Method update

packages/melonjs/src/particles/particle.ts:150–235

* Update the Particle * This is automatically called by the game manager game * @ignore * @param dt - time since the last update in milliseconds

(dt: number)

	 * @param dt - time since the last update in milliseconds
	 */
	override update(dt: number) {
		// move things forward independent of the current frame rate
		const skew = dt * this._deltaInv;

		// Decrease particle life
		this.life = this.life > dt ? this.life - dt : 0;

		if (this.alive && this.life <= 0) {
			const parent = this.ancestor as Container;
			// use true for keepalive since we recycle the instance directly here after
			parent.removeChild(this, true);
			particlePool.release(this);
			this.alive = false;
			return false;
		}

		// Calculate the particle Age Ratio
		const ageRatio = this.life / this.startLife;

		// Resize the particle as particle Age Ratio
		let scale = this.startScale;
		if (this.startScale > this.endScale) {
			scale *= ageRatio;
			scale = scale < this.endScale ? this.endScale : scale;
		} else if (this.startScale < this.endScale) {
			scale /= ageRatio;
			scale = scale > this.endScale ? this.endScale : scale;
		}

		// Set the particle opacity as Age Ratio
		this.alpha = ageRatio;

		// Adjust the particle velocity
		this.vel.x += this.wind * skew;
		this.vel.y += this.gravity * skew;

		// If necessary update the rotation of particle in accordance the particle trajectory
		const angle = this.followTrajectory
			? Math.atan2(this.vel.y, this.vel.x)
			: this._angle;

		this.pos.x += this.vel.x * skew;
		this.pos.y += this.vel.y * skew;

		// Update particle transform — closed-form of the 4-step builder
		//   ScaleAndTranslate · T(half) · R(θ) · T(−half)
		// folded into a single setTransform() to skip 3 matrix multiplies per
		// particle per frame. See `closed-form equivalence` tests in
		// tests/emitter.spec.js for derivation + regression coverage.
		const halfW = this._halfW;
		const halfH = this._halfH;
		const cos = Math.cos(angle);
		const sin = Math.sin(angle);
		const sCos = scale * cos;
		const sSin = scale * sin;
		this.currentTransform.setTransform(
			sCos,
			sSin,