sample video of Killer Core game using BulletXNA
http://www.youtube.com/watch?v=uPpOkA-bu6c
Using ghost objects for :
Explosion Shockwaves
Water - simple bouyancy
Ice - changing friction
Fire - Taking damage
Gravity Lifts - for carrying the player around.
Rigid bodies for :
Player, monsters, weapons and so on.
Runs on pc and xbox
