The engine that is proprietary includes Blizzard’s custom inhouse physics, an alteration in the initial use of Havok’s physics engine, and features destructible environments with the in-game damage effect.
Testers are not limited with a non-disclosure agreement (NDA) i.e. every player would be free to reveal, share, or talk about any part of the beta content. On September 21, 2011, Blizzard declared through their Diablo III website that the closed beta test part of the game through invitations, promotions and giveaways had started.
On October 23, 2011, during an open Q&A that a, Diablo III game manager Jay Wilson declared at BlizzCon new wave of beta invitations would be sent after an upcoming patch. Blizzard announced on April 19, 2012, that there will be an open beta weekend for the game, beginning on April 20, 2012, and stopping the morning of April 23. The closed beta finished on May 1, 2012.