Physics simulation that becomes a finished video

Tune the parameters, watch the simulation live and export an MP4 with synced audio. What you see in the preview is exactly the file you get.

Open the editor

Free, no account, nothing to install.

Animated illustration of the editor interface — tap the stage to push the ball. Open the editor to see the real simulation.

See the format in motion

Every seed is a whole variation of the scene. Cycle variations here, then open the one you like in the editor — the catalog has 17 scenes, all free.

Illustrative animations drawn live in your browser — tap one to push the balls around. The real physics engine runs in the editor.

Three steps, no uploads

  1. 01

    Pick the scene and the seed

    Every seed is a whole variation of the simulation. The search evaluates dozens in the background and shows which ones end well.

  2. 02

    Tune it while it runs

    Changing a parameter re-simulates from the start, and the first new frame shows up in under 150 ms.

  3. 03

    Export the MP4

    WebCodecs encodes faster than real time, with a soundtrack derived from the collisions.

Enough to publish, and nothing more

  • Preview identical to the file

    Preview and export call the same simulation and drawing functions. That equality is checked frame by frame, with zero pixel tolerance.

  • The ball plays your song

    Upload a MIDI and every bounce plays the melody's next note. The rhythm arena pulses on the song's own grid.

  • Deterministic audio

    Every collision becomes a note in the chosen scale, synced to the impact that produced it.

  • Export without a server

    WebCodecs encodes in your browser. Unlimited, with a discreet watermark.

  • Server-side render

    When the browser cannot encode — or you want it without a watermark — the same recipe runs in an isolated lane and returns the same file.

  • Seed curation

    Simulates without drawing, scores the outcome and ranks the candidates. Never spends credit.

  • Themes and overlays

    Six palettes in the recipe and, inside the video, a title, timer, counters, exit-order ranking and progress bar.

The same seed produces the same video on any machine

On every change, the project compares the simulation state after 2,000 steps against recorded vectors — in Chromium, Firefox, WebKit and Node. If one hash diverges, the merge does not happen.

That is what makes “the preview is the file” a structural property rather than a synchronisation effort.

Determinism vectors
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Reference vectors for engine 1.5.0, after 2,000 steps.

Preview and export are free and unlimited

The render happens on your computer — so it costs us nothing, and we do not need to charge for it. An account is only needed to save projects and for the paid features.

Start without an accountSee pricing