The Verge reckons Big Walk is pretty much co-op Breath of the Wild

When House House, the studio behind the mischievous and mechanically brilliant Untitled Goose Game, announced Big Walk as a cooperative open-world adventure launching August 4th on Nintendo Switch 2, PS5. And Steam, my mind didn't go straight to the art style or the promise of "co-op Breath of the Wild. " Instead, I fixated on the networking: what does it take to build a shared, physics‑driven sandbox where two players can organically wander, solve environmental puzzles,? And tug at the same virtual rope without the whole simulation tearing apart at the seams? Big Walk is an ambitious systems‑engineering statement dressed up as a playful exploration game. And its release gives us a perfect case study in the challenges of soft‑real‑time multiplayer coordination for large, interactive worlds.

Big Walk reimagines Breath of the Wild as a seamless co-op experience - and behind the scenes, its distributed state synchronization is a masterclass in soft real‑time game networking.

In production environments, we've seen how state reconciliation in a simple turn‑based mobile app can become a bottleneck. Scale that up to a lush island filled with dynamic objects - simulated physics, and two unsupervised clients. And the engineering decisions multiply. House House is known for crafting systemic interaction loops where seemingly everything is a toy. Now those toys must be shared over the internet. This article unpacks the likely technical architecture underpinning Big Walk, from its choice of network topology to how it might handle concurrent physics manipulation, all through the lens of senior engineering practice. Whether you're building a multiplayer game, a collaborative editing tool, or any distributed application where users directly manipulate shared world state, Big Walk's design constraints are instructive.

Why a Co-op Open World Is a Distributed Systems Nightmare

The classic Breath of the Wild is a single‑player game. Which means every falling tree, rolling boulder. And glider physics calculation happens on one deterministic timeline. Adding a second player - and perhaps no dedicated server - explodes the state space. Suddenly, you have two sources of truth, each with its own version of where a boulder is or whether a campfire is lit. The core problem becomes one of state authority and consensus: who is allowed to modify which objects,? And how do all participants eventually agree on the outcome?

From a systems perspective, this isn't unlike the challenges faced by collaborative document editing platforms such as Google Docs, only with much tighter latency budgets. In Big Walk, if one player pushes a log off a cliff and the other tries to step onto it at the same moment, the game must resolve that conflict within a single frame - typically 16ms at 60fps - without visible jitter or teleportation. Even a well‑known rollback netcode approach (like GGPO for fighting games) doesn't cleanly apply because the world state is far larger than a handful of character positions and you can't easily roll back physics interactions that propagate through the scene.

House House's previous title, Untitled Goose Game, sidestepped this entirely by being a local, same‑screen experience. The physics were deterministic (Unity's PhysX engine), so a split‑screen update just duplicated the input stream. Big Walk's online requirement - especially on the Switch 2. Where mobile hotspot play is plausible - means they had to design for intermittent connectivity and variable latency from day one. Their solution, whatever it turned out to be, has direct parallels to building resilient mobile‑first applications that synchronize complex domain models across unreliable networks.

How Big Walk's Systemic Interactions Differ from Scripted Multiplayer

Many co‑op games rely on scripted sequences: a door opens when both players stand on pressure plates, enemies aggro based on proximity. And world changes are pre‑authored. Big Walk promises an emergent, systemic sandbox - much like the physics‑driven playground of Breath of the Wild. In such an environment, a puzzle isn't a predefined lock‑and‑key; it's an arrangement of physical objects, chemical interactions. And environmental triggers that can be solved in unexpected ways. This is where the engineering gets fascinating.

Systemic design means that interactions are defined by rules, not by if‑statements. For example, fire spreads to dry grass, updrafts lift gliders, and metal objects attract lightning. When two players can independently, simultaneously. And asynchronously start a fire - cut grass. Or throw a metal shield into a storm, the game must evaluate all those rule sets on a shared authoritative timeline. If it's fully server‑authoritative, every action must be validated and rebroadcast. If it's peer‑to‑peer with a host or distributed ownership, you need robust object‑authority transfer and conflict resolution - much like optimistic concurrency control in a distributed database.

I suspect Big Walk adopts a model where the "host" player's machine acts as the primary physics authority, similar to how Valheim or Astroneer handle co‑op. This minimizes server costs and keeps latency low for the host. But it introduces the well‑known host‑advantage problem and requires careful interpolation and input prediction on the guest client. The inclusion of Nintendo Switch 2 suggests that even a mobile‑class ARM processor can serve as host, which means the computational budget for network serialization and physics must be tightly controlled - an impressive engineering feat in itself.

Networking Models: Authoritative Server vs. Peer‑to‑Peer for Casual Co‑op

Game networking architectures generally fall into two camps: dedicated authoritative server (DAS) and peer‑to‑peer (P2P). DAS offers strong anti‑cheat enforcement and consistent state, but it requires ongoing cloud infrastructure and introduces an extra network hop. P2P, often with a host migration mechanism, is cheaper and easier for small studios, but it opens the door to desynchronization and cheating. With Big Walk launching on three platforms including cross‑play, the networking model becomes a strategic choice that shapes the entire development process.

House House is a small team; maintaining a 24/7 fleet of authoritative servers across global regions for what is fundamentally a two‑player experience isn't the obvious first choice. More likely, they've used a relay‑based P2P approach with one client as an authoritative host. This is how many Unity‑based cooperative games operate: the host runs the full simulation. And the guest sends input commands while the host sends back world state snapshots. Unity's Netcode for GameObjects documentation explicitly supports this pattern with its NetworkBehaviour authority model, allowing developers to designate which peer owns an object's physics.

On the console side, Nintendo and Sony platforms traditionally require network traffic to pass through their respective matchmaking and relay services. Nintendo's NEX (now NSOP) and Sony's PlayFab‑based infrastructure can host lobby services and NAT punchthrough. But game state synchronization is still the developer's responsibility. So House House likely built a lightweight state‑replication layer on top of UDP, possibly with sequenced reliable messages for critical events like puzzle completion. This is where frameworks like Photon Bolt or Mirror would shine - they handle tick‑based synchronization and lag compensation out of the box, dramatically reducing the complexity of a project like Big Walk.

Synchronizing Dynamic Physics and Environmental Puzzles Over the Wire

Physics networking is notoriously difficult because rigidbodies continuously move Under the influence of forces, collisions, and joints. A naïve state‑sync approach - sending position and velocity every frame - can consume enormous bandwidth. Big Walk's serene island likely contains hundreds of physics‑active objects: crates, logs, puzzle mechanisms, and the players' own backpacks. Each of those objects must appear in roughly the same place on both screens. Or the cooperative fantasy breaks immediately.

One proven technique is to run a deterministic physics engine on both clients and only send input events. If both clients start from identical initial state and receive identical player inputs (with network‑assigned timestamps), their simulations will, in theory, diverge imperceptibly. Unity's PhysX can be made deterministic if floating‑point modes are controlled, but achieving cross‑platform determinism (between x86, ARM on Switch 2. And PlayStation's custom CPU) is a significant low‑level challenge. House House might instead use a state‑sync model with periodic snapshots and client‑side interpolation, similar to what Unreal Engine's built‑in networking provides.

Given the game's relaxed pace, snapshots could be sent at 10-15 Hz on a typical broadband connection, with dead reckoning and smoothing to cover the gaps. For objects that a player is actively carrying (a crucial mechanic in co‑op exploration), the host could temporarily transfer authority to the holding client to ensure zero‑perceptible latency for the holder. While the other player sees a slightly smoothed version. This pattern - object‑ownership transfer with predictive ghosting - is a sophisticated but well‑understood concept in modern game networking, documented in detail by Valve's Source Multiplayer Networking documentation

AI and Emergent Behavior in a Multiplayer Sandbox

Breath of the Wild's world feels alive because its AI Agents - wildlife, enemies, NPCs - react to the player's actions and to the environment. In a co‑op setting, these agents must be aware of and react to two players simultaneously, often in ways that create spontaneous cooperative moments. A bear that spots one player might start moving toward them. But if the second player lights a fire nearby, the bear's AI should reassess its goal and perhaps flee, creating a dynamic scenario that neither player scripted.

Implementing this as a fully distributed AI system is overkill. The host will typically run all AI behaviours and broadcast the resulting states to the guest. To avoid dead‑air moments where the guest waits for the host's AI update, House House could employ a lightweight client‑side prediction for AI positions that the guest then corrects once new data arrives. Tools like Unity's Behavior Trees