Problemino snake in c#

[Yovecio]

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Linq;
using System.Text;
using System.Drawing;
using System.Windows.Forms;



namespace TurboSnake
{
    public partial class gamefrm : Form
    {
        public gamefrm()
        {
            
            InitializeComponent();
        }
        private Random gen = new Random();
        private int punteggio=0,livello=1,bonus=0,vite=3,xmela,ymela,xserp,yserp;
        private List<Point> ciccio = new List<Point>();
        private List<PictureBox> corpo=new List<PictureBox>(); 
        private void gamefrm_Load(object sender, EventArgs e)
        {
            serpenteimg.Location = new Point(10, 10);
            punteggiolbl.Text = Convert.ToString(punteggio);
            livellolbl.Text = Convert.ToString(livello);
            vitelbl.Text = Convert.ToString(vite);
            do
            {
                xmela = gen.Next(64 - 1) * 10;//genero posiione iniz. mela
                ymela = gen.Next(47 - 1) * 10;
            } while (ymela == serpenteimg.Location.Y && xmela == serpenteimg.Location.X);
            melaimg.Location = new Point(xmela, ymela);
            ciccio.Add(new Point(5,5));//aggiunta la testa
            ciccio.Add(new Point(5,8));//aggiunto corpo
            ciccio.Add(new Point(5,11));//aggiunto corpo
            ciccio.Add(new Point(5,14));//aggiunta coda
            for (int i = 0; i < ciccio.Count; i++)
            {
                PictureBox box=new PictureBox();// creo le immagini per il snake iniziali
                corpo.Add(box);
            }
            disegna();
        }
        
        private bool su = false, giu = false, dx = false, sx = false;
        private void gamefrm_KeyDown(object sender, KeyEventArgs e)
        {
            if (e.KeyCode == Keys.Up)//intercetto tasto su
            {
                timer2.Enabled = false;
                timer3.Enabled = false;
                timer4.Enabled = false;
                timer1.Interval = 30;
                timer1.Enabled = true;
                if (su == false)
                {
                    timer1.Tick += new EventHandler(timer1_Tick);
                    su = true; 
                }
            }
            if (e.KeyCode == Keys.Down)//intercetto tasto giu
            {
                timer1.Enabled = false;
                timer3.Enabled = false;
                timer4.Enabled = false;
                timer2.Interval =30;
                timer2.Enabled = true;
                if (giu == false)
                {
                    giu = true; 
                    timer2.Tick += new EventHandler(timer2_Tick);
                }
            }
            if (e.KeyCode == Keys.Left)//intercetto tasto sin
            {
                timer1.Enabled = false;
                timer2.Enabled = false;
                timer4.Enabled = false;
                timer3.Interval =30;
                timer3.Enabled = true;
                if (sx == false)
                {
                    sx = true;
                    timer3.Tick += new EventHandler(timer3_Tick);
                }
            }
            if (e.KeyCode == Keys.Right)//intercetto tasto destr
            {
                timer1.Enabled = false;
                timer2.Enabled = false;
                timer3.Enabled = false;
                timer4.Interval =30;
                timer4.Enabled = true;
                if (dx == false)
                {
                    dx = true;
                    timer4.Tick += new EventHandler(timer4_Tick); 
                }
            }
        }
        private void timer1_Tick(object sender, EventArgs e)
        {
            xserp=ciccio[0].X;yserp=ciccio[0].Y;
            yserp-= 3;
            ciccio.Insert(0, new Point(xserp, yserp));//movimento
            ciccio.RemoveAt(ciccio.Count-1);
            disegna();
           mela_mang();
        }
        private void timer2_Tick(object sender, EventArgs e)
        {
            xserp=ciccio[0].X;yserp = ciccio[0].Y;
            yserp += 3;
            ciccio.Insert(0, new Point(xserp, yserp));//movimento
            ciccio.RemoveAt(ciccio.Count - 1);
            disegna();
            mela_mang();
        }
        private void timer3_Tick(object sender, EventArgs e)
        {
            xserp = ciccio[0].X;yserp= ciccio[0].Y;
            xserp -= 3;
            ciccio.Insert(0, new Point(xserp, yserp));//movimento
            ciccio.RemoveAt(ciccio.Count - 1);
            disegna();
           mela_mang();
        }
        private void timer4_Tick(object sender, EventArgs e)
        {
            xserp = ciccio[0].X; yserp=ciccio[0].Y;
            xserp += 3;
            ciccio.Insert(0, new Point(xserp, yserp));//movimento
            ciccio.RemoveAt(ciccio.Count - 1);
            disegna();
           mela_mang();
        }
        private void aggiungi()
        {
            PictureBox box = new PictureBox();
            corpo.Add(box);  
        }

        private void disegna()//assegno ogni punto un immagine
        {
           for(int i=0;i<ciccio.Count;i++)
           {
               corpo[i].Location=ciccio[i];
               corpo[i].Size=new Size(20,20);
               corpo[i].BackColor = Color.LawnGreen;
               corpo[i].Visible = true;
               Controls.Add(corpo[i]);
               corpo[i].BringToFront();
               
           }
        }
        private void mela_mang()
        {
            if(melaimg.Bounds.IntersectsWith(corpo[0].Bounds))// se mangia mela
            {
                punteggio += 5;
                punteggiolbl.Text = Convert.ToString(punteggio);
                xmela = gen.Next(10, terrenopnl.Width - 20);
                ymela = gen.Next(10, terrenopnl.Height - 20);
                melaimg.Location = new Point(xmela, ymela);
                Application.DoEvents();// refresh form mela
                incrementa_serp();
                if (punteggio % 20 == 0)
                    livello++;
                livellolbl.Text = Convert.ToString(livello);
            }
        }
        private void incrementa_serp()
        {  
            if (su == true)
            {
                xserp = ciccio[ciccio.Count - 1].X; yserp = ciccio[ciccio.Count - 1].Y;
                ciccio.Add(new Point(xserp, yserp));//aggiunga 1# tassello
                xserp = ciccio[0].X; yserp = ciccio[0].Y;
                yserp += 3;
                ciccio.Add(new Point(xserp, yserp));
                ciccio.RemoveAt(ciccio.Count - 1);//spostamento
                aggiungi();
                disegna();

                xserp = ciccio[ciccio.Count - 1].X; yserp = ciccio[ciccio.Count - 1].Y;
                ciccio.Add(new Point(xserp, yserp));//aggiunga 2# tassello
                xserp = ciccio[0].X; yserp = ciccio[0].Y;
                yserp += 3;
                ciccio.Add(new Point(xserp, yserp));
                ciccio.RemoveAt(ciccio.Count - 1);//spostamento
                aggiungi();
                disegna();

                xserp = ciccio[ciccio.Count - 1].X; yserp = ciccio[ciccio.Count - 1].Y;
                ciccio.Add(new Point(xserp, yserp));//aggiunga 3# tassello
                xserp = ciccio[0].X; yserp = ciccio[0].Y;
                yserp += 3;
                ciccio.Add(new Point(xserp, yserp));
                ciccio.RemoveAt(ciccio.Count - 1);//spostamento
                aggiungi();
                disegna();
            }
            if (giu == true)
            {
                xserp = ciccio[ciccio.Count - 1].X; yserp = ciccio[ciccio.Count - 1].Y;
                ciccio.Add(new Point(xserp, yserp));//aggiunga 1# tassello
                xserp = ciccio[0].X; yserp = ciccio[0].Y;
                yserp -= 3;
                ciccio.Add(new Point(xserp, yserp));
                ciccio.RemoveAt(ciccio.Count - 1);//spostamento
                aggiungi();
                disegna();

                xserp = ciccio[ciccio.Count - 1].X; yserp = ciccio[ciccio.Count - 1].Y;
                ciccio.Add(new Point(xserp, yserp));//aggiunga 2# tassello
                xserp = ciccio[0].X; yserp = ciccio[0].Y;
                yserp -= 3;
                ciccio.Add(new Point(xserp, yserp));
                ciccio.RemoveAt(ciccio.Count - 1);//spostamento
                aggiungi();
                disegna();

                xserp = ciccio[ciccio.Count - 1].X; yserp = ciccio[ciccio.Count - 1].Y;
                ciccio.Add(new Point(xserp, yserp));//aggiunga 3# tassello
                xserp = ciccio[0].X; yserp = ciccio[0].Y;
                yserp -= 3;
                ciccio.Add(new Point(xserp, yserp));
                ciccio.RemoveAt(ciccio.Count - 1);//spostamento
                aggiungi();
                disegna();
               
            }
            if (dx == true)
            {
                xserp = ciccio[ciccio.Count - 1].X; yserp = ciccio[ciccio.Count - 1].Y;
                ciccio.Add(new Point(xserp, yserp));//aggiunga 1# tassello
                xserp = ciccio[0].X; yserp = ciccio[0].Y;
                xserp += 3;
                ciccio.Add(new Point(xserp, yserp));
                ciccio.RemoveAt(ciccio.Count - 1);//spostamento
                aggiungi();
                disegna();

                xserp = ciccio[ciccio.Count - 1].X; yserp = ciccio[ciccio.Count - 1].Y;
                ciccio.Add(new Point(xserp, yserp));//aggiunga 1# tassello
                xserp = ciccio[0].X; yserp = ciccio[0].Y;
                xserp += 3;
                ciccio.Add(new Point(xserp, yserp));
                ciccio.RemoveAt(ciccio.Count - 1);//spostamento
                aggiungi();
                disegna();

                xserp = ciccio[ciccio.Count - 1].X; yserp = ciccio[ciccio.Count - 1].Y;
                ciccio.Add(new Point(xserp, yserp));//aggiunga 1# tassello
                xserp = ciccio[0].X; yserp = ciccio[0].Y;
                xserp += 3;
                ciccio.Add(new Point(xserp, yserp));
                ciccio.RemoveAt(ciccio.Count - 1);//spostamento
                aggiungi();
                disegna();
            }
            if (sx == true)
            {
                xserp = ciccio[ciccio.Count - 1].X; yserp = ciccio[ciccio.Count - 1].Y;
                ciccio.Add(new Point(xserp, yserp));//aggiunga 1# tassello
                xserp = ciccio[0].X; yserp = ciccio[0].Y;
                xserp -= 3;
                ciccio.Add(new Point(xserp, yserp));
                ciccio.RemoveAt(ciccio.Count - 1);//spostamento
                aggiungi();
                disegna();

                xserp = ciccio[ciccio.Count - 1].X; yserp = ciccio[ciccio.Count - 1].Y;
                ciccio.Add(new Point(xserp, yserp));//aggiunga 1# tassello
                xserp = ciccio[0].X; yserp = ciccio[0].Y;
                xserp -= 3;
                ciccio.Add(new Point(xserp, yserp));
                ciccio.RemoveAt(ciccio.Count - 1);//spostamento
                aggiungi();
                disegna();

                xserp = ciccio[ciccio.Count - 1].X; yserp = ciccio[ciccio.Count - 1].Y;
                ciccio.Add(new Point(xserp, yserp));//aggiunga 1# tassello
                xserp = ciccio[0].X; yserp = ciccio[0].Y;
                xserp -= 3;
                ciccio.Add(new Point(xserp, yserp));
                ciccio.RemoveAt(ciccio.Count - 1);//spostamento
                aggiungi();
                disegna();
            }
        }
 
        private void melaimg_Click(object sender, EventArgs e)
        {

        }

        private void terrenopnl_Paint(object sender, PaintEventArgs e)
        {
        }
    }
}

Ecco qui il codice...