There’s a bridge to cross the lava pit in The Legend of Zelda: Tears of the Kingdom’s Marakuguc Shrine, but it’s broken. More than half of the bridge is piled on top of itself on one side of the pit, and a segment is clipped off on the other. For crossing the lava, the bridge is the obvious choice, but how can it be fixed?
After Tears of the Kingdom was released, a clip showing one possible solution went viral on Twitter: Link uses his Ultrahand ability to unfurl the stacked bridge by attaching it to a wheeled platform in the lava. The wheeled platform, now attached to the bridge’s edge, activates and moves forward, pulling the bridge taut and splashing lava as it goes, until the suspension bridge is suspended and can be crossed. In spite of this, the clip had game developers’ jaws on the ground, in awe of how Nintendo’s team manipulated the game’s physics system.
It’s simply a bridge to players, but it’s a miracle to game developers.
The most difficult part of game development is when different systems and features interact with each other, said Shayna Moon, a technical producer who worked on the 2018 God of War reboot and its sequel, God of War: Ragnarök. I’m really impressed by it. There are so many different kinds of solutions to this puzzle in particular because of the dynamic objects. There are so many ways this could go wrong.”
A segment of the bridge that operates independently was pointed out by Moon. Additionally, Link’s Ultrahand ability allows him to tie all of these things together – even the bridge – using the lava and the cart.
Nintendo reportedly spent a full year polishing Tears of the Kingdom. Every single member of the team contributed to the variety of options available, especially the QA testers, Moon said. “Open-world games like this with a lot of real-time physics objects are notoriously hard to QA test.”
In 2020, The Last of Us Part 2 included a rope that was necessary for solving a puzzle in physics-based shock and awe from game developers. As with Tears of the Kingdom’s bridge, players expected the rope to work, but developers knew how much work went into its design.
Luna Nielsen, a software engineer who goes by Luna the Foxgirl online and livestreams about the complexities of game engines, says the bridge has a lot of different points pulling on each other. It gets pretty mathy. It can get really funky when something pulls too much, and the bridge is suddenly inside of itself. Therefore, it must push it out. One thing has moved too far back. As a result, [the pieces of the bridge] begin to move independently of each other.”
Cole Wardell explained it this way: “When you grab the end of a lava bridge, a section is pulled to the side.” That drags the other attached piece a little bit, and that moves the next piece, and so on.” The pieces have to be nudged or slid back into places that don’t collide, which moves the pieces next to it, which moves the pieces next to it.”
The rope in The Last of Us Part 2 was the last time I saw something this impressive physics-wise/gameplay-wise. Aadit Doshi, Rocksteady Games’ senior gameplay and combat programmer, said the rope only appeared in a few very controlled scenarios. It is awe-inspiring to be able to confidently present the player with a stack of blocks connected by chains that move accurately without clipping, without objects shaking like crazy as they try to figure out what they need to do.”
Another viral clip from Tears of the Kingdom showed a door opening using four wheels and a chain. Taking shortcuts isn’t an option, Wardell told Polygon. “Physics engines take many shortcuts and make a lot of assumptions, both to optimize and to keep developers from pulling out their hair,” Wardell said. Almost all of these shortcuts, whether it be collision-free ropes [or] rotating objects only applying forces in specific ways, would make this kind of mechanism flat-out not work, or have the chain vibrate until it vanishes from view in a single frame, or some other infamous physics glitch.”
These problems are the reason why rope bugs “vibrate out of control.” If you don’t do everything just right, one movement will cause the other parts to move, which will cause more collisions – you don’t want the rope colliding with itself! Collisions cause more nudges, which results in more movement, resulting in your robe vibrating out of the map.”
Although complex physics are common in games, Doshi explained that Tears of the Kingdom pushes the limits of its engine to create exceptional gameplay and puzzles. “Realistic physics simulations take hours to calculate to make sure they are highly accurate and precise,” he said. “Game physics must produce similar results every 16-32 milliseconds (60-30 frames per second).”
Doshi said some games are able to avoid these complexities by designing around them. It restricts player action, which is the opposite of Tears of the Kingdom’s design. The game has constraints, but somehow, everything seems possible in this game.
Josh Caratelli, Gravity Well’s senior engineer and former Call of Duty developer, told Polygon that in game development, physics will break down when they least expect it. So there’s a whole Reddit page about physics goofs – player characters ragdolling into oblivion or enemies bouncing off walls. Games with physics bugs or glitches aren’t poorly made; it’s just that things can go wrong very easily.
Tears of the Kingdom’s physics aren’t magic, however – Nintendo clearly understands how physics interact in the game. Caratelli said what is most impressive is how stable it is and how it all works so there is no preprogrammed solution and players can solve puzzles at their own pace.
It’s not that other studios can’t achieve this level of technical innovation, but that they don’t prioritize the resources needed to do so. Often, that means supporting the humans who make the games we play. A large portion of the same team worked on Tears of the Kingdom, which appears to have been built on top of Breath of the Wild.
We don’t value institutional knowledge in the games industry, Moon said. Companies will prefer to hire someone from outside rather than train their junior or mid-level developers. By not valuing that institutional knowledge, we are shooting ourselves in the foot. Tears of the Kingdom really demonstrates this. Breath of the Wild was an advancement of that.”
It’s increasingly common for game developers to feel like they’re holding something together with duct tape, figuratively speaking, after the original designer was laid off or left; it takes a lot of time to reconfigure and assess how something was done. QA testers at Nintendo of America spoke out about a “frat house” experience at the company’s Washington headquarters last year. It appears, however, that the company values the expertise of its developers.
In addition to the overall hard work of the team, the institutional knowledge clearly played a role in making the process go so smoothly,” Moon said. The more stable and happy people are, the more likely they are to create quality games. You have to care about the people making games if you want good ones.”
