SunaBox

Paint matter. Set it on fire.
Then press rewind.

SunaBox is a physics sandbox in the spirit of the legendary OE-CAKE: 32 kinds of matter you paint straight into the world, machines that really run, fire that really spreads, and more.

It runs free in your browser, and because its engine is bit-exact, every recorded session can easily be replayed, rewound, saved, and shared with friends.

Play free in your browser Wishlist on Steam Meet the engine
Free in browser 32 materials Opens OE-CAKE .oec files Perfect replays Opens in one click, no install Coming to Steam

What you can do

Paint 32 kinds of matter

Water, gel, oil, mercury, acid, nitro, rice, rubber, wood, stone, metal, ice, lava, fire, smoke, steam and more. Every material behaves differently. Ice melts. Wood burns to ash. Steam condenses. Nitro does… what nitro does.

Build machines that run

Weld strokes into rigid bodies, pin them on axles, drive them with jets, stretch rubber into slingshots, or take the controls yourself. The arrow keys can drive what you paint.

Import anything

Drop in any PNG and it becomes matter.
Your drawing. Your logo. A photo of your cat. Rigid. Liquid. Flammable.
Whatever you choose.
Old OE-CAKE .oec scenes open too, preserved exactly.

Rewind time

The engine is bit-exact, so a session is a starting state plus your inputs, which means file sizes stay lightweight. Replay it, scrub it backwards, share it as a link that provably reproduces the same world, bit for bit.

Classic Mode

One toggle and the toolbar becomes OE-CAKE's, laid out exactly as you remember it. Same toolbar, same buttons, same order, same muscle memory, fifteen years later.

Built on SunaEngine

Every simulation in SunaBox runs on SunaEngine, our open-source deterministic physics engine. Curious how it works?
See it prove itself live: engine.sunabox.dev.

Exclusive to Steam

The browser version is the demo, and it stays free. It is the whole toy: every material, every tool, every render mode, and full replay export and import. What the Steam build removes is the ceiling, and what it adds is everywhere you want to take your scenes afterwards.

Free in browser
Particle ceiling
30,000
World resolution
1.8×
Runs in
any browser
SunaBox on Steam
Particle ceiling
131,071
World resolution
4×
Runs in
native app

The whole particle ceiling

131,071 bonded particles instead of 30,000. That is the engine's real limit rather than a sandbox clamp, and it is more than four times the room. Big machines. Whole cities of matter. The scene you had to keep deleting half of.

Full simulation resolution

4× worlds against the browser's 1.8×. More particles per world unit means finer detail in the same space: thinner sheets, smaller moving parts, water that reads as water instead of as beads.

Built for your machine

A native app for Windows, macOS and Linux, with a Steam Deck build. No browser tab between you and the GPU, no tab-switch stutter, and the throughput to keep tens of thousands of particles at a smooth frame rate.

Steam Workshop

Publish a replay and let it prove itself on someone else's machine, bit for bit. Browse, subscribe, vote. Because a session is a starting state plus your inputs, what you share is tiny and what they watch is exactly what you built.

Wishlist on Steam Full release November 2, 2026. Play the free demo now, in your browser.

The love letter

In 2007, Prometech released “OE-CAKE!”

It was supposed to be a technology demo… instead, it quietly became one of the internet's favorite physics toys. People kept building with it: trading scenes, discovering tricks, making tiny works of art. Even after development stopped, the community never really disappeared.

SunaBox began with a simple question:

“What would OE-CAKE look like if someone built it today?”

Everything that followed grew from that question.

SunaBox is our love letter to OE-CAKE! and to that community: a clean-room successor, rebuilt from scratch for the modern browser, that opens your old .oec files and honors what made the original feel alive, then keeps going where 2007 could not!

Built with love.
Shared freely.
Still making messes.