Add fullscreen firework emoji confetti and fix Linux URL paste.

Sparkle 🎆/🎇 from the jumbo emoji with a lightweight particle fountain that piles on the floor. Prefer text/plain over sticky clipboard images on Linux so address-bar URLs do not also attach a leftover bitmap.

src/app/features/room/emoji-confetti/fireworkParticleEngine.ts

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+/**
+ * Old-school fullscreen firework fountain — no physics engine.
+ * Position/velocity arrays, gravity, floor bounce, settle into a pile.
+ * Same vibe as late-90s/MSN page effects, just with emoji.
+ */
+import { BurstPoint } from './burstOrigin';
+import { pickParticleEmoji, type EmojiBurstProfile } from './emojiParticleProfiles';
+
+const EMOJI_CACHE_PX = 40;
+const EMOJI_CACHE_SCALE = 2;
+
+const SPAWN_WINDOW_MS = 2200;
+const SETTLE_HOLD_MS = 7800;
+const FADE_MS = 800;
+export const FIREWORK_TOTAL_MS = SETTLE_HOLD_MS + FADE_MS;
+
+const SPARKLE_IN_MS = 120;
+const MAX_SPAWNS_PER_FRAME = 6;
+const FLOOR_PAD = 8;
+const BOUNCE = 0.38;
+const DRAG = 0.992;
+const SETTLE_SPEED = 55;
+const PILE_CELL = 22;
+
+type SpawnItem = {
+  atMs: number;
+  emoji: string;
+  fontSize: number;
+};
+
+export type FireworkParticle = {
+  x: number;
+  y: number;
+  vx: number;
+  vy: number;
+  spin: number;
+  angle: number;
+  emoji: string;
+  emojiCanvas: HTMLCanvasElement;
+  drawSize: number;
+  halfSize: number;
+  bornAt: number;
+  settled: boolean;
+};
+
+export type FireworkSim = {
+  particles: FireworkParticle[];
+  profile: EmojiBurstProfile;
+  width: number;
+  height: number;
+  origin: BurstPoint;
+  startMs: number;
+  spawnPlan: SpawnItem[];
+  spawnCursor: number;
+  floorY: number;
+  /** Column stack heights for the settled pile (in cells). */
+  pileCols: Uint16Array;
+  pileCanvas: HTMLCanvasElement | null;
+  pileCtx: CanvasRenderingContext2D | null;
+  flyingCount: number;
+};
+
+const emojiCanvasCache = new Map<string, HTMLCanvasElement>();
+
+function lerp(min: number, max: number): number {
+  return min + Math.random() * (max - min);
+}
+
+function getEmojiCanvas(emoji: string): HTMLCanvasElement {
+  const cached = emojiCanvasCache.get(emoji);
+  if (cached) return cached;
+
+  const size = EMOJI_CACHE_PX * EMOJI_CACHE_SCALE;
+  const canvas = document.createElement('canvas');
+  canvas.width = size;
+  canvas.height = size;
+  const ctx = canvas.getContext('2d');
+  if (ctx) {
+    ctx.textAlign = 'center';
+    ctx.textBaseline = 'middle';
+    ctx.imageSmoothingEnabled = false;
+    ctx.font = `${EMOJI_CACHE_PX}px "Apple Color Emoji", "Segoe UI Emoji", "Noto Color Emoji", sans-serif`;
+    ctx.fillText(emoji, size / 2, size / 2);
+  }
+  emojiCanvasCache.set(emoji, canvas);
+  return canvas;
+}
+
+function buildSpawnPlan(
+  profile: EmojiBurstProfile,
+  primaryEmoji: string,
+  startMs: number
+): SpawnItem[] {
+  const plan: SpawnItem[] = [
+    {
+      atMs: startMs,
+      emoji: primaryEmoji,
+      fontSize: lerp(profile.heroFontSizeMin, profile.heroFontSizeMax),
+    },
+  ];
+
+  const count = profile.particleCount;
+  for (let i = 0; i < count; i += 1) {
+    const slot = (i + 0.5) / count;
+    const eased = slot * slot;
+    plan.push({
+      atMs:
+        startMs +
+        80 +
+        eased * SPAWN_WINDOW_MS +
+        (Math.random() - 0.5) * 70,
+      emoji: pickParticleEmoji(profile, primaryEmoji),
+      fontSize: lerp(profile.fontSizeMin, profile.fontSizeMax),
+    });
+  }
+
+  plan.sort((a, b) => a.atMs - b.atMs);
+  return plan;
+}
+
+function ensurePile(sim: FireworkSim): CanvasRenderingContext2D {
+  if (sim.pileCanvas && sim.pileCtx) return sim.pileCtx;
+  const canvas = document.createElement('canvas');
+  canvas.width = sim.width;
+  canvas.height = sim.height;
+  const ctx = canvas.getContext('2d');
+  if (!ctx) throw new Error('firework pile unsupported');
+  ctx.imageSmoothingEnabled = false;
+  sim.pileCanvas = canvas;
+  sim.pileCtx = ctx;
+  return ctx;
+}
+
+function stampSettled(sim: FireworkSim, p: FireworkParticle) {
+  const ctx = ensurePile(sim);
+  const rad = (p.angle * Math.PI) / 180;
+  const cos = Math.cos(rad);
+  const sin = Math.sin(rad);
+  ctx.setTransform(cos, sin, -sin, cos, p.x, p.y);
+  ctx.globalAlpha = 1;
+  ctx.drawImage(p.emojiCanvas, -p.halfSize, -p.halfSize, p.drawSize, p.drawSize);
+  ctx.setTransform(1, 0, 0, 1, 0, 0);
+}
+
+function spawnOne(sim: FireworkSim, item: SpawnItem, now: number) {
+  const { profile, origin } = sim;
+  const jitter = Math.max(4, (origin.maskRadius ?? 28) * 0.25);
+  const angle = Math.random() * Math.PI * 2;
+  const speed = lerp(profile.speedMin, profile.speedMax);
+  const launchUp = lerp(profile.launchUpMin, profile.launchUpMax);
+  const drawSize = item.fontSize * EMOJI_CACHE_SCALE * 0.85;
+
+  sim.particles.push({
+    x: origin.x + (Math.random() - 0.5) * jitter,
+    y: origin.y + (Math.random() - 0.5) * jitter,
+    vx: Math.cos(angle) * speed + (Math.random() - 0.5) * 40,
+    vy: Math.sin(angle) * speed - launchUp,
+    spin: lerp(profile.spinMin, profile.spinMax) * 0.35,
+    angle: (Math.random() - 0.5) * 40,
+    emoji: item.emoji,
+    emojiCanvas: getEmojiCanvas(item.emoji),
+    drawSize,
+    halfSize: drawSize / 2,
+    bornAt: now,
+    settled: false,
+  });
+  sim.flyingCount += 1;
+}
+
+function settleParticle(sim: FireworkSim, p: FireworkParticle) {
+  const cols = sim.pileCols.length;
+  let col = Math.floor(p.x / PILE_CELL);
+  if (col < 0) col = 0;
+  if (col >= cols) col = cols - 1;
+
+  // Prefer the intended column; spill to neighbors if that stack is already tall.
+  let bestCol = col;
+  let bestH = sim.pileCols[col];
+  for (const delta of [0, -1, 1, -2, 2]) {
+    const c = col + delta;
+    if (c < 0 || c >= cols) continue;
+    if (sim.pileCols[c] < bestH) {
+      bestH = sim.pileCols[c];
+      bestCol = c;
+    }
+  }
+
+  const stack = sim.pileCols[bestCol];
+  sim.pileCols[bestCol] = stack + 1;
+  p.x = bestCol * PILE_CELL + PILE_CELL * 0.5 + (Math.random() - 0.5) * 6;
+  p.y = sim.floorY - stack * (PILE_CELL * 0.72) - p.halfSize;
+  p.vx = 0;
+  p.vy = 0;
+  p.spin = 0;
+  p.settled = true;
+  sim.flyingCount = Math.max(0, sim.flyingCount - 1);
+  stampSettled(sim, p);
+}
+
+export function createFireworkSim(
+  widthPx: number,
+  heightPx: number,
+  originPx: BurstPoint,
+  primaryEmoji: string,
+  profile: EmojiBurstProfile,
+  startMs = performance.now()
+): FireworkSim {
+  const colCount = Math.max(8, Math.ceil(widthPx / PILE_CELL));
+  return {
+    particles: [],
+    profile,
+    width: widthPx,
+    height: heightPx,
+    origin: originPx,
+    startMs,
+    spawnPlan: buildSpawnPlan(profile, primaryEmoji, startMs),
+    spawnCursor: 0,
+    floorY: heightPx - FLOOR_PAD,
+    pileCols: new Uint16Array(colCount),
+    pileCanvas: null,
+    pileCtx: null,
+    flyingCount: 0,
+  };
+}
+
+/** @returns false when the burst should be removed. */
+export function stepFireworkSim(sim: FireworkSim, now: number, dtSeconds: number): boolean {
+  if (now - sim.startMs > FIREWORK_TOTAL_MS) return false;
+
+  const dt = Math.min(dtSeconds, 0.05);
+  const g = sim.profile.gravity;
+
+  let spawned = 0;
+  while (
+    spawned < MAX_SPAWNS_PER_FRAME &&
+    sim.spawnCursor < sim.spawnPlan.length &&
+    sim.spawnPlan[sim.spawnCursor].atMs <= now
+  ) {
+    spawnOne(sim, sim.spawnPlan[sim.spawnCursor], now);
+    sim.spawnCursor += 1;
+    spawned += 1;
+  }
+
+  const floor = sim.floorY;
+  const left = 4;
+  const right = sim.width - 4;
+
+  for (let i = 0; i < sim.particles.length; i += 1) {
+    const p = sim.particles[i];
+    if (p.settled) continue;
+
+    p.vy += g * dt;
+    p.vx *= DRAG;
+    p.vy *= DRAG;
+    p.x += p.vx * dt;
+    p.y += p.vy * dt;
+    p.angle += p.spin * dt;
+
+    if (p.x < left) {
+      p.x = left;
+      p.vx = Math.abs(p.vx) * BOUNCE;
+    } else if (p.x > right) {
+      p.x = right;
+      p.vx = -Math.abs(p.vx) * BOUNCE;
+    }
+
+    if (p.y >= floor - p.halfSize) {
+      p.y = floor - p.halfSize;
+      const speed = Math.hypot(p.vx, p.vy);
+      if (speed < SETTLE_SPEED || Math.abs(p.vy) < SETTLE_SPEED * 0.55) {
+        settleParticle(sim, p);
+      } else {
+        p.vy = -Math.abs(p.vy) * BOUNCE;
+        p.vx *= 0.85;
+        p.spin *= 0.7;
+      }
+    }
+  }
+
+  return true;
+}
+
+export function drawFireworkSim(
+  context: CanvasRenderingContext2D,
+  sim: FireworkSim,
+  now: number
+) {
+  const elapsed = now - sim.startMs;
+  let fade = 1;
+  if (elapsed >= SETTLE_HOLD_MS) {
+    fade = 1 - Math.min(1, (elapsed - SETTLE_HOLD_MS) / FADE_MS);
+  }
+
+  context.setTransform(1, 0, 0, 1, 0, 0);
+  context.imageSmoothingEnabled = false;
+
+  if (sim.pileCanvas) {
+    context.globalAlpha = fade;
+    context.drawImage(sim.pileCanvas, 0, 0);
+  }
+
+  for (let i = 0; i < sim.particles.length; i += 1) {
+    const p = sim.particles[i];
+    if (p.settled) continue;
+
+    const ageMs = now - p.bornAt;
+    if (ageMs < 0) continue;
+
+    let opacity = fade;
+    let scale = 1;
+    if (ageMs < SPARKLE_IN_MS) {
+      const t = ageMs / SPARKLE_IN_MS;
+      const appear = t * t * (3 - 2 * t);
+      scale = 0.5 + 0.65 * appear;
+      opacity *= appear;
+    }
+    if (opacity <= 0.02) continue;
+
+    const rad = (p.angle * Math.PI) / 180;
+    const size = p.drawSize * scale;
+    const half = size / 2;
+    const cos = Math.cos(rad);
+    const sin = Math.sin(rad);
+
+    context.globalAlpha = opacity;
+    context.setTransform(cos, sin, -sin, cos, p.x, p.y);
+    context.drawImage(p.emojiCanvas, -half, -half, size, size);
+  }
+
+  context.globalAlpha = 1;
+  context.setTransform(1, 0, 0, 1, 0, 0);
+}
+
+export function getFireworkDpr(): number {
+  return 1;
+}