Refactor.

doc/src/engine/compile.md

@@ -3,7 +3,7 @@ Compile a Script (to AST)
 
 {{#include ../links.md}}
 
-To repeatedly evaluate a script, _compile_ it first into an AST (abstract syntax tree) form:
+To repeatedly evaluate a script, _compile_ it first into an `AST` (abstract syntax tree) form:
 
 ```rust
 // Compile to an AST and store it for later evaluations

doc/src/engine/index.md

@@ -0,0 +1,8 @@
+Using the Engine
+================
+
+{{#include ../links.md}}
+
+Rhai's interpreter resides in the [`Engine`] type under the master `rhai` namespace.
+
+This section shows how to set up, configure and use this scripting engine.

doc/src/engine/optimize/reoptimize.md

@@ -4,13 +4,13 @@ Re-Optimize an AST
 {{#include ../../links.md}}
 
 Sometimes it is more efficient to store one single, large script with delimited code blocks guarded by
-constant variables.  This script is compiled once to an `AST`.
+constant variables.  This script is compiled once to an [`AST`].
 
-Then, depending on the execution environment, constants are passed into the [`Engine`] and the `AST`
+Then, depending on the execution environment, constants are passed into the [`Engine`] and the [`AST`]
 is _re_-optimized based on those constants via the `Engine::optimize_ast` method,
 effectively pruning out unused code sections.
 
-The final, optimized `AST` is then used for evaluations.
+The final, optimized [`AST`] is then used for evaluations.
 
 ```rust
 // Compile master script to AST