Suspense In Stranger Things

In “Stranger Things“, the DUFFER Brothers attempt to create to maximum amount of suspense by keeping evil as unknown as the victims state and even why were they chosen specifically which is very important for letting the audience imagination work a little bit to guess what actually happens .. But we are often surprised by the scenario.
Duffer brothers begin the film by a confusing scene in which a scientist is running away from an unknown danger but we don’t know what did actually happen. Then the story leads to the disappearance of a little kid. At that point, we can see that the lightning helped hiding the chaser because we couldn’t see anything despites of a shadow. It was certainly intended so we cannot recognize what the bad guy or thing