(function () {
  if (window.matchMedia('(prefers-reduced-motion: reduce)').matches) return;
  if (!window.WebGLRenderingContext || !window.THREE) return;

  const canvas = document.getElementById('scene');
  if (!canvas) return;

  const root = document.documentElement;
  const readVar = (name) => getComputedStyle(root).getPropertyValue(name).trim();
  const readOpacity = () => parseFloat(readVar('--scene-opacity')) || 0.18;

  const scene = new THREE.Scene();
  const camera = new THREE.PerspectiveCamera(
    60, window.innerWidth / window.innerHeight, 0.1, 100
  );
  const renderer = new THREE.WebGLRenderer({ canvas, antialias: true, alpha: true });
  renderer.setSize(window.innerWidth, window.innerHeight, false);
  renderer.setPixelRatio(Math.min(window.devicePixelRatio || 1, 2));

  const geometry = new THREE.TorusKnotGeometry(2.5, 0.4, 130, 20);
  const material = new THREE.MeshPhongMaterial({
    color: readVar('--accent') || '#c03a28',
    wireframe: true,
    transparent: true,
    opacity: readOpacity()
  });
  const core = new THREE.Mesh(geometry, material);
  scene.add(core);

  scene.add(new THREE.AmbientLight(0xffffff, 0.6));
  const dir = new THREE.DirectionalLight(0xffffff, 0.8);
  dir.position.set(5, 5, 5);
  scene.add(dir);

  const BASE_Z = 9;
  camera.position.z = BASE_Z;

  let scrollY = window.scrollY || 0;
  window.addEventListener('scroll', () => {
    scrollY = window.scrollY || 0;
  }, { passive: true });

  let baseOpacity = readOpacity();

  let running = true;
  function tick() {
    if (!running) return;
    requestAnimationFrame(tick);

    // Continuous slow drift.
    core.rotation.y += 0.0015;
    core.rotation.z += 0.0006;

    // Scroll-driven motion: zoom in, scale up, tilt.
    const s = Math.min(scrollY, 2000);
    camera.position.z = BASE_Z - s * 0.0022;
    const scale = 1 + s * 0.00035;
    core.scale.set(scale, scale, scale);
    core.rotation.x = s * 0.0008;

    // Fade past hero so feature cards stay readable.
    const vh = window.innerHeight;
    const fadeStart = vh * 0.5;
    const fadeEnd = vh * 1.4;
    const t = Math.max(0, Math.min(1, (scrollY - fadeStart) / (fadeEnd - fadeStart)));
    material.opacity = baseOpacity * (1 - t * 0.92);

    renderer.render(scene, camera);
  }
  tick();

  window.addEventListener('resize', () => {
    camera.aspect = window.innerWidth / window.innerHeight;
    camera.updateProjectionMatrix();
    renderer.setSize(window.innerWidth, window.innerHeight, false);
  });

  document.addEventListener('visibilitychange', () => {
    if (document.hidden) {
      running = false;
    } else if (!running) {
      running = true;
      tick();
    }
  });

  const mql = window.matchMedia('(prefers-color-scheme: dark)');
  const updateTheme = () => {
    const accent = readVar('--accent');
    if (accent) material.color.set(accent);
    baseOpacity = readOpacity();
  };
  if (mql.addEventListener) {
    mql.addEventListener('change', updateTheme);
  } else if (mql.addListener) {
    mql.addListener(updateTheme);
  }
})();