Simple Way Of Using Line of Sight?

I'm just curious whether you could make something that relies on a line of sight, without using a huge complicated script that makes many small invisible parts to fit into corners and etc.

I know I can use Invisible blocks, but I was thinking more towards "Zobmie won't come towards you unless it sees you through a window without a part blocking it.

Maybe I can use rays or whatever they're called.

I'm kind of a noob at some of these things.

This isn't a request or anything, I was just wondering if anyone knew of a simple way of doing it.