using System;

namespace ConsoleColorProject
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine();
            Start();
        }

       static void Calculator()
        {
            string str;
            double firstNum;
            double secNum;
            char op;

            do
            {
                Console.WriteLine();
                Console.Write("First number: ");
                str = Console.ReadLine();

                if (str == "exit")
                {
                    Console.WriteLine();
                    Start();
                }

                firstNum = Convert.ToDouble(str);

                Console.Write("Operator: ");
                op = Convert.ToChar(Console.ReadLine());

                Console.Write("Second number: ");
                secNum = Convert.ToDouble(Console.ReadLine());

                double erg1 = firstNum + secNum;
                double erg2 = firstNum - secNum;
                double erg3 = firstNum * secNum;
                double erg4 = firstNum / secNum;

                switch (op)
                {
                    case '+': Console.WriteLine(erg1); break;
                    case '-': Console.WriteLine(erg2); break;
                    case '*': Console.WriteLine(erg3); break;
                    case '/': Console.WriteLine(erg4); break;
                }
                Console.WriteLine();

            } while (true);
        }


        static void Start()
        {
            Console.WriteLine("(Type in the number and press ENTER to select. Type in 'exit' after 'First Number' comes up to go back to the menu.)");
            Console.WriteLine("1) Background color");
            Console.WriteLine("2) Font color");
            Console.WriteLine("3) Start program");
            int x = Convert.ToInt32(Console.ReadLine());

            switch (x)
            {
                case 1: ConsoleBG(); break;
                case 2: ConsoleFG(); break;
                case 3: Calculator(); break;
            }
            Start();
        }

        static void ConsoleBG()
        {
            Console.WriteLine();
            Console.WriteLine("1) green, "+"2) yellow, "+"3) red, "+"4) darkblue, "+"5) back");
            int x = Convert.ToInt32(Console.ReadLine());

            switch (x)
            {
                case 1: Console.BackgroundColor = ConsoleColor.Green; break;
                case 2: Console.BackgroundColor = ConsoleColor.Yellow; break;
                case 3: Console.BackgroundColor = ConsoleColor.Red; break;
                case 4: Console.BackgroundColor = ConsoleColor.DarkBlue; break;
                case 5: Start(); break;
            }
            Console.Clear();
            Start();
        }


        static void ConsoleFG()
        {
            Console.WriteLine();
            Console.WriteLine("1) white, "+"2) black, "+"3) blue, "+"4) back");
            int x = Convert.ToInt32(Console.ReadLine());

            switch (x)
            {
                case 1: Console.ForegroundColor = ConsoleColor.White; break;
                case 2: Console.ForegroundColor = ConsoleColor.Black; break;
                case 3: Console.ForegroundColor = ConsoleColor.Blue; break;
                case 4: Start(); break;
            }
            Console.WriteLine();
            Start();
        }
    }
}