Trigger Pause Screen when escape key is pressed?

I want a pause menu to show up when I press the escape key. Here is my script.

using UnityEngine; using System.Collections;

public class PauseMenu : MonoBehaviour {

 private int buttonWidth = 200;
 private int buttonHeight = 50;
 private int groupWidth = 200;
 private int groupHeight = 170;
 bool paused = false;

 void Start ()
 {
     GameObject.Find ("Player").GetComponent<MouseLook>().enabled = true;
     Screen.lockCursor = true;
     Time.timeScale = 1;
 }

 void OnGUI()
 {
     if(paused)
     {
         GUI.BeginGroup(new Rect(((Screen.width/2) - (groupWidth/2)),((Screen.height/2) - (groupHeight/2)), groupWidth, groupHeight));
         if(GUI.Button (new Rect(0,0,buttonWidth, buttonHeight),"Main Menu"))
         {
             Application.LoadLevel("MainMenu");
         }
         if(GUI.Button (new Rect(0,60,buttonWidth,buttonHeight),"Resume Game"))
         {
             Application.LoadLevel(Application.loadedLevel);
         }
         if(GUI.Button (new Rect(0,120,buttonWidth,buttonHeight),"Quit Game"))
         {
             Application.Quit();
         }
         GUI.EndGroup();
     }
 }

 void Update ()
 {
     if(Input.GetKeyUp (KeyCode.Escape))
         paused = togglePause();
 }

 bool togglePause()
 {
     if(Time.timeScale == 0)
     {
         GameObject.Find ("Player").GetComponent<MouseLook>().enabled = true;
         Screen.lockCursor = true;
         Time.timeScale = 1;
         return(false);
     }
     else
     {
         GameObject.Find ("Player").GetComponent<MouseLook>().enabled = false;
         Screen.lockCursor = false;
         Time.timeScale = 0;
         return(true);
     }
 }

}