Answer: Parallel Projection
For over thirty years now, video game designers have used a rather clever trick to help create the illusion of 3D space. This trick, commonly referred to in the industry as “isometric graphics” but which is actually a form of parallel projection, predates 3D rendering engines and virtual reality gear by decades–the first use of it was in Sega’s 1982 arcade game Zaxxon.
What is parallel projection? It’s a type of graphical representation where the lines of projection that define the edges of objects are parallel both in reality and within the projection plane itself that is rendered on the screen. Video game designers took advantage of a subset of parallel projection wherein you skew the direction slightly to present all three axes (length, width, and height) to create an illusion of depth much like a photographer would change their position relative to a box to show the sides and shape of the box (rather than simply photograph it dead on where you could only see the width and height).
Image courtesy of FreeDesignFile.