Adds API docs to sprite Node and Node3D

examples/game/lib/node.dart

@@ -65,6 +65,9 @@ class Node {
 
   ActionController _actions;
 
+  /// The [ActionController] associated with this node.
+  ///
+  ///     myNode.actions.run(myAction);
   ActionController get actions {
     if (_actions == null) {
       _actions = new ActionController();
@@ -119,6 +122,9 @@ class Node {
     invalidateTransformMatrix();
   }
 
+  /// The skew along the x-axis of this node in degrees.
+  ///
+  ///     myNode.skewX = 45.0;
   double get skewX => _skewX;
 
   void set skewX (double skewX) {
@@ -127,6 +133,9 @@ class Node {
     invalidateTransformMatrix();
   }
 
+  /// The skew along the y-axis of this node in degrees.
+  ///
+  ///     myNode.skewY = 45.0;
   double get skewY => _skewY;
 
   void set skewY (double skewY) {
@@ -289,6 +298,9 @@ class Node {
     return _transformMatrix;
   }
 
+  /// Computes the transformation matrix of this node. This method can be
+  /// overriden if a custom matrix is required. There is usually no reason to
+  /// call this method directly.
   Matrix4 computeTransformMatrix() {
     double cx, sx, cy, sy;
 
@@ -326,6 +338,9 @@ class Node {
     return matrix;
   }
 
+  /// Invalidates the current transform matrix. If the [computeTransformMatrix]
+  /// method is overidden, this method should be called whenever a property
+  /// changes that affects the matrix.
   void invalidateTransformMatrix() {
     _transformMatrix = null;
     _invalidateToBoxTransformMatrix();

examples/game/lib/node3d.dart

 part of sprites;
 
+/// An node that transforms its children using a 3D perspective projection. This
+/// node type can be used to create 3D flips and other similar effects.
+///
+///     var myNode3D = new Node3D();
+///     myNode3D.rotationY = 45.0;
+///     myNode3D.addChild(new Sprite(myTexture));
 class Node3D extends Node {
 
   double _rotationX = 0.0;
 
+  /// The node's rotation around the x axis in degrees.
   double get rotationX => _rotationX;
 
   set rotationX(double rotationX) {
@@ -13,6 +20,7 @@ class Node3D extends Node {
 
   double _rotationY = 0.0;
 
+  /// The node's rotation around the y axis in degrees.
   double get rotationY => _rotationY;
 
   set rotationY(double rotationY) {
@@ -22,6 +30,7 @@ class Node3D extends Node {
 
   double _projectionDepth = 500.0;
 
+  /// The projection depth. Default value is 500.0.
   double get projectionDepth => _projectionDepth;
 
   set projectionDepth(double projectionDepth) {