The current mouse position in pixel coordinates. (Read Only)

The bottom-left of the screen or window is at (0, 0). The top-right of the screen or window is at (Screen.width, Screen.height).

	var particle : GameObject;
	function Update () {
		if (Input.GetButtonDown ("Fire1")) {
			// Construct a ray from the current mouse coordinates
			var ray : Ray = Camera.main.ScreenPointToRay (Input.mousePosition);
			if (Physics.Raycast (ray)) {
				// Create a particle if hit
				Instantiate (particle, transform.position, transform.rotation);
			}
		}
	}

using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    public GameObject particle;
    void Update() {
        if (Input.GetButtonDown("Fire1")) {
            Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
            if (Physics.Raycast(ray))
                Instantiate(particle, transform.position, transform.rotation) as GameObject;
            
        }
    }
}

import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	public particle as GameObject

	def Update() as void:
		if Input.GetButtonDown('Fire1'):
			ray as Ray = Camera.main.ScreenPointToRay(Input.mousePosition)
			if Physics.Raycast(ray):
				(Instantiate(particle, transform.position, transform.rotation) as GameObject)