How the team behind Zelda made physics feel like magic

The Legend of Zelda: Tears of the Kingdom is a phenomenal game, praised for being able to improve and iterate upon Breath of the Wild. In the weeks after the game’s release, it was written up with all sorts of breathless praise as people wondered how Nintendo managed to make a game that seemed to outstrip the technical capabilities of now seven-year-old Switch hardware.

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

During the talk, Takuhiro Dohta, the technical director of Tears of the Kingdom, explained that the game had two major driving principles: “a vast and seamless Hyrule” and “multiplicative gameplay.”

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

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

Dohta defined multiplicative gameplay as a system by which players combine actions and objects to create their own ways to play. The developers, Dohta explained, did not want to create fun through discretely designed moment-to-moment gameplay events, rather they wanted to create a system that “lets fun happen.”

The seeds of this “let fun happen” system first sprouted in Breath of the Wild and its Octo Balloons, a monster part that Link could attach to heavy objects to make them float in the air. For Tears of the Kingdom, the developers expanded on that idea to encompass sticking together all kinds of objects resulting in the Fuse and Ultrahand abilities — powers that let Link combine objects to build weapons, items, and structures.

But for multiplicative gameplay to truly work, every interactive object in Hyrule had to behave in specific and predictable ways. This required what Takahiro Takayama, Tears of the Kingdom’s physics programmer, described as “an entirely physics-driven world.”

One of the first problems that arose was the clash between what Takayama called physics-driven objects and rigid body objects. Rigid body objects are objects whose every property — mass, velocity, weight, and more — is specifically designed regardless of its appearance. Early in Tears of the Kingdom’s development, the various gear mechanisms in Hyrule were rigid body objects. Meanwhile, a physics-based object’s properties are governed by physics; the big metal boxes that litter the Sky Islands above Hyrule are an example.

Takayama explained that though rigid body objects were easy to make, they created all kinds of problems when thrown into the mix with physics-driven objects. Like matter and antimatter, when a physics-driven object interacted with a rigid body object, the world broke. One example involved rigid body gears clipping through a metal box that had been inserted between them. The solution to this problem was simple. “Everything, without exception being physics-driven, is necessary to make multiplicative gameplay a reality,” Takayama said.

With everything being physics-driven, every interactive object in Hyrule would behave the way a player expects it to — the metal box now stops the gears from turning.

Hyrule then becomes “a world where players can express their creativity without [fear of] breakdown,” Takayama said. “A world where anything can happen depending on the player’s imagination.”

Takayama said making everything physics driven eliminated the need for what he called “dedicated implementation.” This would involve creating a program for every function and interaction. Without a physics-driven system, Link’s every action would require its own bespoke program to make it work.