add some en chapter.

Author: Tsiannian

02.3-Observer.md

@@ -1,2 +1,26 @@
 Decoupling Patterns
 ============================
+
+^title Decoupling Patterns
+
+Once you get the hang of a programming language, writing code to do what you
+want is actually pretty easy. What's hard is writing code that's easy to adapt
+when your requirements *change*. Rarely do we have the luxury of a perfect
+feature set before we've fired up our editor.
+
+A powerful tool we have for making change easier is *decoupling*. When we say
+two pieces of code are "decoupled", we mean a change in one usually doesn't
+require a change in the other. When you change some feature in your game, the
+fewer places in code you have to touch, the easier it is.
+
+[Components](component.html) decouple different domains in your game from each
+other within a single entity that has aspects of all of them. [Event
+Queues](event-queue.html) decouple two objects communicating with each other,
+both statically and *in time*. [Service Locators](service-locator.html) let
+code access a facility without being bound to the code that provides it.
+
+## The Patterns
+
+* [Component](component.html)
+* [Event Queue](event-queue.html)
+* [Service Locator](service-locator.html)

02.4-Prototype.md

@@ -914,7 +914,7 @@ on the ship this modification occurred.
     dirty flag to note which objects have had forces applied and need to have
     their physics resolved.
 
-*	物理引擎跟踪着那些物理在运动那些空闲。应为一个空闲的物理知道收到力的作用才会移动，他在受力
+ *  物理引擎跟踪着那些物理在运动那些空闲。应为一个空闲的物理知道收到力的作用才会移动，他在受力
     之前不需要处理。这个“是否在移动”是一个赃位，来标记那些物体收到了力的作用并需要计算他们的
     物理状态。