Hi everyone, I'm a newbie to unity3d and programming in general. just started a few weeks ago and i'm still trying to figure things out. Right now I'm following a book on unity3d and I've stumbled on something strange that you might be able to help me with.. This is the code I'm using to create a button and place it in the center of the screen:

var customSkin:GUISkin;

var buttonW:int = 100;

var buttonH:int = 50;

private var halfScreenW:float = Screen.width/2;

private var halfButtonW:float = buttonW/2;

function OnGUI(){

    GUI.skin=customSkin;

    if(GUI.Button(Rect(halfScreenW,560,buttonW,buttonH),"Play Game"))

    {
        print("You clicked me!");
    }
}

One thing I've noticed is that when I replace "halfScreenW" with the actual value of the private var, "Screen.width/2", I get a different result than if I use the var name.. so the button's x value is different.. can someone tell me why this is and how to solve it?..

I've also noticed this with simple scripts like values multiplied by Time.deltaTime.. I would get a different result if I use a var as opposed to inputing an actual number.. Any help/explanation is highly appreciated!