diff --git a/54_Letter/csharp/Game.cs b/54_Letter/csharp/Game.cs
new file mode 100644
index 00000000..e7d525c9
--- /dev/null
+++ b/54_Letter/csharp/Game.cs
@@ -0,0 +1,137 @@
+namespace Letter
+{
+    internal static class Game
+    {
+        /// <summary>
+        /// Maximum number of guesses.
+        /// Note the program doesn't enforce this - it just displays a message if this is exceeded.
+        /// </summary>
+        private const int MaximumGuesses = 5;
+
+        /// <summary>
+        /// Main game loop.
+        /// </summary>
+        public static void Play()
+        {
+            DisplayIntroductionText();
+
+            // Keep playing forever, or until the user quits.
+            while (true)
+            {
+                PlayRound();
+            }
+        }
+
+        /// <summary>
+        /// Play a single round.
+        /// </summary>
+        internal static void PlayRound()
+        {
+            var gameState = new GameState();
+            DisplayRoundIntroduction();
+
+            char letterInput = '\0'; // Set the initial character to something that's not A-Z.
+            while (letterInput != gameState.Letter)
+            {
+                letterInput = GetCharacterFromKeyboard();
+                gameState.GuessesSoFar++;
+                DisplayGuessResult(gameState.Letter, letterInput);
+            }
+            DisplaySuccessMessage(gameState);
+        }
+
+        /// <summary>
+        /// Display an introduction when the game loads.
+        /// </summary>
+        internal static void DisplayIntroductionText()
+        {
+            Console.ForegroundColor = ConsoleColor.Yellow;
+            Console.WriteLine("LETTER");
+            Console.WriteLine("Creative Computing, Morristown, New Jersey.");
+            Console.WriteLine("");
+
+            Console.ForegroundColor = ConsoleColor.DarkGreen;
+            Console.WriteLine("Letter Guessing Game");
+            Console.WriteLine("I'll think of a letter of the alphabet, A to Z.");
+            Console.WriteLine("Try to guess my letter and I'll give you clues");
+            Console.WriteLine("as to how close you're getting to my letter.");
+            Console.WriteLine("");
+
+            Console.ResetColor();
+        }
+
+        /// <summary>
+        /// Display introductionary text for each round.
+        /// </summary>
+        internal static void DisplayRoundIntroduction()
+        {
+            Console.ForegroundColor = ConsoleColor.Yellow;
+            Console.WriteLine("O.K., I have a letter. Start guessing.");
+
+            Console.ResetColor();
+        }
+
+        /// <summary>
+        /// Display text depending whether the guess is lower or higher.
+        /// </summary>
+        internal static void DisplayGuessResult(char letterToGuess, char letterInput)
+        {
+            Console.BackgroundColor = ConsoleColor.White;
+            Console.ForegroundColor = ConsoleColor.Black;
+            Console.Write(" " + letterInput + " ");
+
+            Console.ResetColor();
+            Console.ForegroundColor = ConsoleColor.Gray;
+            Console.Write(" ");
+            if (letterInput != letterToGuess)
+            {
+                if (letterInput > letterToGuess)
+                {
+                    Console.WriteLine("Too high. Try a lower letter");
+                }
+                else
+                {
+                    Console.WriteLine("Too low. Try a higher letter");
+                }
+            }
+            Console.ResetColor();
+        }
+
+        /// <summary>
+        /// Display success, and the number of guesses.
+        /// </summary>
+        internal static void DisplaySuccessMessage(GameState gameState)
+        {
+            Console.ForegroundColor = ConsoleColor.Green;
+            Console.WriteLine($"You got it in {gameState.GuessesSoFar} guesses!!");
+            if (gameState.GuessesSoFar > MaximumGuesses)
+            {
+                Console.ForegroundColor = ConsoleColor.Red;
+                Console.WriteLine($"But it shouldn't take more than {MaximumGuesses} guesses!");
+            }
+            else
+            {
+                Console.WriteLine("Good job !!!!!");
+            }
+            Console.ForegroundColor = ConsoleColor.Yellow;
+            Console.WriteLine("");
+            Console.WriteLine("Let's play again.....");
+
+            Console.ResetColor();
+        }
+
+        /// <summary>
+        /// Get valid input from the keyboard: must be an alpha character. Converts to upper case if necessary.
+        /// </summary>
+        internal static char GetCharacterFromKeyboard()
+        {
+            char letterInput;
+            do
+            {
+                var keyPressed = Console.ReadKey(true);
+                letterInput = Char.ToUpper(keyPressed.KeyChar); // Convert to upper case immediately.
+            } while (!Char.IsLetter(letterInput)); // If the input is not a letter, wait for another letter to be pressed.
+            return letterInput;
+        }
+    }
+}
diff --git a/54_Letter/csharp/GameState.cs b/54_Letter/csharp/GameState.cs
new file mode 100644
index 00000000..02aa38b1
--- /dev/null
+++ b/54_Letter/csharp/GameState.cs
@@ -0,0 +1,37 @@
+namespace Letter
+{
+    /// <summary>
+    /// Holds the current state.
+    /// </summary>
+    internal class GameState
+    {
+        /// <summary>
+        /// Initialise the game state with a random letter.
+        /// </summary>
+        public GameState()
+        {
+            Letter = GetRandomLetter();
+            GuessesSoFar = 0;
+        }
+
+        /// <summary>
+        /// The letter that the user is guessing.
+        /// </summary>
+        public char Letter { get; set; }
+
+        /// <summary>
+        /// The number of guesses the user has had so far.
+        /// </summary>
+        public int GuessesSoFar { get; set; }
+
+        /// <summary>
+        /// Get a random character (A-Z) for the user to guess.
+        /// </summary>
+        internal static char GetRandomLetter()
+        {
+            var random = new Random();
+            var randomNumber = random.Next(0, 26);
+            return (char)('A' + randomNumber);
+        }
+    }
+}
diff --git a/54_Letter/csharp/Program.cs b/54_Letter/csharp/Program.cs
new file mode 100644
index 00000000..9a1c29db
--- /dev/null
+++ b/54_Letter/csharp/Program.cs
@@ -0,0 +1,3 @@
+using Letter;
+
+Game.Play();
\ No newline at end of file