Common game patterns

While there are over 35 documented design patterns broken up over four subdomains of functionality, only a few of them are uniquely suited to game development. We'll spend a little time here briefly introducing them so that you get the hang of what we've been talking about so far:

• The Singleton pattern ensures that a given class only has one instance in a program, paired with one global access point (very useful for game manager classes). 
• The Observer pattern lays out a blueprint for notification systems, alerting subscribers to changes in behavior through events. We've seen this in action on a small scale with our delegate/event examples, but it can be expanded to cover much more ground.
• The State pattern allows an object to change its behavior based on what state it's in. This is extremely useful in creating smart enemies who appear to change tactics based on player actions or environmental conditions.
• The Object Pool pattern recycles...