Help to create a "target"

Unity Engine
1

Hi guys!
I’m a totally noob with unity and JavaScript so I need your help.
I try to create a target at the center of the screen which can activate an effect when it touches a game object in the scene.
How can do that?
Thanks you.

2

If the target is on the center of your camera, you can maybe record it position and use it to lauch the effect.

It must exist an easier solution but mine can works :roll:

Faithfully