health box [2]

using UnityEngine;
using System.Collections;

[RequireComponent(typeof(AudioSource))]
public class HealthBox : MonoBehaviour
{
    public float addHealthVal = 10;
    public string userTag;
    public KeyCode key;

    public int countUse = 3;

    public AudioSource source;

    private bool isShowTooltip = false;

    public void OnTriggerEnter(Collider coll)
    {
        if (coll.gameObject.tag.Equals(userTag))
            isShowTooltip = true;
    }

    public void OnTriggerExit(Collider coll)
    {
        if (coll.gameObject.tag.Equals(userTag))
            isShowTooltip = false;
    }

    public void OnTriggerStay(Collider coll)
    {
        if (Input.GetKeyDown(key) && coll.gameObject.tag.Equals(userTag))
        {
            HealthUser health = coll.gameObject.GetComponent<HealthUser>();

            if (health.getHealth() >= 100)
                return;

            health.addHealth(addHealthVal);

            health = null;
            countUse--;

            source.Play();

            if (countUse < 1)
                Destroy(gameObject);
        }
    }

    public void OnGUI()
    {
        if (isShowTooltip)
        {
            GUI.Box(new Rect(100, 50, 100, 30), "THIS IS TOOLTIP HEALTH-BOX");
        }
    }
}