Noniv/snowflow_demo ? reverse-engineered prompt

Build me a browser based snowy mountain demo that feels like a playable tech showcase, not a normal game.

I want to be able to walk around with WASD, look with the mouse, zoom with the wheel, sprint with Shift, and click to capture the pointer. Right mouse should let me carve through the snow and leave a wake, and the number keys 1 to 5 should trigger different snow and ice spells. Add an F1 or backtick overlay with live sliders for the main visual settings, plus a simple performance panel and a few debug views.

Everything should be generated in real time on the GPU, so no textures, meshes, HDRIs, or animation files. The scene should include procedural terrain, snow deformation that persists, a procedural character, cloth, water effects, atmosphere, shadows, and post processing. Make it look dramatic and polished, and if the browser does not support WebGPU, show a clear message and stop. If needed, look up the current docs online.