feat: add constellation system connecting nearby stars with faint lines

- Create 800-star field using Three.js Points with randomized sizes
- Build constellation lines connecting stars within distance threshold
- Limit connections per star (max 3) to avoid visual clutter
- Animate star field and lines with slow rotation + mouse parallax
- Pulse constellation line opacity for a living, breathing effect
- Wire Three.js import map in index.html for zero-bundler setup
- Add base CSS design system (dark space theme, --color-* vars)

Fixes #114

app.js

@@ -1,12 +1,161 @@
-// ... existing code ...
+import * as THREE from 'three';
+
+// === COLOR PALETTE ===
+const NEXUS = {
+  colors: {
+    bg: 0x000008,
+    starCore: 0xffffff,
+    starDim: 0x8899cc,
+    constellationLine: 0x334488,
+    constellationFade: 0x112244,
+    accent: 0x4488ff,
+  }
+};
+
+// === SCENE SETUP ===
+const scene = new THREE.Scene();
+scene.background = new THREE.Color(NEXUS.colors.bg);
+
+const camera = new THREE.PerspectiveCamera(75, window.innerWidth / window.innerHeight, 0.1, 2000);
+camera.position.set(0, 0, 5);
+
+const renderer = new THREE.WebGLRenderer({ antialias: true });
+renderer.setPixelRatio(window.devicePixelRatio);
+renderer.setSize(window.innerWidth, window.innerHeight);
+document.body.appendChild(renderer.domElement);
+
+// === STAR FIELD ===
+const STAR_COUNT = 800;
+const STAR_SPREAD = 400;
+const CONSTELLATION_DISTANCE = 30; // max distance to draw a line between stars
+
+const starPositions = [];
+const starGeo = new THREE.BufferGeometry();
+const posArray = new Float32Array(STAR_COUNT * 3);
+const sizeArray = new Float32Array(STAR_COUNT);
+
+for (let i = 0; i < STAR_COUNT; i++) {
+  const x = (Math.random() - 0.5) * STAR_SPREAD;
+  const y = (Math.random() - 0.5) * STAR_SPREAD;
+  const z = (Math.random() - 0.5) * STAR_SPREAD;
+  posArray[i * 3] = x;
+  posArray[i * 3 + 1] = y;
+  posArray[i * 3 + 2] = z;
+  sizeArray[i] = Math.random() * 2.5 + 0.5;
+  starPositions.push(new THREE.Vector3(x, y, z));
+}
+
+starGeo.setAttribute('position', new THREE.BufferAttribute(posArray, 3));
+starGeo.setAttribute('size', new THREE.BufferAttribute(sizeArray, 1));
+
+const starMaterial = new THREE.PointsMaterial({
+  color: NEXUS.colors.starCore,
+  size: 0.6,
+  sizeAttenuation: true,
+  transparent: true,
+  opacity: 0.9,
+});
+
+const stars = new THREE.Points(starGeo, starMaterial);
+scene.add(stars);
+
+// === CONSTELLATION LINES ===
+// Connect nearby stars with faint lines, limited to avoid clutter
+function buildConstellationLines() {
+  const linePositions = [];
+  const MAX_CONNECTIONS_PER_STAR = 3;
+  const connectionCount = new Array(STAR_COUNT).fill(0);
+
+  for (let i = 0; i < STAR_COUNT; i++) {
+    if (connectionCount[i] >= MAX_CONNECTIONS_PER_STAR) continue;
+
+    // Find nearest neighbors
+    const neighbors = [];
+    for (let j = i + 1; j < STAR_COUNT; j++) {
+      if (connectionCount[j] >= MAX_CONNECTIONS_PER_STAR) continue;
+      const dist = starPositions[i].distanceTo(starPositions[j]);
+      if (dist < CONSTELLATION_DISTANCE) {
+        neighbors.push({ j, dist });
+      }
+    }
+
+    // Sort by distance and connect closest ones
+    neighbors.sort((a, b) => a.dist - b.dist);
+    const toConnect = neighbors.slice(0, MAX_CONNECTIONS_PER_STAR - connectionCount[i]);
+
+    for (const { j } of toConnect) {
+      linePositions.push(
+        starPositions[i].x, starPositions[i].y, starPositions[i].z,
+        starPositions[j].x, starPositions[j].y, starPositions[j].z
+      );
+      connectionCount[i]++;
+      connectionCount[j]++;
+    }
+  }
+
+  const lineGeo = new THREE.BufferGeometry();
+  lineGeo.setAttribute('position', new THREE.BufferAttribute(new Float32Array(linePositions), 3));
+
+  const lineMat = new THREE.LineBasicMaterial({
+    color: NEXUS.colors.constellationLine,
+    transparent: true,
+    opacity: 0.18,
+  });
+
+  return new THREE.LineSegments(lineGeo, lineMat);
+}
+
+const constellationLines = buildConstellationLines();
+scene.add(constellationLines);
+
+// === MOUSE-DRIVEN ROTATION ===
+let mouseX = 0;
+let mouseY = 0;
+let targetRotX = 0;
+let targetRotY = 0;
+
+document.addEventListener('mousemove', (e) => {
+  mouseX = (e.clientX / window.innerWidth - 0.5) * 2;
+  mouseY = (e.clientY / window.innerHeight - 0.5) * 2;
+});
+
+// === RESIZE HANDLER ===
+window.addEventListener('resize', () => {
+  camera.aspect = window.innerWidth / window.innerHeight;
+  camera.updateProjectionMatrix();
+  renderer.setSize(window.innerWidth, window.innerHeight);
+});
+
+// === ANIMATION LOOP ===
+const clock = new THREE.Clock();
+
+function animate() {
+  requestAnimationFrame(animate);
+  const elapsed = clock.getElapsedTime();
+
+  // Slow auto-rotation
+  targetRotX += (mouseY * 0.3 - targetRotX) * 0.02;
+  targetRotY += (mouseX * 0.3 - targetRotY) * 0.02;
+
+  stars.rotation.x = targetRotX + elapsed * 0.01;
+  stars.rotation.y = targetRotY + elapsed * 0.015;
+
+  constellationLines.rotation.x = stars.rotation.x;
+  constellationLines.rotation.y = stars.rotation.y;
+
+  // Subtle pulse on constellation opacity
+  constellationLines.material.opacity = 0.12 + Math.sin(elapsed * 0.5) * 0.06;
+
+  renderer.render(scene, camera);
+}
+
+animate();
 
 // === WEBSOCKET CLIENT ===
 import { wsClient } from './ws-client.js';
 
-// Initialize WebSocket client
 wsClient.connect();
 
-// Handle WebSocket events
 window.addEventListener('player-joined', (event) => {
   console.log('Player joined:', event.detail);
 });
@@ -19,9 +168,6 @@ window.addEventListener('chat-message', (event) => {
   console.log('Chat message:', event.detail);
 });
 
-// Clean up on page unload
 window.addEventListener('beforeunload', () => {
   wsClient.disconnect();
 });
-
-// ... existing code ...

index.html

@@ -14,10 +14,17 @@
   <meta name="twitter:description" content="A sovereign 3D world">
   <meta name="twitter:image" content="https://example.com/og-image.png">
   <link rel="manifest" href="/manifest.json">
+  <link rel="stylesheet" href="style.css">
+  <script type="importmap">
+    {
+      "imports": {
+        "three": "https://unpkg.com/three@0.183.0/build/three.module.js",
+        "three/addons/": "https://unpkg.com/three@0.183.0/examples/jsm/"
+      }
+    }
+  </script>
 </head>
 <body>
-  <!-- ... existing content ... -->
-
   <!-- Top Right: Audio Toggle -->
   <div id="audio-control" class="hud-controls" style="position: absolute; top: 8px; right: 8px;">
     <button id="audio-toggle" class="chat-toggle-btn" aria-label="Toggle ambient sound" style="background-color: var(--color-primary); color: var(--color-bg); padding: 4px 8px; border-radius: 4px; font-size: 12px; cursor: pointer;">
@@ -26,6 +33,6 @@
     <audio id="ambient-sound" src="ambient.mp3" loop></audio>
   </div>
 
-  <!-- ... existing content ... -->
+  <script type="module" src="app.js"></script>
 </body>
 </html>

style.css

@@ -1,12 +1,51 @@
+/* === DESIGN SYSTEM — NEXUS === */
+:root {
+  --color-bg: #000008;
+  --color-primary: #4488ff;
+  --color-secondary: #334488;
+  --color-text: #ccd6f6;
+  --color-text-muted: #4a5568;
+  --font-body: 'Courier New', monospace;
+}
+
+* {
+  margin: 0;
+  padding: 0;
+  box-sizing: border-box;
+}
+
+body {
+  background: var(--color-bg);
+  color: var(--color-text);
+  font-family: var(--font-body);
+  overflow: hidden;
+  width: 100vw;
+  height: 100vh;
+}
+
+canvas {
+  display: block;
+  position: fixed;
+  top: 0;
+  left: 0;
+}
+
+/* === HUD === */
+.hud-controls {
+  z-index: 10;
+}
+
 /* === AUDIO TOGGLE === */
 #audio-toggle {
   font-size: 14px;
-  background-color: var(--color-primary-primary);
+  background-color: var(--color-primary);
   color: var(--color-bg);
   padding: 4px 8px;
+  border: none;
   border-radius: 4px;
   font-family: var(--font-body);
   transition: background-color 0.3s ease;
+  cursor: pointer;
 }
 
 #audio-toggle:hover {