Added proprietary user interface.

Added most game logic.

CleanTicTacToe/Properties/Grid.cs

@@ -1,26 +0,0 @@
-namespace TicTacToe {
-    public class Grid {
-        private readonly Player[,] _field;
-        private const int GRIDSIZE = 3;
-        public bool GameOver => IsGameOver();
-
-        private bool IsGameOver() {
-            for (var x = 0; x < GRIDSIZE; x++)
-                for (var y = 0; y < GRIDSIZE; y++)
-                    if (IsFieldEmpty(x, y))
-                        return false;
-            return true;
-        }
-
-        private bool IsFieldEmpty(int x, int y) {
-            return _field[x, y] == Player.Empty;
-        }
-
-        public Grid() {
-            _field = new Player[GRIDSIZE, GRIDSIZE];
-        }
-
-        public bool PickSpot() {
-        }
-    }
-}

CleanTicTacToe/Properties/Player.cs

@@ -1,7 +0,0 @@
-namespace TicTacToe {
-    enum Player {
-        Empty = 0,
-        Cross = 1,
-        Circle = 2
-    }
-}