World Labs' ICARE Runs a Full 3D Browser Game on 100 Million Splats

ICARE is not a product launch. It is a proof of concept built by a small team of artists and engineers to show what World Labs' full creative stack can actually do when pushed to its limits. The project was created in collaboration with WithLoreCo and the World Labs team, with art and animation by @LoicPix, world and UI design by @itsnicholash, and technical art direction and engineering by @PendingReallity. The result is a cinematic, browser-playable 3D adventure that runs entirely in your browser tab, no install required.

What you are actually playing

You play as Icarus in a cinematic 3D browser game, talking to dreamers, collecting artifacts, restoring worlds, and recovering lost feathers. Each world is inspired by a historical visionary: Da Vinci, Tesla, Hokusai, Frida Kahlo, and others. The experience is built for the power of a desktop or laptop, and is available now at icare-game.world, free to play.

What makes this more than a creative experiment is the technology underneath it. The team built ICARE using three components from World Labs' stack working together for the first time in a single shipped experience:

• Marble , the world generation model that produces explorable 3D environments from text or image prompts
• Spark 2.0 , the open-source renderer that streams those environments into a browser at interactive frame rates
• .RAD , a new streamable file format that makes progressive loading of massive splat scenes possible

The pipeline behind the worlds

To understand why this is technically interesting, you need to know what Gaussian splatting is. Instead of representing 3D scenes with triangles, 3D Gaussian Splatting takes photos of a scene and generates millions of semi-transparent, colored ellipsoids called splats, each containing position, size, orientation, color, and opacity, which blend together using Gaussian curves to render highly realistic material details. The problem is scale: World Labs is generating worlds that can be composed into huge labyrinths, but most consumer devices can only render 1–5 million splats at interactive frame rates, and large scenes need to download 100 MB or even 1+ GB of data before displaying anything.

Spark 2.0 solves this with three interlocking systems:

1. Continuous Level-of-Detail (LoD): Spark 2.0 builds a continuous LoD system around an LoD splat tree, where every splat is a leaf node in a hierarchy and each parent is a merged, lower-resolution version of its children. Rather than swapping between discrete resolution levels (which causes visible popping), Spark computes a "slice" through the tree that picks the best set of splats for the current viewpoint within a fixed budget.
2. Progressive streaming with .RAD: A newly designed .RAD file format enables random access and progressive transmission. On scene load, a rough 64,000-splat outline appears immediately, followed by incremental detail loading prioritized by viewpoint. As the user moves, priority is dynamically re-ordered.
3. GPU virtual memory: A fixed memory pool of 16 million splats is allocated on the GPU, with data swapped in and out in 64,000-splat pages , similar to virtual memory in operating systems , allowing limited GPU memory to access nearly unlimited scene data.

The LoD traversal itself runs in Rust compiled to WebAssembly, operating in a background Web Worker so LoD updates never block the render loop. Built on THREE.js and WebGL2, Spark 2.0 supports rendering over 100 million Gaussian points in any browser.

The launch video was the game

One behind-the-scenes detail worth highlighting: the team did not render the launch video separately. They connected Blender directly to the live Spark 2.0 runtime, animating cameras and previewing the splat-rendered result in real time. The same Marble-generated gameplay worlds that players explore in ICARE were used to create the trailer. There is no pre-baked cinematic , what you see in the video is the actual game running.

World Labs also noted that a deeper technical breakdown is coming later this week, covering world generation workflows, browser-native splat streaming, gameplay and interaction systems, and AI-assisted production.

The bigger picture

ICARE sits in a growing pattern of third-party and collaborative projects built on the Marble and Spark stack. Developers have already used Spark 2.0 for diverse experiments, including independent developer James C. Kane, who used it to create a multiplayer spaceship shooter called Starspeed, where the entire game scene is built from over 100 million splats and loaded entirely via browser streaming. Users can generate 3D worlds with text or images via Marble, stitch scenes together using Marble Studio, and render them into easily shareable web experiences via Spark , a complete creation-to-delivery pipeline.

Spark remains open source and MIT-licensed. The build-lod CLI tool converts any 3DGS file into a streamable .RAD with a precomputed LoD tree, or you can generate the tree on-demand in the browser. If you want to build something similar, the Spark documentation and Marble are both publicly accessible today. ICARE is the most complete public demonstration yet of what that stack can produce when a skilled creative team drives it.