Unity GUI Scale

using UnityEngine;
using System.Collections;

public class MainMenuGUI : MonoBehaviour {

    //Variables
    public GUIStyle PlayButton;
    public GUIStyle OptionsButton;
    public GUIStyle InstructionsButton;
    public GUIStyle ExitButton;
    public Texture Background;
    bool doWindow0 = false;

    // Use this for initialization
    void Start () {

    }

    // Update is called once per frame
    void Update () {
        doWindow0 = false;
    }

    void OnGUI () {
        //GUI Matrix and GUI Scaling
        Vector3 scale;
        int originalWidth = 1600;
        int originalHeight = 770;

        scale.x = Screen.width/originalWidth;
        scale.y = Screen.height/originalHeight;
        scale.z = 1;
        Matrix4x4 svMat = GUI.matrix;
        GUI.matrix = Matrix4x4.TRS(new Vector3(0,0,0), Quaternion.identity, scale);

        //Start Matrix
        //Draw Background
        GUI.DrawTexture(new Rect(0,0,Screen.width,Screen.height),Background,ScaleMode.StretchToFill, false, 0.0f);
        //End Draw Background

        //Draw PlayButton
        if (GUI.Button(new Rect(30,180,235,590),"",PlayButton))
        {
            Application.LoadLevel("LoginScreen");
        }
        //End Draw PlayButton

        //Draw OptionsButton
        GUI.Button(new Rect(260,330,220,440),"",OptionsButton);
        //End Draw OptionsButton

        //Draw InstructionsButton
        if (GUI.Button(new Rect(1160,330,145,440),"",InstructionsButton))
        {
            doWindow0 = true;
        }
        //End Draw InstructionsButton

        //Draw ExitButton
        if (GUI.Button(new Rect(1320,180,265,590),"",ExitButton))
        {
            Application.Quit();
        }
        //End Draw ExitButton
        //End Matrix
        GUI.matrix = svMat;

        if (doWindow0 == true)
            GUI.Window (0, new Rect(Screen.width/2-240,Screen.height/2-100,800,120), DoMyWindow, "Instructions:");
    }

    void DoMyWindow (int windowID) {
        GUI.Label (new Rect (10, 20, 800, 40), "Welcome to RedLightLife! Use WASD keys to move your character and use KL to rotate the camera. Use the J key to interact with people and objects. To have your character jump use the SPACEBAR. To pause your game, press the P key.");
        if (GUI.Button (new Rect (10,80,100,20), "Close"))
            doWindow0 = false;
    }
}