Polish text in the "Instancing" section

None of the changes in this CL change the meaning or spirit of the
underlying text. Instead, my goal was to tidy up miscellaneous things,
like:

* Remove passive voice
* Tighten wording when possible
* Clean up misc grammar nits and other errors
* Relayout text to fill 80 columns in some cases

learning/step_by_step/instancing.rst

@@ -6,67 +6,64 @@ Instancing
 Rationale
 ---------
 
-Having a scene and throwing nodes into it might work for small projects,
-but as a project grows, more and more nodes are used and it can quickly
-become unmanageable. To solve this, Godot allows a project to be
-separated into several scenes. This, however, does not work the same way
-as in other game engines. In fact, it's quite different, so please do
-not skip this tutorial!
+Having a scene and throwing nodes into it might work for small projects, but as
+a project grows, you will naturally add more and more nodes and it can quickly
+become unmanageable. To solve this, Godot allows a project to be separated into
+several scenes. This, however, does not work the same way as in other game
+engines. In fact, it's quite different, so please do not skip this tutorial!
 
 To recap: A scene is a collection of nodes organized as a tree, where
 they can have only one single node as the tree root.
 
 .. image:: /img/tree.png
 
-In Godot, a scene can be created and saved to disk. As many scenes
-can be created and saved as desired.
+Recall that a scene can be created and saved to disk. You can create and save
+as many scenes as you desire.
 
 .. image:: /img/instancingpre.png
 
-Afterwards, while editing an existing or a new scene, other scenes can
-be instanced as part of it:
+Afterwards, while editing any scene, you can instance other scenes as part of
+it:
 
 .. image:: /img/instancing.png
 
-In the above picture, Scene B was added to Scene A as an instance. It
-may seem weird at first, but at the end of this tutorial it will make
-complete sense!
+In the above picture, Scene B was added to Scene A as an instance. It may seem
+weird at first, but by the end of this tutorial it should make complete sense.
 
 Instancing, step by step
 ------------------------
 
-To learn how to do instancing, let's start with downloading a sample
-project: :download:`instancing.zip </files/instancing.zip>`.
+To learn how to do instancing, let's start by downloading a sample project:
+:download:`instancing.zip </files/instancing.zip>`.
 
-Unzip this project in any place of your preference. Then, add this project to
+Unzip this project anywhere you like. Then, open Godot and add this project to
 the project manager using the 'Import' option:
 
 .. image:: /img/importproject.png
 
-Simply browse to inside the project location and open the "project.godot"
-file. The new project will appear on the list of projects. Edit the
-project by using the 'Edit' option.
+Simply browse to the folder you extracted and open the "project.godot" file you
+can find inside it. After doing this, the new project will appear on the list
+of projects. Edit the project by pressing the 'Edit' button.
 
-This project contains two scenes "ball.tscn" and "container.tscn". The
-ball scene is just a ball with physics, while container scene has a
-nicely shaped collision, so balls can be thrown in there.
+This project contains two scenes, "ball.tscn" and "container.tscn". The ball
+scene is just a ball with physics, while the container scene has a nicely
+shaped collision, so balls can be dropped in there.
 
 .. image:: /img/ballscene.png
 
 .. image:: /img/contscene.png
 
-Open the container scene, then select the root node:
+Open the container scene, and then select the root node:
 
 .. image:: /img/controot.png
 
-Afterwards, push the link shaped button, this is the instancing button!
+Afterwards, push the link shaped button. This is the instancing button!
 
 .. image:: /img/continst.png
 
-Select the ball scene (ball.tscn), the ball should appear at the origin
-(0,0), move it to the center
-
-of the scene, like this:
+Select the ball scene (ball.tscn). The ball should appear at the origin (0,0)
+which is at the top-left of the container scene. Drag the ball to the center of
+the scene, like this:
 
 .. image:: /img/continstanced.png
 
@@ -74,13 +71,14 @@ Press Play and Voila!
 
 .. image:: /img/playinst.png
 
-The instanced ball fell to the bottom of the pit.
+The instanced ball should fall somewhere to the bottom of the pit before coming
+to rest.
 
 A little more
 -------------
 
-There can be as many instances as desired in a scene, just try
-instancing more balls, or duplicating them (Ctrl-D or duplicate button):
+You can create as many instances as you desire within a scene. Just try instancing
+more balls or duplicating them (via Ctrl-D or the duplicate button):
 
 .. image:: /img/instmany.png
 
@@ -93,21 +91,22 @@ Cool, huh? This is how instancing works.
 Editing instances
 -----------------
 
-Select one of the many copies of the balls and go to the property
-editor. Let's make it bounce a lot more, so look for the Bounce
-parameter and set it to 1.0:
+Select one of the many copies of the balls and go to the property editor. Let's
+make it much more bouncy. To do this, look for the Bounce parameter and set it
+to 1.0:
 
 .. image:: /img/instedit.png
 
-Grey "revert" button will appear. When
-this button is present, it means we modified a property in the
-instanced scene to override a specific value in this instance. Even
-if that property is modified in the original scene, the custom value
-will always overwrite it. Pressing the revert button will restore the
-property to the original value that came from the scene.
+Notice that a grey "revert" button appeared. When this button is present, it
+means we modified a property in the instanced scene to override a specific
+value that differs from the original scene. Even if that property is modified
+in the original scene later, our custom value here will continue to overwrite
+it. Pressing the revert button will restore the property to the value that
+comes from the original scene.
 
 Conclusion
 ----------
 
 Instancing seems handy, but there is more to it than meets the eye!
-The next part of the instancing tutorial should cover the rest..
+The next part of the tutorial will show how this feature can help you organize
+your entire game...