Sandbox

A shared falling-sand world in the browser. Everyone in it sees the same sand, water, fire, lava and plants, live, and what you leave behind stays for the next person.

What it is

One world of falling sand, in the style of Noita and Sandspiel. Pick a material and paint: sand piles, water finds its level, fire spreads to wood and burns out as smoke, gunpowder chains into explosions, and seeds grow into flowers. Open it in two browsers and a stroke in one appears in the other within about a second. Close the tab and come back tomorrow, and the world is still there, changed by whoever came in between.

What good means here

Good means a shared world that has enough mechanics to be interesting, and incentivises interaction between players. It should also technically be able to support simulating and rendering the shared world and real-time player interactions, within the compute constraints of the server.

What I read and looked at

• Noita (Nolla Games), whose every pixel is simulated, and the Noita wiki on world generation: what a falling-sand world can feel like, and how its caves are built.
• Max Bittker's Sandspiel, a falling-sand game in the browser whose players share what they make: proof that a browser can run a full cellular simulation, and a model of people building on each other's worlds.
• Sean Barrett's herringbone Wang tiles, the technique behind Noita's caves, which I compared against noise and tunnelling for my own generator.

What is enforced and what is judged

Enforced by checks that fail when the claim breaks:

• Identical worlds: the same inputs in Node, Chromium, Firefox, WebKit and native Rust must give bit-identical hashes. A deliberately broken build must be caught, which proves the check can fail.
• Real time and shared state: two clients join the running app, one paints, and both must agree on the world's hash once it lands (spec/).
• Persistence: the world survives a server restart and comes back at the same tick from its saved snapshot and input log.

Judged, by watching people use it: whether the materials feel right, and whether a shared world makes people play together or just alongside each other.

What I chose not to build

• A server-side simulation. The course machine has one shared CPU and 256 MB, too little to run the world for everyone; players' browsers are free compute.
• Accounts and chat. Painting needs no sign-in, and the shared world is the conversation: you answer someone by building on what they left.
• A reset button for players. A world that anyone can wipe isn't one that lasts. Only the admin can reset a world, behind a token.

Status

Live at comp4020-final-yarramoo.fly.dev. The front page is a generated cave world with players: walk, levitate and dig down through the caves, pick up spells (Push, Blast, Water, Rose, Fire bolt and Bomb), and fight. Death drops your spells as a bag anyone can take, and achievements are awarded for what you do. The shared painting sandbox is at /sandbox. Both persist across restarts. Still to come before the final submission: balance, polish, and a live soak test that reaches the deep caves.