on mouse unity code example

Example 1: unity left mouse button

//Key Code in the Input Project Settings is "mouse 0"
Input.GetKey(KeyCode.Mouse0))

Example 2: unity on mousewheel down

if (Input.GetAxis("Mouse ScrollWheel") > 0f) // forward
 {

 }
if (Input.GetAxis("Mouse ScrollWheel") < 0f) // backwards
{
               
}