SayantanXBTC/PhysVerse ? reverse-engineered prompt

Build me a modern 3D physics sandbox web app where people can create and play with physics simulations right in the browser. I want a dark, polished interface with real time 3D visuals, smooth controls, and a few built in simulation types like projectile motion, spring and mass, and orbit style gravity.

Users should be able to sign up and log in, save their simulations, edit or delete them later, and choose whether a simulation is private or public. There should also be a public gallery where people can browse shared simulations, open them, and clone them into their own account. Make it feel fun and easy to use, but still solid and production ready.

Please set it up with a clear frontend and backend, include validation and secure authentication, and use a database so saved simulations persist. If you need current docs for any libraries, look them up online and build it the best way.