When Alan Willard walks the audience through the demo—complete with armored demon, dancing sparks, and rolling balls of light—the room falls still. Then the twist: Willard reveals that both the cinematic scene and the following tech demo haven’t been running off a game file but in real time from within UE4′s game editor. It’s like finding out that the actors on TV are actually tiny people living inside your set. It also helps him show that changes can be made to the game’s design and code, recompiled and executed nearly instantly—a technical feat that has been simply unheard-of in game development. And just like that, the silence in the room becomes reverent. The videogame industry has changed.