The ’90s was a decade of tremendous change for video games. 1992 birthed Ultima Underworld and Wolfenstein 3D, heralds of an oncoming wave that crashed ashore with 1993’s Doom. This wave brought the supremacy of 3D. During the ’80s, 3D was mostly the domain of roleplaying games, but by the end of the ’90s virtually all new mainstream video games were rendered in polygonal 3D.

This was more than just a graphical innovation. It was a revolution of perspective. The transition from two dimensions to three also marked a transition in the role of the player from observer to inhabitant. More important than 2D or 3D graphics is the 2D or 3D perspective. A 2D perspective places the player, the narrator, in a role of watching the game world from outside. A 3D perspective places the player inside the game world.

Let’s acknowledge for a moment that there are gray areas here. Final Fantasy Tactics‘s environment is rendered using 3D polygons, but the perspective is fundamentally 2D. The battlefield has variable height, but it is on the order of a contour map; the most important movement takes place on a plane, and the player looks down from above. Likewise, After Burner carries no pretenses of true 3D rendering, but its gameplay relies upon all three axes of movement. 3D gameplay is separate from 3D graphics.

But what is the essential nature of 3D gameplay? It is the placement of the player within the scene. 2D games provide an external view, typically as either the view of an omniscient eye in the sky or as a side-view cross section of the world. There is a clear division; the game world exists as a Flatland sequestered behind the monitor screen, and the player sits comfortably in the real world on the other side. But 3D is different.

In a game with 3D gameplay, the player embodies either a character in the game or a virtual camera existing in the game world. Either way, there is a definite position that the player, the narrator, occupies. Unlike 2D games, where the player is outside the world, the player is moored to the game world. She still views the game through the screen, true; however, there is no longer a comfortable division. The game world surrounds the player, and sits on all sides. Instead of an omniscient view, the player’s view is strictly limited. There are things above and behind the player, and no way to see them all at the same time.

This is the essential quality of 3D gameplay. The player is embedded in the game world, is embodied, and thus can be led, can be surprised, can be snuck up on. 2D gameplay constructs a diagram: it provides a representation of the game world, manageable and tidy. 3D gameplay presents architecture. It must be traversed and walked through.

This distinction was instinctively understood by the creators of Wizardry and Akalabeth, two of the earliest first-person computer roleplaying games. They allow players to not just map dungeons, but explore them. The player’s physicality within the game world serves to make concrete the action of information gathering. To reveal new areas in Rogue or Warcraft, one must move a character. To reveal new areas in System Shock, one must move the player.

In 2D games, the player is still easily capable of identifying with a character, and thus feeling the tension of entering a new area or the danger of being hemmed in. However, only 3D gameplay can surround the player on all sides. In 2D games, there is always one avenue of exit: out of the screen, into the real world and away. In 3D, however, the path through the screen doesn’t lead out, but only in, deeper into the player character or camera. Behind that body, that camera, is more of the word.

3D games are about place, about architecture. They are about floors and walls and ceilings, or about open voids, vulnerable from all sides. The third dimension is not height, but depth; it gives the player a way forward even as it robs her of her only sure avenue of retreat.