Terms of Use
By using Physics Sandbox at physics.stacklis.com you agree to the terms below. They are intentionally short.
1. The product
Physics Sandbox is a 2D physics simulator with a paid "Pro" tier that unlocks scene saving and a printable derivations export. It is provided as a learning tool, not a research-grade engineering instrument. Numerical results are approximate and depend on browser performance.
2. License
You receive a personal, non-transferable license to use the app on your devices. The Pro unlock is tied to your browser's localStorage on each device; you may activate Pro on multiple personal devices using the same purchase, but you may not redistribute, resell, or pirate the unlock.
3. Pricing
Pro is a one-time payment of $9 USD. There is no subscription. Payment is processed by Stripe. We may change the price for new customers at any time; existing Pro users keep their unlock at no further cost.
4. Refunds
14-day full refund, no questions asked. Email support@stacklis.com with your Stripe receipt.
5. Saved scenes & exports
Scenes you save are written as JSON files to your own device. We do not host, mirror, or back them up. The scene file format is versioned; future versions of the app will load older files but we cannot guarantee the reverse.
6. Acceptable use
Don't try to break the site for other users (DDoS, scraping, etc.) and don't use the brand or assets to misrepresent the product. Beyond that, the simulator runs locally — there's not much you can do that would harm anyone but yourself.
7. No warranty
The app is provided "as is" without warranty of any kind. We do not guarantee that the simulator is bug-free, accurate to any specific level of physical realism, or suitable for any particular purpose. Don't use it as the basis for engineering, safety, or scientific decisions.
8. Limitation of liability
To the maximum extent permitted by law, Stacklis is not liable for any indirect, consequential, or incidental damages arising from your use of the app. Total liability for any direct claim is capped at what you paid for Pro (or zero if you only used the free edition).
9. Privacy
See the Privacy Policy. Short version: we collect nothing personal and run no analytics.
10. Changes
We may update these terms. Material changes will be announced in-app and the "Effective" date at the top of this page will move. Continued use after changes means you accept them.
11. Contact
Questions: support@stacklis.com.