Unity3d Popup Message

/// <summary>
/// Popup Note Script
///
/// Attach to a trigger object in the game.
/// You can use the graphic provided, please give credit to the author:
/// Shadows of Elear - Deviantart.com
///
/// You may use this script for commercial purposes
///
/// http://lostmystic.com
/// Written in Unity 4.3.1
/// </summary>
using UnityEngine;
using System.Collections;

public class TrigPopupMsg : MonoBehaviour {

    public string Text;
    public Texture2D PageTexture;

    public GUIStyle myGuiStyle = new GUIStyle();

    // If true, will only show once
    // If false, will show every time trigger area is entered
    public bool bShowOnlyOnce = false;

    // Show button at bottom of screen
    public bool bShowButton = true;

    private bool bShowNote = false;
    private Rect rectBmpBg;
    private Rect rectText;
    private Rect rectBtn;



    void Start() {

        if (myGuiStyle == null) {
            myGuiStyle.wordWrap = true;
        }

        rectBmpBg = MakeRectByPercent(0.7f,0.6f,TextAnchor.MiddleCenter);
        rectText = MakeRectByPercent(0.65f,0.45f,TextAnchor.MiddleCenter);
        rectBtn = new Rect(rectText.x+rectText.width/2-40,rectText.y+rectText.height-25,80,20);

    }

    void OnTriggerEnter(Collider target) {

        if (target.tag.Equals("Player")) {
            bShowNote = true;
            AudioSource mySfx = GetComponent<AudioSource>() as AudioSource;
            if (mySfx != null) audio.Play();
        }
    }

    void OnGUI() {

        if (!bShowNote) return;

        GUI.skin = GuiManager.Instance.myGuiSkin;

        // If you haven't added a page texture
        if (PageTexture == null) {
            GUI.Box(rectBmpBg,"");
        } else
            GUI.DrawTextureWithTexCoords(rectBmpBg,PageTexture,new Rect(0,0.6f,1,0.4f));

        GUI.Box(rectText, Text,myGuiStyle);

        // If escape, or enter or left click

        if (Input.GetKeyDown(KeyCode.Return)) bShowNote = false;
        if (Input.GetKeyDown(KeyCode.KeypadEnter)) bShowNote = false;
        if (Input.GetKeyDown(KeyCode.Escape)) bShowNote = false;

        if (bShowButton) {

            if (GUI.Button(rectBtn, "Resume") )
                bShowNote = false;

        } else {
            if (Input.GetMouseButtonDown(0)) bShowNote = false;
        }

    }
    public static Rect MakeRectByPercent(float x, float y, TextAnchor position) {


        if ((x > 1) || (y > 1)) {
            return new Rect(0,0,Screen.width,Screen.height);
        }

        x = Screen.width * x;
        y = Screen.height * y;

        return MakeRectByPixel(x,y,position);
    }


    // Returns a rectangle centered on the screen according to the positions below
    public static Rect MakeRectByPixel(float x, float y, TextAnchor position) {

        if (position == TextAnchor.MiddleCenter) {
            return new Rect(Screen.width/2-(x/2),Screen.height/2-(y/2),x,y);
        }

        if (position == TextAnchor.UpperCenter) {
            return new Rect(Screen.width/2-(x/2),0,x,y);
        }

        if (position == TextAnchor.LowerCenter) {
            return new Rect(Screen.width/2-(x/2),Screen.height-y,x,y);
        }

        if (position == TextAnchor.UpperLeft) {
            return new Rect(0,0,x,y);
        }

        if (position == TextAnchor.MiddleLeft) {
            return new Rect(0,Screen.height/2-(y/2),x,y);
        }

        if (position == TextAnchor.LowerLeft) {
            return new Rect(0,Screen.height-y,x,y);
        }

        if (position == TextAnchor.UpperRight) {
            return new Rect(Screen.width-x,0,x,y);
        }

        if (position == TextAnchor.MiddleRight) {
            return new Rect(Screen.width-x,Screen.height/2-(y/2),x,y);
        }

        if (position == TextAnchor.LowerRight) {
            return new Rect(Screen.width-x,Screen.height-y,x,y);
        }

        return new Rect(0,0,0,0);
    }
}