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How the team behind Zelda made physics magical

The Legend of Zelda: Tears of the Realm is a phenomenal game, praised for its ability to improve and repeat Breath of the Wild. In the weeks following the game’s release, it was raved about with all sorts of jaw-dropping praise, as people wondered how Nintendo managed to create a game that seemed to exceed the technical capabilities of the Switch hardware, aged seven.

To the developers, the game looked like magic. But during a talk at the Game Developers Conference 2024, Nintendo said it wasn’t magic but a distinct, well-executed development strategy that nonetheless felt magical.

During the conference, Takuhiro Dohta, the technical director of Tears of the Kingdomexplained that the game was based on two major guiding principles: “a vast and transparent Hyrule” and “multiplicative gameplay”.

The first was relatively simple. “We wanted players to see things in the distance and go there,” Dohta said. This philosophy was taken from Breath of the Wild, with the new challenge of seamlessly connecting sky, surface and subsurface. We can see how this integration worked in Tears of the Kingdom in Link’s free fall pose as he descends from the sky to the surface and again between the surface and underground. The action connects the three different worlds of Hyrule.

Connect free falls from sky to ground and from ground to underground.
Image: Nintendo

However, Dohta cautioned that creating a large, interconnected world doesn’t mean it will be inherently fun. The pleasure, he explains, comes from the second principle: multiplicative gameplay.

Dohta defined multiplicative gameplay as a system by which players combine actions and items to create their own ways of playing. The developers, Dohta explained, didn’t want to create fun through discretely designed moment-by-moment gameplay events, but instead wanted to create a system that “allows fun to happen.”

The seeds of this “let the fun happen” system germinated for the first time Breath of the Wild and his Octo Balloons, a monster part that Link could attach to heavy objects to make them float in the air. For Tears of the Kingdomthe developers expanded this idea to encompass sticking together all kinds of objects, which gave rise to the Fuse and Ultrahand abilities – powers that allow Link to combine objects to build weapons, items, and structures.

But for multiplicative gameplay to actually work, every interactive object in Hyrule had to behave in a specific, predictable way. This required what Takahiro Takayama, Tears of the KingdomThe Physics Programmer from , described as “a world entirely focused on physics”.

One of the first problems to emerge was the conflict between what Takayama called physics-driven objects and rigid-body objects. Rigid-body objects are objects whose every property (mass, speed, weight, etc.) is specifically designed regardless of its appearance. At first Tears of the KingdomDuring development, Hyrule’s various gear mechanisms were rigid-body objects. Meanwhile, the properties of a physics-based object are governed by physics; the large metal boxes that litter the sky islands above Hyrule are an example of this.

Takayama explained that while rigid-body objects were easy to make, they created all sorts of problems when mixed with physics-driven objects. Like matter and antimatter, when a physics-governed object interacts with a rigid-body object, the world collapses. One example involved rigid-body gears passing through a metal box inserted between them. The solution to this problem was simple. “Everything, without exception physics-based, is necessary to make multiplicative gameplay a reality,” Takayama said.

With everything being physics-based, every interactive object in Hyrule would behave as the player expects: the metal box now prevents the gears from turning.

Hyrule then becomes “a world where players can express their creativity without (fear of) failure,” Takayama said. “A world where anything can happen according to the player’s imagination.”

Takayama said the fact that everything was physics-based eliminated the need for what he called a “dedicated implementation.” This would involve creating a program for each function and interaction. Without a physics-based system, Link’s every action would require its own tailor-made program to work. If the developers want Link to drive a type of vehicle, they will need to create a dedicated program governing the vehicles.

Although making every object in Hyrule physics-based was a technical challenge, it alleviated the need to create so many dedicated programs throughout the development cycle.

“Instead of creating a vehicle program,” Takayama explained, “we created a system in which vehicles could be manufactured.”

There is no program for vehicles, but rather programs for manufacturing a vehicle.
Image: Nintendo

The distinction may seem subtle, but it is in this subtlety that all the “magic” of the Tears of the Kingdom laid. When the developers panicked Tears of the KingdomIn bridge physics, wondering how they programmed bridges to behave correctly without problems, the truth was that they had created systems governing each individual component of a bridge: its slats, its links and even the various forces like the wheels that would interact with it. Even the music in the game used this modular approach. Junya Osada, Tears of the KingdomThe sound designer of , explained that the game’s cart sounds did not come from his team taking out and recording a horse-drawn cart.

“There is no sound of a cart but the sound of squeaking wheels, chains and joints,” Osada said.

These systems facilitated the emergent types of gameplay that made Tears of the Kingdom such a special game. Players were able to use them in ways that the developers themselves would never have thought of.

An example of these systems at work is the modest Zonai wearable device. In Breath of the Wild, cooking was done in dedicated locations, but with the portable pot, Link could now cook anywhere. Because everything, including cooking ingredients, was physics-based, the developers faced a problem: If Link decided to cook on the mountainside, all of his ingredients would slip out of the pot.

With a dedicated implementation, the pot would simply cook no matter where it was placed and nothing else. However, the multiplicative gaming philosophy ensured that no matter where a pot was placed, the cooking surface would orient horizontally so your soup wouldn’t spill. This gave the pot a utility beyond cooking, allowing it to be used as a ball joint leading to all sorts of wacky creations.

from Nintendo Tears of the Kingdom The panel explained that the game’s success was driven by the idea that players should make their own fun, supported by a robust physics system that applied to every object in the game. But the speech highlighted another reason, tacit, which contributed to Tears of the Kingdom be on every shortlist for Game of the Year 2023: Nintendo keeps its talent.

In an industry where the average career length is measured in the single digits, each speaker has worked for Nintendo for at least 10 years. This type of retention is an important factor in Nintendo’s continued success. Institutional knowledge is preserved and teams can work together more easily with limited disruption from staff turnover. While Nintendo is by no means a perfect company, it seems to understand that the best way to get good games is to employ and retain good people.

“Working with game designers and artists who understood the vision,” Dohta said, “was essential to bringing this vast world to life.”

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