Making a 2D line?

Hey everyone,

I want to see if I can make a line when the user touches the screen on their phone and have two colliders that detect the start and end point.

Here is what I have in mind:

So I want the user to press on the semi-circle on the left and then pull the line down to the right semi-circle.

Can someone help? I really cant seem to t$$anonymous$$nk of a way to approach t$$anonymous$$s one?

Cheers,