We have discussed how NPC is added to a virtual world. The NPCs appear in the virtual world with different purposes. Some of them tell stories or information whereas some of them serve players such as item trading.

We discussed how players interact with the NPCs. They can chat or trade with them. We compared several methods to chat with the NPCs. Every conversation system has its advantages and disadvantages, and we need to choose a right one for our virtual world. We can even mix their mechanisms together to supplement the system.

Also, we learned an advanced technique of mixing Java classes into the ActionScript server-side extension. This technique improves the performance in critical parts of the code and provide more possibilities to the extensions.

In the next chapter, we will discuss how to challenge our players by design quests in the virtual world.