i wanted to add Count down time in Tanks Game

how to add Countdown timer in Tanks Game, There will be time limit in each round so what should i do and in which script i have to modify ?

@username

There is a public parameter with the name targetTime. Before starting your round or level assign the targetTime for each round.
It would be a better if you use the observer technique to send callbacks to other scripts on targetTime zero.
Keep the timer code in the GAMESTATE manager class it will keep track how much time passed and your remaining time for round.

using UnityEngine;
using System.Collections;

public class Timer : MonoBehaviour
{

	public float targetTime;

	void Update ()
	{
			if (targetTime >= 0) {
				targetTime -= Time.deltaTime;
			} 

		string timer = ToHourseMinutesSeconds (targetTime);
		if (targetTime <= 0) {
            // Show your objective failed or anything else
		}
		TimeText.text = timer;
	}
	public static string ToHourseMinutesSeconds (float seconds)
	{
		float s = seconds % 60;
		float ms = s * 1000;
		
		ms = ms % 100;
		int m = (int)seconds / 60;
		int h = (int)m / 60;
		
		string secondsDots = " ";
		secondsDots = ":";
		return ToDualDigit (m) + ":" + ToDualDigit ((int)s);
		
	}
}