Interactive 3D Mouse Scene

*,
*::before,
*::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  background: #030510;
  color: #f0f4fb;
  font-family: "Inter", "SF Pro Display", system-ui, sans-serif;
  overflow: hidden;
  height: 100vh;
}

#canvas-container {
  position: fixed;
  inset: 0;
  z-index: 0;
}
#canvas-container canvas {
  display: block;
  width: 100%;
  height: 100%;
}

.overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 2;
  text-align: center;
  padding: 3rem 2rem;
  pointer-events: none;
}

.eyebrow {
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.18em;
  color: #86e8ff;
  margin-bottom: 0.75rem;
  display: block;
}
h1 {
  font-size: clamp(2rem, 5vw, 3.5rem);
  font-weight: 700;
  letter-spacing: -0.03em;
  text-shadow: 0 0 40px rgba(134, 232, 255, 0.2);
}
.subtitle {
  font-size: clamp(0.85rem, 1.5vw, 1rem);
  color: rgba(255, 255, 255, 0.5);
  max-width: 420px;
  margin: 0.5rem auto 0;
  line-height: 1.5;
}

.btn-back {
  position: fixed;
  bottom: 2rem;
  left: 50%;
  transform: translateX(-50%);
  z-index: 10;
  padding: 0.6rem 1.5rem;
  border-radius: 999px;
  border: 1px solid rgba(134, 232, 255, 0.2);
  color: #86e8ff;
  text-decoration: none;
  font: 600 0.8rem / 1 "Inter", system-ui, sans-serif;
  background: rgba(3, 5, 16, 0.7);
  backdrop-filter: blur(8px);
  transition: all 0.25s;
}
.btn-back:hover {
  background: rgba(134, 232, 255, 0.08);
  border-color: #86e8ff;
}

if (!window.MotionPreference) {
  const __mql = window.matchMedia("(prefers-reduced-motion: reduce)");
  const __listeners = new Set();

  const MotionPreference = {
    prefersReducedMotion() {
      return __mql.matches;
    },
    setOverride(value) {
      const reduced = Boolean(value);
      document.documentElement.classList.toggle("reduced-motion", reduced);
      window.dispatchEvent(new CustomEvent("motion-preference", { detail: { reduced } }));
      for (const listener of __listeners) {
        try {
          listener({ reduced, override: reduced, systemReduced: __mql.matches });
        } catch {}
      }
    },
    onChange(listener) {
      __listeners.add(listener);
      try {
        listener({
          reduced: __mql.matches,
          override: null,
          systemReduced: __mql.matches,
        });
      } catch {}
      return () => __listeners.delete(listener);
    },
    getState() {
      return { reduced: __mql.matches, override: null, systemReduced: __mql.matches };
    },
  };

  window.MotionPreference = MotionPreference;
}

function prefersReducedMotion() {
  return window.MotionPreference.prefersReducedMotion();
}

function initDemoShell() {
  // No-op shim in imported standalone snippets.
}

import * as THREE from "three";

initDemoShell({
  title: "Interactive 3D Scene",
  category: "3d",
  tech: ["three.js", "instanced-mesh", "raycaster"],
});

let reduced = prefersReducedMotion();
if (reduced) document.documentElement.classList.add("reduced-motion");
window.addEventListener("motion-preference", (e) => {
  reduced = e.detail.reduced;
});

// Config
const GRID = 20; // 20x20 = 400 spheres
const SPACING = 0.6;
const REPULSION_RADIUS = 3;
const REPULSION_FORCE = 0.08;
const SPRING = 0.04;
const DAMPING = 0.88;

// Scene
const container = document.getElementById("canvas-container");
const scene = new THREE.Scene();
scene.background = new THREE.Color("#030510");

const camera = new THREE.PerspectiveCamera(55, window.innerWidth / window.innerHeight, 0.1, 100);
camera.position.set(0, 8, 10);
camera.lookAt(0, 0, 0);

const renderer = new THREE.WebGLRenderer({ antialias: true });
renderer.setSize(window.innerWidth, window.innerHeight);
renderer.setPixelRatio(Math.min(window.devicePixelRatio, 2));
container.appendChild(renderer.domElement);

// Lights
scene.add(new THREE.AmbientLight(0x222244, 0.8));
const dirLight = new THREE.DirectionalLight(0xffffff, 1.5);
dirLight.position.set(5, 8, 5);
scene.add(dirLight);
const pointLight = new THREE.PointLight(0x86e8ff, 2, 20);
pointLight.position.set(0, 3, 0);
scene.add(pointLight);

// Instanced mesh
const geo = new THREE.SphereGeometry(0.15, 16, 16);
const mat = new THREE.MeshStandardMaterial({ metalness: 0.6, roughness: 0.3 });
const count = GRID * GRID;
const mesh = new THREE.InstancedMesh(geo, mat, count);
scene.add(mesh);

// Particle state
const dummy = new THREE.Object3D();
const color = new THREE.Color();
const particles = [];
const halfGrid = ((GRID - 1) * SPACING) / 2;

for (let i = 0; i < GRID; i++) {
  for (let j = 0; j < GRID; j++) {
    const x = i * SPACING - halfGrid;
    const z = j * SPACING - halfGrid;
    particles.push({
      homeX: x,
      homeZ: z,
      x,
      y: 0,
      z,
      vx: 0,
      vy: 0,
      vz: 0,
    });
  }
}

// Mouse → 3D plane intersection
const mouse = new THREE.Vector2();
const raycaster = new THREE.Raycaster();
const intersectPlane = new THREE.Plane(new THREE.Vector3(0, 1, 0), 0);
const mouseWorld = new THREE.Vector3();

document.addEventListener("mousemove", (e) => {
  mouse.x = (e.clientX / window.innerWidth) * 2 - 1;
  mouse.y = -(e.clientY / window.innerHeight) * 2 + 1;
});

// Color palette
const coldColor = new THREE.Color("#86e8ff");
const warmColor = new THREE.Color("#ff40d6");

// Animate
const clock = new THREE.Clock();

function animate() {
  requestAnimationFrame(animate);
  const t = clock.getElapsedTime();

  // Raycast mouse to ground plane
  raycaster.setFromCamera(mouse, camera);
  raycaster.ray.intersectPlane(intersectPlane, mouseWorld);

  for (let i = 0; i < count; i++) {
    const p = particles[i];

    if (!reduced) {
      // Distance from mouse
      const dx = p.x - mouseWorld.x;
      const dz = p.z - mouseWorld.z;
      const dist = Math.sqrt(dx * dx + dz * dz);

      // Repulsion
      if (dist < REPULSION_RADIUS && dist > 0.01) {
        const force = (1 - dist / REPULSION_RADIUS) * REPULSION_FORCE;
        p.vx += (dx / dist) * force;
        p.vz += (dz / dist) * force;
        p.vy += force * 0.5; // push up too
      }

      // Spring back to home
      p.vx += (p.homeX - p.x) * SPRING;
      p.vz += (p.homeZ - p.z) * SPRING;
      p.vy += (0 - p.y) * SPRING;

      // Damping
      p.vx *= DAMPING;
      p.vy *= DAMPING;
      p.vz *= DAMPING;

      // Integrate
      p.x += p.vx;
      p.y += p.vy;
      p.z += p.vz;
    }

    // Update instance
    dummy.position.set(p.x, p.y, p.z);
    const scale = 1 + p.y * 0.8; // scale with height
    dummy.scale.setScalar(Math.max(scale, 0.3));
    dummy.updateMatrix();
    mesh.setMatrixAt(i, dummy.matrix);

    // Color by distance from mouse
    const dist = Math.sqrt((p.x - mouseWorld.x) ** 2 + (p.z - mouseWorld.z) ** 2);
    const t2 = Math.min(dist / REPULSION_RADIUS, 1);
    color.copy(warmColor).lerp(coldColor, t2);
    mesh.setColorAt(i, color);
  }

  mesh.instanceMatrix.needsUpdate = true;
  if (mesh.instanceColor) mesh.instanceColor.needsUpdate = true;

  // Subtle camera sway
  if (!reduced) {
    camera.position.x = Math.sin(t * 0.15) * 0.5;
    camera.lookAt(0, 0, 0);
  }

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

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

window.addEventListener("beforeunload", () => {
  geo.dispose();
  mat.dispose();
  renderer.dispose();
});

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Interactive 3D Scene — stealthisdesign</title>
  <link rel="stylesheet" href="style.css">
    <script type="importmap">{"imports":{"gsap":"https://esm.sh/gsap@3.13.0","gsap/ScrollTrigger":"https://esm.sh/gsap@3.13.0/ScrollTrigger","gsap/SplitText":"https://esm.sh/gsap@3.13.0/SplitText","gsap/Flip":"https://esm.sh/gsap@3.13.0/Flip","gsap/ScrambleTextPlugin":"https://esm.sh/gsap@3.13.0/ScrambleTextPlugin","gsap/TextPlugin":"https://esm.sh/gsap@3.13.0/TextPlugin","gsap/all":"https://esm.sh/gsap@3.13.0/all","gsap/":"https://esm.sh/gsap@3.13.0/","lenis":"https://esm.sh/lenis@1.1.13/dist/lenis.mjs","three":"https://esm.sh/three@0.171.0","three/addons/":"https://esm.sh/three@0.171.0/examples/jsm/"}}</script>
</head>
<body>
  <div id="canvas-container" aria-hidden="true"></div>

  <div class="overlay">
    <span class="eyebrow">Demo 10</span>
    <h1>Interactive 3D</h1>
    <p class="subtitle">A grid of 400 instanced spheres react to your mouse with repulsion physics and spring-based return. Colors shift by distance.</p>
  </div>

  <a href="/" class="btn-back">Back to Showcase</a>
  <script type="module" src="script.js"></script>
</body>
</html>