Need to fix the rendering problem
implemented most of the addButton function.
Todo: createBlockInWorld() method in Block.java
Read more testbedTest and figure out more about the possible settings
Finished the drawing part when a customized shape is added to the
screen.
TODO: figure out how fixtures are attached to the body and how to use
different shapes and joints....
The createBlockInWorld() method has some math problem
Fixed a bug.
Todo: need to figure out why sometimes when you zoom in , the AABB
overlapping issue is not correctly checked. Maybe in somewhere of the
code, I am supposed to use float instead of int...
Start working on editing mode.
Todo: Start designing the new UI so Patrick can start making it
TODO: work on the edit mode