immersive-garden/igpu — reverse-engineered prompt

Build me a minimal WebGPU starter repo that feels easy to read and easy to grow into my own little engine. I want it to stay very close to native WebGPU, with only a thin layer on top so I can still mix in raw GPU calls when needed.

It should cover the basics for rendering and compute, with a renderer, camera, transforms, meshes, geometry, textures, render targets, and simple math helpers. I want to write WGSL shaders directly, not use a visual shader system, and have simple wrappers that hook up render shaders and compute kernels without hiding too much. Shader hot reload would be great too.

Please add a few optional extras like orbit controls, raycasting, animation, glTF loading, cubemaps, video textures, and a small GUI. Include browser examples I can switch between, plus at least one nice physically based lighting demo using environment lighting.

Make this a starter project I can fork, not a published package. Keep the codebase agent friendly and well mapped for future edits. If you need details, check the project docs and current WebGPU guidance online.