 
-    :::wren
+    :::dart
     var animal = "Slow Loris"
-    io.write(animal) // prints "Slow Loris"
+    io.write(animal) // Prints "Slow Loris".
 
 ## Scope
 
 Wren has true block scope: a variable exists from the point where it is
 defined until the end of the block where that definition appears.
 
-    :::wren
+    :::dart
     {
-        io.write(a) // ERROR! a doesn't exist yet
+        io.write(a) // ERROR! a doesn't exist yet.
         var a = 123
         io.write(a) // "123"
     }
-    io.write(a) // ERROR! a doesn't exist anymore
+    io.write(a) // ERROR! a doesn't exist anymore.
 
 Variables defined at the top level of a script are *global*. All other variables
 are *local*. Declaring a variable in an inner scope with the same name as an
 outer one is called *shadowing* and is not an error (although it's not
 something you likely intend to do much).
 
-    :::wren
+    :::dart
     var a = "outer"
     {
         var a = "inner"
@@ -42,7 +42,7 @@ something you likely intend to do much).
 
 Declaring a variable with the same name in the *same* scope *is* an error.
 
-    :::wren
+    :::dart
     var a = "hi"
     var a = "again" // ERROR!
 
@@ -50,6 +50,7 @@ Declaring a variable with the same name in the *same* scope *is* an error.
 
 After a variable has been declared, you can assign to it using `=`:
 
+    :::dart
     var a = 123
     a = 234
 
@@ -60,7 +61,7 @@ doesn't roll with implicit variable definition.
 When used in a larger expression, an assignment expression evaluates to the
 assigned value.
 
-    :::wren
+    :::dart
     var a = "before"
     io.write(a = "after") // Prints "after".