sctlcd/threejs-sci-fi-portal-effect — reverse-engineered prompt

Build me a desktop web page that shows an animated 3D science fiction portal effect, like a glowing wormhole or energy gateway, using Three.js.

I want it to feel like a visual demo rather than a full app. When someone opens the page, they should see a dramatic portal animation with particles, smoke or glow effects, and a dark sci fi mood. It should run locally in the browser with a simple dev server and be easy to deploy as a static site later.

Please include the basic page setup, the 3D scene, camera, animation loop, lighting, textures or image assets if needed, and make it responsive enough for normal desktop browser sizes. Keep the code clean and simple so I can tweak colors, speed, and portal shape later. Look up current Three.js or Vite docs online if you need to.