Thoughts on Super Mario World 2: Yoshi's Island - 3D Game Design Principles in 2D with Super FX 2

• Developer: Nintendo EAD
• Directors: Takashi Tezuka, Toshihiko Nakago, Shigefumi Hino, Hideki Konno
• Original Release: 1995-08 (JP), 1995-10 (NA, EU)
• Version Notes: This post refers to the original North American SNES release played on a Windows 7 PC via the bsnes emulator (64-bit version 088; new releases use the name "higan"). Xbox360 controller mapped as closely to the SNES controller as possible was used. No video filters used. "Blur" video shader, Direct3D, DirectSound, and RawInput were used.

By the time Super Mario World 2: Yoshi's Island was released for the Super Nintendo Entertainment System (SNES)  to Western markets in October, 1995, both the Sega Saturn and the Sony Playstation (as well as the minor players, the 3DO and Atari Jaguar) had already ushered in the fifth generation of home consoles. With the new generation came the dominance of 3D polygonal games on home consoles, supplanting the sprite-based 2D games that had previously dominated the market. Development of games that use these polygonal 3D spaces is fundamentally different from 2D sprite-based development in many ways. In this post, I will focus on the increased importance of graphical asset deformation as a mode of animation, in contrast to the more frame-based animation of many 2D games of the SNES era. Yoshi's Island, perhaps influenced by the growing 3D development market, implements many of these deformative techniques in its game design, making it one of the most experimental 2D, Nintendo platformers on the SNES. The function of these aspects of its design are likely major aspects of the game's critical success.

Most platformers, and indeed most games, on the SNES achieved animation by moving 2D sprite images relative to each other. Each of these sprites could have multiple frames of animation itself, with the color and location of each pixel in each frame rigidly defined. This approach was prevalent partially due to the SNES hardware, which was practically incapable of rendering complex 3D worlds or even of rotating, scaling, or deforming 2D sprites in-game.  The few games that attempted to do something differently usually had to do so through careful sprite-based trickery. Super Mario Kart (dev. Nintendo EAD, dirs. Tadashi Sugiyama & Hideki Konno, 1992), for example, used a clever combination of the Mode 7 (retrieved 2015-10-14) graphical mode and changing kart sprite size to give the impression of distance in a 3D world. Even the changing sprite size, however, was not done on-the-fly in the game; instead, the developers created the illusion of sprite scaling by swapping sprites of different sizes in and out of the display. (And even this false-3D world required an additional piece of hardware - the DSP-1 chip - on the game's cartridge.) These hardware constraints naturally informed the sorts of game design that could be accomplished on the SNES, and the restrictions imposed by such mostly-static, sprite-based design can be seen in the myriad 2D platformers released for the system. (There were exceptions of course: Clever software rendering on only the native SNES hardware allowed alternate approaches by a handful of games, such as Wolfenstein 3D [devs. id Software & Imagineer Co. Ltd., 1994], which managed a pseudo-3D first person shooter.)

In time, developers sought to expand the SNES's hardware capabilities by including additional processing power on the game cartridges themselves. Perhaps the most famous of these coprocessor chips were the Super FX and its successor, the Super FX 2. Nearly all of the games that used these Super FX coprocessors attempted to use the aging SNES to compete with the next generation of game consoles by creating games in 3D. However, these early attempts at 3D games on the SNES were simplistic; though they managed to capture some simple thrills of flight or racing, they could not explore the promise of 3D for game design in any real depth. Ultimately, these attempts at bringing 3D to the SNES were a dead end from a game design perspective. The one Super FX title that attempted something different with the additional power afforded by the Super FX 2 was Yoshi's Island. It deploys its coprocessor to expand the possibilities of 2D platforming, and as a result it ventured into more creative and experimental game design. The principles that it explores are ultimately closer relatives of later 3D game design than any of its 3D Super FX cousins.

Yoshi's Island is superficially quite similar to its predecessors in the Mario series. Its most obvious departures - the crayon-like art style and the Yoshi-protecting-Mario mechanic - have been amply discussed elsewhere, so I won't dwell on them here. Instead, let's consider how the game leverages the capabilities of the Super FX 2. Throughout the levels, numerous obstacles - including a few polygonal ones - are maneuvered in interesting ways. However, I want to focus on how the design of boss battles has evolved in this game compared to its predecessors, and how those techniques relate to more modern game design perspectives.

A game that takes place in a 3D world has a vastly larger number of possible positions and movements for its assets and camera than one that takes place in a 2D world. This feature precludes any possibility of planning the graphics pixel-by-pixel, as had been done in many sprite-based 2D games. Instead, 3D graphical assets are defined and then deformed, such as into a walk cycle, before the resultant pixels are calculated and rendered to the screen. This approach accommodates a flexibility of design in which a greater variety of player actions can be accommodated. Despite taking place in 2D, many of the boss battles in Yoshi's Island take similar approaches, something that previous Mario games could not do owing to hardware limitations. Where past Mario bosses typically required the dodging of patterned obstacles while trying to jump on the boss's particular weak spot, Yoshi's Island's bosses create variety that encourages critical thinking and dynamic attack strategy while maintaining excitement through the combination of this diversity and stylized graphics. These boss battles control player movement and positioning dynamically by using very large sprites, they allow a diverse set of positions and angles from which the player can attack via deformations and rotations, and they heighten tension during the battles by creating depth via dynamic sprite scaling. Let's look at several examples.

Sluggy the Unshaven deforming
in response to an egg throw.

First, consider the mid-world boss of World 5, Sluggy the Unshaven.  Sluggy is a large, gelatinous creature (reminiscent, perhaps, of the Big Beanie boss previously seen in level 1-8) that fills the tunnel in which the battle takes place from top to bottom, creating a dangerous wall that the player cannot move beyond. In another lovely graphical trick that shapes this scene's structure, Sluggy is transparent and, as the player quickly discovers, houses a vulnerable heart in the center of the gelatinous mass. Initially, the game suggests no mode of attack, but the player cannot remain inactive for long, because the large, impassable, squirming image of Sluggy (not easily possible on native SNES hardware) is forcing the player to move slowly and tensely leftward toward a bottomless pit. Because the blob has no obvious way in which it can be jumped upon like the bosses of past games, the impending doom forces the player to desperately try alternate strategies. Upon throwing an egg at Sluggy, a solution is finally revealed: Sluggy both moves back slightly and, shockingly at the time of the games release, dynamically deforms in response to the egg. The player now realizes that the deformation can provide a way out of this predicatment, because the repeated use of thrown eggs can deform Sluggy into a shape with exposes his vulnerable heart.  The use of large, deformable sprites has created tension which prompts creative player action, which then in turn introduces a completely new game mechanic. Crucially, this attack strategy is subject to the player's creativity. Sluggy can be deformed in any direction from any location; there is no one fixed point of attack as would have been expected in earlier platformers or even many subsequent ones. It is this flexibility, enabled by the Super FX 2, that makes the battle so exciting and memorable.

Raphael the Raven's battle on a
planetesimal, made possible by liberal
use of sprite rotation.

Later in World 5, the player encounters Raphael the Raven in a battle seemingly pulled directly from Nintendo's future, when they sent Mario into space for Super Mario Galaxy (dev. Nintendo EAD Tokyo, dir. Yoshiaki Koizumi, 2007). Like that later Wii title, this battle is able to explore the movement of platforming from a different perspective by translating the jump mechanic to a scenario in which the gravitational field varies spatially. If the Mario series is a mediation on jumping, then this battle, like a musical piece playing with variations on its melodic theme, is an exploration of a variation on the series's movement theme. After the characters dramatically fly up to a moon-like object in an animated sequence achieved with rotation and scaling, the moon serves as the obstacle in a cat-and-mouse game. By clever rotation of the character sprites, their projectiles, and the background, the player must deploy their jumping and ground-pounding skills on the planetesimal, whose gravity always points toward the center of the screen.  Put another way, the developers have asked the player to execute their jumping in a coordinate transformation.  Despite taking place in 2D, the Mario games up to this point have always limited their movement controls and their strategic deployment to what is effectively a 1D space - left and right in Cartesian-like coordinates. The same is true in this battle, but the concept is made refreshing by moving to polar coordinates with the Super FX 2's rotation capabilities - the player still moves primarily in 1D, but now it is the azimuthal angle that the player manipulates.

Baby Bowser looming in the
background, inching forward.

I'll finish off my examples as the game itself finishes: with the final battle with a giant Baby Bowser. Here, Yoshi's Island engages in fairly direct emotional manipulation of the player using techniques analogous to the previous battle with Sluggy the Unshaven. In that earlier scene, the movement of a large sprite leftward created tension that spurred the player to action. Here, the enormous Baby Bowser sprite, perhaps the most dramatically shaded sprite in the game, is scaled up and down to give the illusion of depth into the background. He gradually moves toward the player (both the player-character and the screen itself), all the while destroying the ground upon which the player stands, creating the most tense battle yet. Again analogous to the battle with Sluggy and using the knowledge that the player gained in that battle, the only way to hold Bowser at bay is to throw eggs, this time into the screen, which are scaled and rotated rapidly to give the appropriate illusion of depth.


These battles, and others like them, set the tone of the game as a whole. Yoshi's Island encourages experimentation in strategy on the part of the player by continually subverting the player's expectations of what will be required of them in a Mario game. The game is only able to make this design work because it adopts the sprite-deformation techniques enabled by the Super FX 2 and perhaps informed by the burgeoning 3D game design industry. In this sense, Yoshi's Island is the first truly modern Mario game in game design sense, as it, for the first time, has full control of its graphical assets and can deploy them against its themes. The small segments inform the whole, exploring the mechanics in greater and more experimental depth that had been achieved before.

Despite the critical acclaim that Super Mario World 2: Yoshi's Island and its re-releases received, there has been little critical discussion of how it is mechanically distinct from its predecessors owing to its hardware. Indeed, the word "Yoshi" has never even been mentioned on Critical Distance (retrieved 2015-10-16), despite the game's enduring legacy, both in terms of the sequels it spawned and the impact it likely had on future Nintendo game designs. Instead, it has become lost in the sea of Mario games, and what few consumer-guide-oriented reviews exist for the title largely focus only on surface-level discussions of the presence of an infant Mario character and the crayon-styled graphical assets. Such neglect of any deeper criticism is a shame, because while some aspects of its level design had become run-of-the-mill by the time of its release, other aspects, such as those discussed here, were truly remarkable for their subtle innovations.