NumberGame

using System;

public class Program
{
    public static void Main()
    {
        Console.WriteLine("Input your age.");

        int ageMinimum = 18;
        int age = InputNumber();

        if (age < ageMinimum)
        {
            Console.WriteLine("Your age too small than 18.");
        }
        else
        {
            Console.WriteLine("You're welcome.");
            PlayNumberGame();
        }
    }

    public static int InputNumber()
    {
        int number;
        bool isInput;

        do
        {
            isInput = !int.TryParse(Console.ReadLine(), out number);
        }
        while(isInput);

        return number;
    }

    public static void PlayNumberGame()
    {
        int numberMinimum = 0;
        int numberMaximum = 100;
        Random random = new Random();
        bool isPlaying = true;

        int numberChoose;
        int numberRandom;

        do
        {
            PrintMenu();
            numberChoose = InputNumber();

            switch(numberChoose)
            {
                case 0:
                    numberRandom = random.Next(numberMinimum, numberMaximum);
                    Console.WriteLine("Input a number from " + numberMinimum + " to " + numberMaximum + ".");
                    numberChoose = InputNumber();

                    if (numberChoose == numberRandom)
                        Console.WriteLine("You win!!!!");
                    else
                        Console.WriteLine("You loose.");
                break;
                case 1:
                    isPlaying = false;
                    Console.WriteLine("Exit from game.");
                break;
            }
        }
        while (isPlaying);
    }


    public static void PrintMenu()
    {
        Console.WriteLine("\n0. Play Number Game.");
        Console.WriteLine("1. Exit.");
    }
}