Ứng dụng lớp điểm ký tự xây dựng trò chơi bắn chữ

CDIEM.cs

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

namespace bt18
{
   class CDIEM
    {
        private int x;
        private int y;
        public char c;

        public CDIEM()
        {
        }

        public CDIEM(int xx, int yy, char cc)
        {
            x = xx;
            y = yy;
            c = cc;
        }

        public bool KiemTraX(int xx)
        {
            if (xx <= 0 || xx >= Console.WindowWidth)
            {
                return false;
            }
            return true;
        }
        public bool KiemTraY(int yy)
        {
            if (yy <= 0 || yy >= Console.WindowHeight)
            {
                return false;
            }
            return true;
        }

        public void DichPhai(int k)
        {
            x += k;
        }
        public void DichTrai(int k)
        {
            x -= k;
        }
        public void DichLen(int k)
        {
            y -= k;
        }
        public void DichXuong(int k)
        {
            y += k;
        }

        public void Xuat()
        {
            Console.SetCursorPosition(x, y);
            Console.Write(c);
        }

        public void Xoa()
        {
            Console.Clear();
        }

        public float KhoangCach(CDIEM M)
        {
            return 0;
        }
        public int KhoangCachX()
        {
            return x;
        }
        public int KhoangCachY()
        {
            return y;
        }

    }
}  

Program.cs

using System;
using System.Collections.Generic;
using System.Text;
using System.Threading;
using System.Collections;
namespace bt18
{
    class Program
    {
        static ArrayList list = new ArrayList();
        static Random rnd = new Random();
        static int TOCDO = 700;

        static void Main(string[] args)
        {
            Console.CursorVisible = false;
            do
            {
                NhanPhimBam();
                TaoChu();
                RoiChu();             
                Thread.Sleep(TOCDO);
            } while (KiemTraTiepTuc());         
        }

        static void RoiChu()
        {         
            Console.Clear();
            for (int i = 0; i < list.Count; i++)
            {
                ((CDIEM)list[i]).DichXuong(1);
                ((CDIEM)list[i]).Xuat();
            }
         
        }

        static void TaoChu()
        {
            char c;
            //do
            //{
            //    c = (char)(rnd.Next(65, 90));
            //} while(KiemTraChuTonTai(c));
            c = (char)(rnd.Next(65, 90));
            list.Add(new CDIEM(rnd.Next(1, Console.WindowWidth - 1), 0, c));
        }

        static bool KiemTraTiepTuc()
        {
            if (((CDIEM)list[0]).KhoangCachY() > Console.WindowHeight)
                return false;
            return true;
        }

        static void NhanPhimBam()
        {         
            while (Console.KeyAvailable)
            {
                char cc = Console.ReadKey(true).KeyChar;

                for (int i = 0; i < list.Count; i++)
                {
                    if (((CDIEM)list[i]).c == cc)
                    {
                        list.RemoveAt(i);
                    }
                }

            }            
        }
    }
}