C#-Code

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace TYP217 {
  enum Color { Red, Blue, Yellow, Green, White, Magenta, Cyan, DarkCyan }

  class Program {
    static readonly int[] colorMap = new int[] {
      (int)ConsoleColor.Red, (int)ConsoleColor.Blue, (int)ConsoleColor.Yellow,
      (int)ConsoleColor.Green, (int)ConsoleColor.White, (int)ConsoleColor.Magenta,
      (int)ConsoleColor.Cyan, (int)ConsoleColor.DarkCyan
    };
    static readonly Color maxC = (Color)6; //Enum.GetValues(typeof(Color)).Cast<Color>().Max();
    const int codeLength = 4;
    const char colorChar = (char)219;

    static void Main() {
      Console.OutputEncoding = Encoding.GetEncoding(1252);
      Console.Clear();
      Console.Write((new StringBuilder()).Append("\n-").Append('-', codeLength * 3));

      Color[] input = null;
      Color[] code = GetCode();

      for(int round = 0; round < 16; round++) {
        input = ReadInput(round, input);
        int same = CountSamePos(code, input);
        if(codeLength == same) {
          DrawHint(round, same, 0);
          break;
        }
        
        int diff = CountDiffPos(code, input);
        DrawHint(round, same, diff);
      }

      DrawCode(code);
      Console.ReadKey(true);
    }

    static Color[] ReadInput(int round, Color[] colors = null) {
      Color[] input = new Color[codeLength];
      Console.CursorTop = 17 - round;
      Console.CursorLeft = 0;

      for(int i = 0; i < codeLength; i++) {
        input[i] = colors?[i] ?? 0;
        Console.ForegroundColor = (ConsoleColor)colorMap[(int)input[i]];
        Console.Write(colorChar);
        Console.CursorLeft++;
      }

      Console.CursorLeft = 0;
      ConsoleKey key;
      do {
        key = Console.ReadKey(true).Key;
        int i = Console.CursorLeft / 2;

        if(key == ConsoleKey.UpArrow || key == ConsoleKey.DownArrow) {
          if(key == ConsoleKey.UpArrow) {
            input[i] = input[i] == maxC ? input[i] = 0 : input[i] + 1;
          } else {
            input[i] = input[i] == 0 ? input[i] = maxC : input[i] - 1;
          }

          Console.ForegroundColor = (ConsoleColor)colorMap[(int)input[i]];
          Console.Write(colorChar);
          Console.CursorLeft--;
        }

        int cursorMax = (codeLength * 2) - 2;
        if(key == ConsoleKey.LeftArrow || key == ConsoleKey.RightArrow) {
          if(key == ConsoleKey.LeftArrow) {
            Console.CursorLeft = Console.CursorLeft == 0 ? cursorMax : Console.CursorLeft - 2;
          } else {
            Console.CursorLeft = Console.CursorLeft == cursorMax ? 0 : Console.CursorLeft + 2;
          }
        }
      } while(key != ConsoleKey.Enter);

      Console.CursorLeft = 0;
      Console.ResetColor();

      return input;
    }

    static Color[] GetCode() {
      Random rnd = new Random();
      Color[] code = new Color[codeLength];
      for(int i = 0; i < codeLength; i++) code[i] = (Color)rnd.Next((int)maxC);

      return code;
    }

    static int CountSamePos(Color[] a, Color[] b) {
      if(a.Length != b.Length) throw new Exception();

      int result = 0;
      for(int i = 0; i < a.Length; i++) {
        if(a[i] == b[i]) result++;
      }

      return result;
    }

    static int CountDiffPos(Color[] a, Color[] b) {
      if(a.Length != b.Length) throw new Exception();
      List<Color> aDiff = new List<Color>();
      List<Color> bDiff = new List<Color>();
      for(int i = 0; i < a.Length; i++) {
        if(a[i] != b[i]) {
          aDiff.Add(a[i]);
          bDiff.Add(b[i]);
        }
      }

      int result = 0;
      foreach(Color color in aDiff.Concat(bDiff).Distinct()) {
        result += Math.Min(aDiff.Count(x => x == color), bDiff.Count(x => x == color));
            
      }

      return result;
    }

    static void DrawHint(int round, int same, int diff) {
      StringBuilder sb = new StringBuilder();
      Console.CursorTop = 17 - round;
      Console.CursorLeft = codeLength * 2;
      Console.BackgroundColor = ConsoleColor.White;

      Console.ForegroundColor = ConsoleColor.Black;
      Console.Write(sb.Append('*', same));
      sb.Clear();
      Console.ForegroundColor = ConsoleColor.Red;
      Console.Write(sb.Append('*', diff));

      while(Console.CursorLeft <= codeLength * 3) Console.Write(' ');

      Console.ResetColor();
    }

    static void DrawCode(Color[] code) {
      Console.CursorTop = 0;
      Console.CursorLeft = 0;

      for(int i = 0; i < codeLength; i++) {
        Console.ForegroundColor = (ConsoleColor)colorMap[(int)code[i]];
        Console.Write(colorChar);
        Console.CursorLeft++;
      }

      Console.ResetColor();
    }
  }
}

C#-Code

using System;
using static System.Console;
using System.Collections.Generic;
using System.Text;

namespace aufgabe_217_mastermind
{
    class Program
    {
        static void Main()
        {
            Random rand = new Random();
            bool bo_break = false;
            while (!bo_break)
            {
                Clear(); // = Console.Clear();
                int[] code = new int[] { rand.Next(6), rand.Next(6), rand.Next(6), rand.Next(6) };                
                int[] move = new int[4];
                Class_Mastermind cm = new Class_Mastermind(code);
                //Write(cm.getsecret());
                bool bo_game_runs = true;
                int counter = 0, max_counter = 10;
                bool bo_end1 = false;
                bool bo_end2 = false;
                while (bo_game_runs)
                {                    
                    bool bo_input_okay = false;
                    while (!bo_input_okay)
                    {
                        bo_input_okay = true;
                        Write($"give me your move (e.g. 0124 or 11 (is interpreted as 0011) or 0 (= 0000)): ");
                        int input;
                        bo_input_okay = int.TryParse(ReadLine(), out input);

                        for (var i = 0; i < move.Length; i++)
                        {
                            move[move.Length - 1 - i] = input % 10;
                            input /= 10;
                            if (move[i] > 5)
                                bo_input_okay = false;
                        }
                    }
                    counter++;
                    Clear();

                    bo_end1 = !cm.play(move);
                    bo_end2 = counter < max_counter;

                    bo_game_runs = bo_end1 && bo_end2;
                    Write(cm.movelist(bo_with_secret: false));
                }

                string info = "you have lost";
                if(!bo_end1)
                    info = "you have won";

                WriteLine($"game over: {info}{Environment.NewLine}code was {cm.getsecret()}");
                WriteLine("new game? (n = EXIT)");

                ConsoleKeyInfo ki = ReadKey(false);
                bo_break = ki.Key == ConsoleKey.N;
            }
        }
    }

    public class Class_Mastermind
    {
        int array_length;
        int[] secret;

        List<int[]> moves = new List<int[]>();

        public Class_Mastermind(int[] code)
        {
            this.array_length = code.Length;
            this.secret = new int[code.Length];
            code.CopyTo(this.secret, 0);
        }

        public bool play(int[] move)
        {
            bool bo_result = true;
            int[] temp = new int[array_length + 2];            
            for (var i = 0; i < move.Length; i++)
            {
                if (move[i] != secret[i])
                    bo_result = false;                
                temp[i + 1] = move[i];
            }
            int[] temp1 = number_of_black_and_white(secret, move);
            temp[0] = temp1[0];
            temp[temp.Length - 1] = temp1[1];
            moves.Add(temp);
            return bo_result; //true: game over
        }

        public string movelist(bool bo_with_secret = false)
        {
            StringBuilder sb = new StringBuilder();
            string sadd = string.Empty;
            for (var i = 0; i < moves.Count; i++)
            {
                if (bo_with_secret)
                    sadd = getsecret();
                sb.Append(sadd + $"{moves[i][0], 2} :");
                for (var j = 1; j < moves[i].Length - 1; j++)
                    sb.Append($"{moves[i][j], 2}");
                sb.AppendLine($" :{moves[i][moves[i].Length - 1], 2}");               
            }
            return sb.ToString();
        }

        public string getsecret()
        {
            StringBuilder sb = new StringBuilder("    ");
            for (var j = 0; j < secret.Length; j++)
                sb.Append($"{secret[j],2}");
            sb.AppendLine();
            return sb.ToString();
        }

        int[] number_of_black_and_white(int[] n, int[] ns) //according to DONALD E. KNUTH; n = code; ns = pattern
        {
            int[] result_ncode = new int[n.Length + 2];//total_number_of_hits
            int[] result_ntest = new int[ns.Length + 2];//total_number_of_misses
            int counter_black = 0;
            for (var i = 0; i < ns.Length; i++)
            {
                if (ns[i] == n[i])
                    counter_black++;

                result_ncode[ns[i]]++;
                result_ntest[n[i]]++;
            }

            int[] result = new int[2];
            for (var i = 0; i < this.array_length + 2; i++)
                result[0] += Math.Min(result_ncode[i], result_ntest[i]);
            result[1] = result[0] - counter_black;
            result[0] = counter_black;
            return result;
        }
    }
}

C#-Code

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace MasterMind
{
    class Game
    {
        private static String userSecretCode,
                              message = "\nYou lost.";
        private static int counter = 12;
        private static String title = "MasterMind v1.0 - ";
        static void Main(string[] args)
        {
            Console.ForegroundColor = ConsoleColor.Green;
            /*-------------------------------------------------------------*/
            SecretCode sc = new SecretCode();
            for (int i = 0; i < counter; i++)
            {
                Console.Title = title + (counter - i) + " tries left.";
                try
                {
                    sc.verifySecretCode((userSecretCode = Console.ReadLine()));
                    if (userSecretCode != sc.secretCode)
                        sc.handleUserSecretCode(userSecretCode);
                    else
                    {
                        message = "You won.";
                        break;
                    }
                }
                catch (SecretCodeFormatException e)
                {
                    Console.WriteLine(e.Message);
                    i--;
                    continue;
                }
            }
            Console.WriteLine(message + " The code was " + sc.secretCode);
        }
        public class SecretCode
        {
            public String secretCode { get; }
            public SecretCode()
            {
                secretCode = createSecretCode();
            }
            public String createSecretCode()
            {
                Random rand = new Random();
                return rand.Next(1, 7).ToString() + rand.Next(1, 7) + rand.Next(1, 7) + rand.Next(1, 7).ToString();
            }
            public void handleUserSecretCode(String pUserSecretCode)
            {
                int count = 0, //right number
                    count1 = 0; ; //right number on right spot
                for(int i = 0; i < 4; i++)
                {
                    if (pUserSecretCode[i] == secretCode[i])
                    {
                        count1++;
                    }
                    else
                    {
                        if(pUserSecretCode.Substring(i).Contains(secretCode[i]))
                            count++;
                    }
                }
                Console.WriteLine(count + "hits.\n" + count1 + " perfect matches.\n");
            }
            public void verifySecretCode(String pUserSecretCode)
            {
                /*Requirements
                 * Length = 4
                 * Numbers only
                 * Highest Value = 6, Lowest Value = 1
                 */
                if (pUserSecretCode.Length == 4)
                {
                    foreach (char c in pUserSecretCode)
                    {
                        try
                        {
                            int n = Convert.ToInt32(c.ToString());
                            if (n < 1)
                                throw new SecretCodeFormatException("Values are lower than 1!");
                            else if (n > 6)
                                throw new SecretCodeFormatException("Values are higher than 6!");
                        }
                        catch (FormatException) { throw new SecretCodeFormatException("Numbers only!"); }
                    }
                }
                else
                    throw new SecretCodeFormatException("SecretCode must be 4 characters!");
            }
        }
        public class SecretCodeFormatException : Exception
        {
            public SecretCodeFormatException(string message) : base("\n"+message+"\n")
            {
                
            }
        }
    }
}