How to identify the shape of a line renderer.

Hello, i need help with a project i am doing, basically i have created a script that whenever you press the mouse button it create a new line renderer, and until you put your mouse up it will create a new points, so you can draw things with it. Anyway i would like after you press a key stop/start drawing that it identifys the shape of the thing that the line renderer built. Kinda like this game : http://www.nitrome.com/games/magictouch/

P.S: i am sorry for bad grammer, English isn't my first laungage