Memory implemented in C#

Memory.cs

using System;

namespace Memory
{
	class Program
	{
		/// <summary>
		/// Motives of the pairs
		/// </summary>
		private static char[] displaySymbols = { '@', '☺', '☻', '●', 'Ⱡ', '♫', '♪', '♦', '♥', '♣', '♠', '♂', '♀', '☼', '█', '▲', '℗', 'Ω' };

		/// <summary>
		/// Size of the play field
		/// </summary>
		private static int size = 4;

		static void Main(string[] args)
		{
			//Represents where each pair is located. This should only be read from during gameplay, not being written to
			char[,] gameArray = new char[size, size];

			//Represents what the player sees. Should only be written to and not being read from during gameplay
			char[,] displayArray = new char[size, size];

			PrintWelcome();
			FillGameArray(gameArray);
			FillDisplayArray(displayArray, '?');

			PlayGame(gameArray, displayArray);
		}

		/// <summary>
		/// Prints a welcome message
		/// </summary>
		private static void PrintWelcome()
		{
			Console.WriteLine("Herzlich Willkommen zu meinem Memory Spiel");
			Console.WriteLine("------------------------------------------");
			Console.WriteLine("Bitte geben Sie jeweils 2 Koordinaten ein, die Sie vergleichen wollen.");
			Console.WriteLine("z.B.: 3132 vergleicht (3,1) mit (3,2)");
			Console.WriteLine();
		}

		/// <summary>
		/// Fills the gameArray with pairs of symbols
		/// </summary>
		/// <param name="gameArray">The array containing the pairs</param>
		private static void FillGameArray(char[,] gameArray)
		{
			int x;
			int y;
			Random random = new Random();

			for (int pairs = 0; pairs < (size*size)/2; pairs++)
			{
				for (int i = 0; i < 2; i++)
				{
					do
					{
						x = random.Next(size);
						y = random.Next(size);
					} while (gameArray[x, y] != 0);
					gameArray[x, y] = displaySymbols[pairs];
				}
			}
		}

		/// <summary>
		/// Fills the displayArray with placeholder characters
		/// </summary>
		/// <param name="displayArray">The array which the player sees</param>
		/// <param name="placeholder">The placeholder indicating a "face-down" card</param>
		private static void FillDisplayArray(char[,] displayArray, char placeholder)
		{
			for (int y = 0; y < size; y++)
			{
				for (int x = 0; x < size; x++)
				{
					displayArray[x, y] = placeholder;
				}
			}
		}

		/// <summary>
		/// The main loop for the game
		/// </summary>
		/// <param name="gameArray">The array containing all the pairs</param>
		/// <param name="displayArray">The array which the user sees</param>
		private static void PlayGame(char[,] gameArray, char[,] displayArray)
		{
			//TODO: Implementiere das Spiel Memory
			//Tipp: Wenn du Probleme hast, sieh dir dazu meine Musterlösung an.
		}
	}
}