Tears of the Kingdom amazed developers all around the world when it released, with many developers rushing to twitter to speculate on how they achieved their physics-focused sandbox. Nintendo arrived in San Francisco to explain how they achieved their goals, with new insights into their physics and audio work. Today I’m going to round up all the best bits and interesting points raised by Nintendo, and how they achieved the technical marvel that is Zelda Tears of the Kingdom.

Nintendo conducted a presentation at GDC this week called ‘Tunes of the Kingdom: Evolving Physics and Sounds for The Legend of Zelda: Tears of the Kingdom’ with Senior Director Takuhiro Dohta, Sound Programmer Junya Osada, and Physics Programmer Takahiro Takayama taking to the stage to explain their work.

The developers explained that their philosophy behind both Breath of the Wild and Tears of the Kingdom was something called “multiplicative gameplay”. This is a concept where action and objects come together to create almost endless possibilities. The seeds of the ideas were started in Breath of the Wild, and the team started work on a DLC, which would go on to be Tears of the Kingdom. The team wanted to expand their work on “multiplicative gameplay” but allowing players to join multiple objects together. This would eventually be realised in Link’s Ultrahand ability, but it was a massive undertaking for Nintendo to get there.

“When I first saw the prototype, I was excited that this was going to be a great game, but this was going to be very, very difficult,” Takayama said. “I said to myself, ‘Are we really doing this?’”

The development team had a couple of goals with Tears of the Kingdom. They wanted to create an entirely physics-driven world, and wanted to create a system where unique interactions happened without any dedicated implementation – essentially, providing the building blocks to players, and unlocking their creativity.

Nintendo described early prototypes where they would throw a stone onto a cart and horse, and they would instantly fly into the air. Early work on Ultrahand was chaotic, with developers often proclaiming things like “I would hear things like, ‘It broke! It went flying!’ And I’d respond with, ‘I know! We’ll deal with it later!’”

One of the major challenges of creating an entirely physics-driven world was to remove all the non-phyiscs items, and turn EVERYTHING into being physics-driven. One example of this was a simple gate, which was not a physics-driven object in Breath of the Wild. Nintendo had to go back and change all the non-physics items, which now explains the long development and testing phase.

Even simply changes, like changing how a gate functions, led to unexpected effects for the development team. One of the great things about Tears of the Kingdom, is how there’s no real ‘right way’ to solve a puzzle, for example, shrines can be solved in many ways. Solving shrines in multiple ways was a microcosm of Tears of the Kingdom’s development, with developers finding all kinds of hidden solutions as they were developing and testing.

Ultrahand was fairly buggy in the first implementation, that’s when Takahiro Takayama looked back at an element of Breath of the Wild for guidance.

“The clash between these non-physics driven objects in Ultrahand with its high degree of freedom caused daily problems all over the land of Hyrule. We were in search of a solution. The key to that solution was in our experience developing Breath of the Wild. This is a cog wheel… that is not functioning properly due to non-physics-driven controls. We connected the two fixed cog wheels with a constraint to transfer velocity and moved one of them with a motor. Because all calculations are now physics-based, all the issues we were facing were now resolved. From this experience, we realized removing non-physics-driven objects and making everything physics-driven would lead us to the solution we were looking for.”

The development team was laser focused on these physics-based interactions, as they wanted to create a world full of items where players could create fun interactions. This included a system to make objects move, a system to make noises in a certain way and a system to create unique interactions. This was particularly apparent in the vehicles created in Tears of the Kingdom, where Nintendo created a system where wheels and a steering stick could be glued together with Ultrahand. Creating vehicles brought the whole team together, as complex items like Wagons were designed with a physics-first approach. Artists and designers were then brought in to layer on the graphics and textures, and it was all-important that the team were bought into the same vision to achieve what we see in the end product of Tears of the Kingdom.

Nintendo also gave us some insight into the sounds design for Tears of the Kingdom, which is as complex as the physics system. Junya Osada explained Hyrule contains voxel information to create a 3D environment, which are data points that store information about the terrain. For example, if Link is inside our outside then the audio can interact with the voxels, changing the audio if an object is behind a wall.

The audio design follows a similar pattern to the design philosophy for the rest of the game. Audio works without specific implementations, and abstract sounds can be combined to create new audio experiences. For example, there is no dedicated boat sound, the sounds are created by the objects moving through the water, with the audio changing based on the size, shape and materials used to build the vehicle. Osada said, “It’s making sounds that I have no memory of creating! Even the director told us, ‘This is basically a physics engine for sound, isn’t it?’”

Nintendo talking about their development of mainline Zelda series is always a highlight at GDC, and this was no different. The development team talked about the expansion of Hyrule, using Skyward Sword for a guide for Tears of the Kingdom’s Sky Islands and a Link to the Past’s Dark world as a guiding principle for The Depths.

Let me know what you think in the comments.