EventHandlerUI.cs

using UnityEngine;
using System.Collections;
using Image = UnityEngine.UI.Image;

public class EventHandlerUI : MonoBehaviour {

    public GameObject bulletPrefab;
    public Color pausedColor;

	// Use this for initialization
	void Start () {
	
	}
	
	// Update is called once per frame
	void Update () {
	
	}

    public void GunButtonClick()
    {
        // Grab our player plane and create a copy of the bullet from the prefab
        var plane = GameObject.FindWithTag("Player");
        var bullet = Instantiate(bulletPrefab, plane.transform.position, plane.transform.rotation) as GameObject;
        // Tell the physics engine to ignore collision between the bullet and our plane
        Physics2D.IgnoreCollision(bullet.GetComponent<Collider2D>(), plane.GetComponent<Collider2D>());
        // Destroy the bullet after 1 second (basically once it leaves the scene)
        Destroy(bullet, 1f);
    }

    public void MissileButtonClick()
    {
        Debug.Log("Pew pew pew");
    }

    public void NukeButtonClick()
    {
        GameObject.Find("Score").GetComponent<ScoreManager>().AddScore(1000);
        Debug.Log("Pew pew pew");
    }

    public void GearButtonClick()
    {
        // If time scale is greater then 0, that means its running so we need to pause 
        if (Time.timeScale > 0)
        {
            // Set timescale to 0 to prevent the game from running and set the image that is part of the canvas to semi opaque
            Time.timeScale = 0;
            gameObject.GetComponent<Image>().color = pausedColor;
            Debug.Log("Game paused");
        }
        else
        {
            // Set timescale to 1 to allow the game to run at normal speed and set the image that is part of the canvas to transparent
            Time.timeScale = 1;
            gameObject.GetComponent<Image>().color = Color.clear;
            Debug.Log("Game Resumed");
        }
    }
}