When the first woman enters the ship, you hear a "chirping" noise over and over again in the background. It's the exact sound one of the "pods" makes in 2001 A Space Odyssey makes when it's RADAR (or whatever it is) is searching.
Shot on and off in 28 days over the course of six months.
Almost this whole movie was filmed in a studio.
An earlier draft of the script took place in an old rundown apartment building.