Platform Physics (0.14.0 Alpha)

The major addition for this release is physics support for platforms.  Now the various ball Actors will bounce and roll off of platforms, as well as blocks.  Actors flying upward, for whatever reason, should pass through them, but may be forcibly pushed upward as they pass the mid-point of the block's cell.

Additionally blocks and platforms now support having physics data set for them, such that friction and elasticity (restitution is the technical term used in the APIs, config file and mod XML files) can be set for them individually.

There are a number of more technical changes to Actor physics, many of which can be adjusted by editing the config file.   I also found and fixed some small bugs.