# Port a Three.js game to Unity and keep the hand-tuned physics

> Moving a browser racing game to Unity for phones, the developer asked Claude Code which Asset Store engine to use. It read the code and advised using neither, then ported the 170 lines of drift physics line by line so the feel stayed the same. The port and a new UI took about two hours.

- URL: https://paperchasewebb.ai/bots/marketplace/items/port-a-three-js-game-to-unity-and-keep-the-hand-tuned-physics/
- Type: Agent use case pack
- Category: Games
- By: PaperChaseWebb
- Works with: Claude Code (named in the listing); Plain .md
- Price: Free USD
- Difficulty: Intermediate
- Setup time: 30 min
- Time to result: One working session
- Format: Markdown (.md) file, port-a-three-js-game-to-unity-and-keep-the-hand-tuned-physics.md
- Version: 1.0, updated 2026-10-26
- License: Personal and commercial use. Credit the original source when you share the workflow.

## What you end up with

Ask the agent to read your code before it picks a framework, and say what must not change (here, the driving feel).

## What you get

- A plain-language summary of the workflow
- A fill-in prompt template
- What to watch out for
- A link to the original source

## Who it is for

Builders who already use AI agents and want a proven workflow they can copy into their own project.

## Tools needed

- Claude Code: compared engines, ported the code and rebuilt the screens
- ChatGPT: first UI concept image
- Claude Design: turned the concept into a first UI draft
- Unity: target engine for iOS and Android
- You need: An AI coding agent or chat model
- You need: A small real task to try it on

Cost to run: Free with the agent plan you already use.

## How it works

1. **Name the part of your game whose feel must not change and point the ag.** Name the part of your game whose feel must not change and point the agent at it Expected: Done before you move to the next step.
2. **Ask the agent to compare candidate engines against that code before in.** Ask the agent to compare candidate engines against that code before installing anything Expected: Done before you move to the next step.
3. **Port the core logic first and test it side by side with the original.** Port the core logic first and test it side by side with the original Expected: Done before you move to the next step.
4. **Do the UI as a separate pass from a concept image.** Do the UI as a separate pass from a concept image Expected: Done before you move to the next step.
5. **Keep the old build so you can compare feel on the same input.** Keep the old build so you can compare feel on the same input Expected: Done before you move to the next step.

## Sample prompt: Workflow template (Claude Code, ChatGPT)

```
Apply this workflow to [your project]:
1. Name the part of your game whose feel must not change and point the agent at it
2. Ask the agent to compare candidate engines against that code before installing anything
3. Port the core logic first and test it side by side with the original
4. Do the UI as a separate pass from a concept image
5. Keep the old build so you can compare feel on the same input
Stop and ask me before anything irreversible: deploys, payments, sends or deletes.
```

Adapted by PaperChaseWebb. Not the original author's prompt.

## Free preview of port-a-three-js-game-to-unity-and-keep-the-hand-tuned-physics.md

````markdown
# Port a Three.js game to Unity and keep the hand-tuned physics

PaperChase agent use case (free feed entry), version 1.0. Source: [@froessell on X](https://x.com/froessell/status/2114310224391655453), 2026-10-25.

## What they did

The builder wanted Drift Lane on iOS and Android. They asked Claude Code to choose between two racing engines from the Unity Asset Store. After reading the existing code, it recommended skipping both, because the handling came from about 170 lines of tuned physics that neither engine would reproduce. It ported that code directly. For the UI, a ChatGPT concept image went to Claude Design for a first draft, then Claude Code rebuilt the screens in Unity.

## Worth knowing

Ask the agent to read your code before it picks a framework, and say what must not change (here, the driving feel). A direct port of a small, tuned core often beats adopting a big engine. The game is still in progress.
````

## Worth knowing

- Ask the agent to read your code before it picks a framework, and say what must not change (here, the driving feel). A direct port of a small, tuned core often beats adopting a big engine. The game is still in progress.
- Figures are as reported by the original author and were not re-measured by us.

## Questions

**Where does this come from?** A public post credited to @froessell on X. Source: https://x.com/froessell/status/2114310224391655453

**Is it free?** Yes. Feed entries are free to read and download.

## How to get it

Free sample. Download it directly at https://paperchasewebb.ai/bots/marketplace/items/port-a-three-js-game-to-unity-and-keep-the-hand-tuned-physics/, no signup.

Seller: PaperChaseWebb Inc., mgmt@paperchasewebb.com