createParticle(initialize, behaviour) {
    const particle = this.parent.pool.get(Particle);
    this.setupParticle(particle, initialize, behaviour);
    this.dispatch("PARTICLE_CREATED", particle);

    return particle;
  }
Creates a single particle.

@param {Object|Array} [initialize] - Initialization parameters or array of initialization objects.
@param {Object|Array} [behaviour] - Behavior object or array of behavior objects.
@returns {Particle} The created particle.