Sparks — the four-line physics

A particle system is "spawn lots of small things and let simple rules move them." The rules here are four lines: move by velocity, add gravity, lose life, draw at alpha = life/maxLife. Press Run, then click the canvas to burst.

const GRAVITY = 340;
const parts = [];

canvas.onclick = (e) => {
  const r = canvas.getBoundingClientRect();
  burst(e.clientX - r.left, e.clientY - r.top);
};

burst(W / 2, H * 0.6);                     // one free burst to start

onFrame((dt) => {
  ctx.clearRect(0, 0, W, H);
  for (const p of parts) {
    if (p.life <= 0) continue;
    // ---- the entire physics of a spark ----
    p.x += p.vx * dt;
    p.y += p.vy * dt;
    p.vy += GRAVITY * dt;
    p.life -= dt;
    // ---------------------------------------
    ctx.globalAlpha = Math.max(0, p.life / p.maxLife);
    ctx.fillStyle = Math.random() < 0.6 ? "#5A63C8" : "#D6A878";
    ctx.beginPath();
    ctx.arc(p.x, p.y, 2.2, 0, 7);
    ctx.fill();
  }
  ctx.globalAlpha = 1;
  // the dead leave the array — otherwise every click grows it forever
  for (let i = parts.length - 1; i >= 0; i--) if (parts[i].life <= 0) parts.splice(i, 1);
});

Click anywhere on the canvas for more bursts. Every game engine's particle panel is a form that fills in these same numbers.

Try tweaking: GRAVITY to −340 (sparks fall up) · particle count 48 → 200 · speed range to rand(10, 60) for a soft puff · lifetime to 4 seconds for slow embers. One number each — and each one is a different effect with a different name in someone's tutorial.

In Godot: the same values set on CPUParticles2D, entirely in code — download sparks.gd from the Godot project. In Unity: a Particle System with Burst emission + gravity modifier — the inspector fields map one-to-one to these constants. In Unreal: Niagara burst emitter, same story. Chapter 06 names the mapping.