Most of the work was made in camera. There was no vfx for snow. The break of the wall and the hole in the floor were both in camera work (the hole in the floor was enhanced a bit by vfx). The ceiling hole was also real, along with the dust that it produced as the actor dropped. As two of the actors had to play two parts (in rather heavy make up), the schedule of shooting along with the camera locks were logistical nightmares. Everyone (except the boy and girl in the beginning) is an Egyptian super star, playing a role entirely outside of their comfort zone. Malek (the actor dropping from the ceiling), did his own stunt. In order to avoid cuts to move forward in the film’s timeline, the whole film was shot as if it is a real-time piece of theater.