It's time to design our own big-bang abstraction.

• World.java
• BigBang.java

Here's one application:

• Game.java
• Circle.java

Here's another:

• Ripples.java
• Circle.java (for Ripples)

And another one:

• Ripples.java (from Fri, with Chetan)
• Circle.java (the associated Circle class)

Notice how the core framework is one and the same throughout.