light intensity control with slider

it’s my simple code,it has no error but not working
help me thanks!!

using UnityEngine;

using System.Collections;

public class Hslider : MonoBehaviour
{

public Light mylight;

private float myintensity = 1.0f;

private float Swidth = Screen.width;

private float Sheight = Screen.height;

void start()
{

}

void update()
{
	mylight.intensity = myintensity;
}

void OnGUI () 
{
	myintensity = GUI.HorizontalSlider (new Rect (Swidth/2f-150f, Sheight/1.1f, 300, 30), myintensity, 0.0f, 10.0f);
}

}

There’s a typo: it’s Update, not update - Unity is case sensitive, thus the function update will never be called (the same applies to Start)