Try improve crash course

docs/tut/crash-course/6-root.md

@@ -2,9 +2,9 @@
 
 Any reactive scopes created, such as by `effect()`, must be done so within a
 "root" reactive scope. This is the main purpose of `mount()`, which you use
-once at the top level to create your app as shown in the first introduction.
+once at the top level to create your UI.
 
-This is so that when the app is unmounted, it can clean up any reactive scopes
+This is so that if you want to destroy your UI, it can stop any reactive scopes
 created within it, since reactive scopes track any reactive scopes created
 within them.
 
@@ -53,16 +53,22 @@ The reactive graph for the above example looks like so:
 
 graph
 
-subgraph root["mount"]
+subgraph root
     direction LR
     count --> effect
 end
 ```
 
-When the `mount` scope is destroyed, the `effect` scope will also be destroyed
-since it was created within it.
+When the root reactive scope created by `mount()` is destroyed, the `effect`
+scope will also be destroyed since it was created within it.
+
+This is important because you may have an effect that updates the property of a
+UI instance, meaning the effect is referencing and holding that instance in
+memory. The effect being destroyed will remove this reference, allowing the
+instance to be garbage collected.
 
 You don't need to worry about ensuring all your effects are created within a
 root scope, since you should be creating all your UI and corresponding effects
 within a top-level `mount()` call that puts all your UI together. So it is safe
 to assume that any effect you create will be created under this top level scope.
+Vide will prevent you from accidently doing otherwise anyways.