(Not) Game Genres, pt. 14: John Nesky's 2D Game Solid Boundary Types

Taxonomy of Virtual Spaces

In 2022, John Nesky (Feel Engineer on Journey (Thatgamecompany, 2012)) wrote a Twitter thread analyzing various stylistic choices a game artist may make when designing the boundaries of a 2-D game (like many 2-D platformer games). He preserved the thread as a Google document and in pdf format for easy reference.

2D Game Solid Boundary Types by John Nesky

Nesky's analysis of visual styles has some crossover with my current work in analyzing the spatial paradigms of many platformer games. Each example image (see illustration above) features Samus Aran from Super Metroid (Nintendo, 1994) in an environment constructed by Nesky according to these different stylistic techniques. His design study tends to focus on 2-D platformers, but he also shows how the techniques work for other types of games.

2D Game Solid Boundary Types

Nesky defines 10 different art styles used convey the "fourth wall" through which the player views the game environment. The world is often presented as if in an architectural cross-sectional view, using the game's plane of action as the cutting plane. The navigable area of the game's environment is clearly rendered, but the internal structure of that environment (inside the walls, floors, and ceilings) may be abstracted (surface layer), hidden (silhouette), or stylistically presented (wide open spaces).

1. Modular Blocks
2. Flat Façade
3. Jutting Floor
4. Surface Layer
5. Deep Shadows
6. Silhouette
7. Perspective
8. Fake Perspective
9. Wide Open Spaces
10. Thin Walls

Most of these styles are designed around the capabilities of tile-based environment graphics, like those seen in earlier game consoles like NES, SMS, SNES, and Genesis. These styles do not take foreground or background elements into consideration. They only focus on the environment along the game's plane of action.

Analyzing the Analysis

There are three types of projection methods here that line up with my Taxonomy of Virtual Spaces.

Modular Blocks by John Nesky

Orthographic (Modular Blocks, Flat Façade, Jutting Floor, Surface Layer, Deep Shadows, Silhouette, Wide Open Spaces, Thin Walls)

For my purposes of analyzing spatiality, most of the the styles here are different methods of orthographic projection. The examples above all use a side elevation projection for the environment. Styles like Wide Open Spaces and Jutting Floor do convey a small sense of depth, as if the floors or environmental elements break through space into a foreground layer. However, this projection method tends to convey to the viewer that this is a flat space.

Fake Perspective by John Nesky

Oblique (various) (Fake Perspective)

Nesky's Fake Perspective examples each show the receding lines of the game environment's ground plane (or in the case of The Legend of Zelda: A Link to the Past, the dungeon walls). There are several different projection techniques in these examples.

Yoshi's Island uses a vertical oblique projection, where the side face of the front "wall" is flatly rendered orthogonally and the receding lines of the floor plane are rendered vertically (compare to Yo! Noid on my previous post).

Two games use different oblique projections to render a naive perspective view and a sense of depth: Yoshi's Story (elevation oblique) and Link to the Past (planometric oblique). The receding oblique lines in Yoshi's Story are mirrored left and right, creating an illusion that the lines are converging towards the horizon line. Link to the Past similarly mirrors its oblique lines at the corners of the room to convey a similar illusion. These are not true perspective renderings, though they use some of the same visual cues of a perspective projection.

Nesky's own example is also naive perspective, but the receding lines of the short wall in front of the player avatar appears to be inverted naive perspective: the receding lines diverge into the background instead of converging.

Perspective by John Nesky

Perspectival (usually 1-point) (Perspective)

Curiously, Nesky's first example is a vertical oblique projection and is not truly perspectival at all. This is a paraline projection and receding lines do not coverge in the distance.

Nesky's other Perspective examples are presented in 1-point perspective. Metroid Dread and Link Between Worlds both use full 3-D environments with the camera perpendicular to the back wall (Metroid) or the floor (Zelda). Both games usually retain a fairly flat view of their environments to mirror the gameplay standards of earlier 2-D games in their respective series. Being fully 3-D environments, the camera is also free to tilt and pivot to more dramatic angles as needed, breaking into 2-point or 3-point perspective.

The other example is Contra III, a game I referenced in my previous post). This scene also uses 1-point perspective, although this Super Nintendo title uses a tiled background and no true 3-D models. Another Twitter user joined Nesky's thread and asked, "Why isn't the Contra III example here Fake Perspective?"

Contrast the receding lines of Contra III and Link to the Past environments

I responded to the question with the above altered screen shots and stated that one can trace the receding lines of the environment to see if they converge. Contra III's lines converge almost perfectly on the center of the screen. Each line is projected at a different angle. In contrast, Link to the Past uses a naive perspective technique with the receding lines of each corner of the environment projected obliquely at about 45° from the horizontal. This offers a convincing sense of depth and is fully in line with the art style of the original Legend of Zelda, but it is not a true 1-point perspective.

Odds and Ends

Nesky also gives several separate games as examples of specific uses of these techniques that I think are worth mentioning as they overlap with my research (especially since these are two of my favorite games).

The Legend of Zelda: A Link to the Past

Nesky notes that Link to the Past uses different projection methods for indoor and outdoor environments. He refers to outdoor projection as orthographic, which I define as orthogonal (a classic "top down" view as opposed to a direct overhead view). He does note the unusual fact that you can see the horizon from the pyramid, something that should be impossible from a planometric projection! This is another example where the conceptual image plane of the background is rendered differently from the environment (see here and here).

Horizontal oblique projection in Flashback

Nesky also notes that Flashback's projection is "angled sideways," or in what is called a horizontal oblique projection. As he states, "This visually preserves precise vertical distances while adding depth to the world. Door frames and platform railings are rendered in front of the avatar." There are many doors in Flashback and this aspect is important to making them look like doors instead of walls.

Conclusion

Nesky is not an expert on the technical details of different projection methods, and he fully admits that is the case. But this was never the point of his study. His study focuses on the specific stylistic choices that game artists use (especially those making tile-based "pixel art" games) to define that invisible fourth wall that is coplanar to the player's screen. He has created another method of defining and grouping games by their aesthetic choices rather than purely by technical or genre classifications and I applaud his work.