How can I display a Menu and HUD on a mobile game?

I want to display some life info and other menu options, how should I do this? I tried using OnGUI, but it wouldn’t change size on my mobile device. Are there any other alternatives?

You need to put a little bit of work into it to change size. I’ll give a very simple example in C#.

using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour 
{
	Rect rect;
	string label = "GUI Box";
	
	void Update()
	{
		//My original box is 256 x 256 pixels in 1366 x 768 resolution. 
		//I Divide 1366 by 256 to get 5.34. Then I divide Screen width by this sum to keep the aspect ratio.
		//I do the same with the height. 768 / 256 = 3, so Screen.height / 3 to keep aspect.
		//This will keep the box the correct size no matter what device or res you're using.  
		if(rect != new Rect(0, 0, Screen.width / 5.34f, Screen.height / 3))
			rect = new Rect(0, 0, Screen.width / 5.34f, Screen.height / 3);
	}
	
	void OnGUI()
	{
		GUI.Box(rect, label);
	}
}