GameCrate writes:

The Medium is a game fascinated by the concept of duality; of events happening simultaneously in different places at the same time. This idea is featured heavily in the marketing, acts as a focal point of the gameplay, and is foundational to the story. Beyond the thematic focus of the game though, I kept feeling like this concept of bifurcation extended to the experience of playing the game as well.

Source: N4G PC Review: The Medium is a beautiful but shallow exploration of duality | GameCrate