Flame — rising, shrinking, fading, adding

Fire = particles that rise, shrink, fade from yellow to orange to nothing, wobble sideways, and use additive blending (overlaps get brighter, because fire is made of light). Each of those five words is one line below.

const parts = [];
const baseX = W / 2, baseY = H * 0.8;

onFrame((dt, t) => {
  // spawn ~4 particles per frame at the base
  for (let i = 0; i < 4; i++) {
    parts.push({
      x: baseX + rand(-10, 10), y: baseY,
      vx: rand(-8, 8),
      vy: rand(-90, -50),               // rise
      life: rand(0.4, 0.9), maxLife: 0.9,
      size: rand(6, 12)
    });
  }

ctx.clearRect(0, 0, W, H);
  ctx.globalCompositeOperation = "lighter";   // ADDITIVE: light adds up

for (let i = parts.length - 1; i >= 0; i--) {
    const p = parts[i];
    p.life -= dt;
    if (p.life <= 0) { parts.splice(i, 1); continue; }
    const u = p.life / p.maxLife;       // 1 = newborn, 0 = dying
    p.x += (p.vx + Math.sin(t * 6 + p.y * 0.05) * 18) * dt;  // wobble
    p.y += p.vy * dt;
    // colour ramp: newborn = pale yellow, dying = deep orange
    const r = 255, g = Math.floor(120 + 135 * u), b = Math.floor(40 * u);
    ctx.fillStyle = "rgba(" + r + "," + g + "," + b + "," + (0.16 * u) + ")";
    ctx.beginPath();
    ctx.arc(p.x, p.y, p.size * u, 0, 7);      // shrink as it dies
    ctx.fill();
  }
  ctx.globalCompositeOperation = "source-over"; // back to normal
});

Soft, warm, and endlessly hypnotic — from ~35 lines with no images. Change the numbers and the fire changes species.

Try tweaking: rise speed rand(-90,-50) → rand(-30,-15) for lazy smoke-fire · the colour line: swap red/green for a blue-green ghost flame (r = 40*u, g = 180, b = 255) · wobble strength 18 → 60 for wind · spawn count 4 → 1 for a candle. Delete the "lighter" line and see how much additive blending was doing.

In Godot: GPUParticles2D configured with these same choices, commented — download flame.gd from the Godot project. In Unity: Particle System — Start Speed up, Lifetime 0.7, Color-over-Lifetime yellow→orange→transparent, Size-over-Lifetime shrinking, additive material. Retune each and you've made fire, not copied it. In Unreal: Niagara's Fountain template already contains every module named here — same retune. Chapter 06.