Multiverse

One space repeating away into copies of itself. The repetition says there is no single version of this room, and no single version of the person standing in it.

Small differences between the copies are what keep it unsettling. Identical repeats read as a mirror. Copies that disagree read as separate worlds.

Build a corridor of rooms receding from the lens, each one framed by the last. A doorway, an arch or a window edge gives every layer a boundary.

Change something in every copy. The light shifts, the wardrobe changes, a chair moves, the subject stands somewhere else. One change per layer is enough to do it.

Depth of field falls away through the run, so the nearest copies are sharp and the far ones soften. That is what stops the frame reading as a flat pattern.

Use it for a choice, a memory, a dream layer, or a character meeting versions of themselves.

Skip it for a straightforward scene. The look announces itself and takes the scene with it.

Split Screen divides one frame with a hard line and plays two separate images at the same time. Neither image contains the other.

Multiverse nests instead. A dividing line across the frame is Split Screen. Rooms inside rooms receding away from the lens is Multiverse.

Christopher Nolan builds Inception (2010) on dream levels that sit inside each other, and the film keeps cutting between them so the audience has to track which layer it is in. Satoshi Kon does the same with dreams in Paprika (2006). David Cronenberg nests game worlds in eXistenZ (1999), until the characters can no longer say which level they are on.

Identical copies come back, which reads as a mirror tunnel instead of parallel worlds. Say each version differs slightly, and name one thing that changes.

The second failure is a single room. Ask for a corridor of parallel rooms receding, with every one framed by the room in front of it.