All physics simulation is handled by Bullet.
Web site: http://www.impossiballs.com
Game video: http://www.youtube.com/watch?v=RrfwtvT9-tA
iTunes link: https://itunes.apple.com/us/app/impossi ... d972439447
Google Play: https://play.google.com/store/apps/deta ... alls&hl=en
For some of the game objects e.g. like the floor which contains holes, a custom collision shape was developed with a custom collision algorithm
For the Android version a port was developed in pure Java from the Bullet version 2.78. The port is a somewhat stripped version i.e. components that were not used in the game (e.g. Characters or Actions) were not ported.
A big thanks to the Bullet developers for a great physics library!