RandomStringInvader.cs

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Windows.Forms;

public delegate void OnStringGet(string s);
public class RandomStringInvader : Control
{
    private bool _PauseOnMouseExit = false;

    public bool PauseOnMouseExit
    {
        get
        {
            return _PauseOnMouseExit;
        }
        set
        {
            _PauseOnMouseExit = value;
            if(_PauseOnMouseExit)
            {
                if (boardX == int.MinValue)
                    Stop();
            }
            else
            {
                Start();
            }
        }
    }

    Ship[] shooters;
    Timer drawTimer;
    
    List<Collectable> FallingCollectables = new List<Collectable>();
    Random r = new Random();

    int boardX = 0;
    int boardY = 0;
    int boardWidth = 0;
    int boardHeight = 6;

    bool Stopped = false;

    public event OnStringGet OnStringGet;

    public string CharMap { get; set; }
    struct Ship
    {
        public bool reverse;
        public int X;
        public Size Size;
        public void Draw(Graphics g)
        {
            g.FillRectangle(Brushes.White, new Rectangle(new Point(X, 0), Size));
            g.FillPolygon(Brushes.White, new Point[] { new Point(X, Size.Height / 2), new Point(X + Size.Width, Size.Height / 2), new Point(X + (Size.Width / 2), Size.Height + 3) });
        }
    }

    struct Collectable
    {
        public string Letter;
        public int X;
        public int Y;
    }

    public RandomStringInvader()
    {
        CharMap = "1234567890-=qwertyuiopasdfghjklzxcvbnm,./;'[]";
        BackColor = Color.Black;
        MinimumSize = new Size(100, 100);
        drawTimer = new Timer();
        drawTimer.Interval = 50;
        drawTimer.Tick += DrawTimer_Tick;
        drawTimer.Start();
        Setup();
    }

    private void DrawTimer_Tick(object sender, EventArgs e)
    {
        for (int i = 0; i < shooters.Length; i++)
        {
            Ship shooter = shooters[i];
            int newX = shooter.X;

            if (shooter.reverse)
            {
                newX -= this.Width / 10;
                if ((newX - (shooter.Size.Width / 2)) < 0)
                {
                    newX = newX - (shooter.Size.Width / 2);
                    shooter.reverse = false;
                }
            }
            else
            {
                newX += this.Width / 10;
                if (newX > this.Width - shooter.Size.Width)
                {
                    newX = this.Width - shooter.Size.Width;
                    shooter.reverse = true;
                }
            }

            shooter.X = newX;
            shooters[i] = shooter;

            var newc = new Collectable();
            newc.Letter = CharMap[r.Next(CharMap.Length)].ToString();
            newc.X = shooter.X + (shooter.Size.Width / 2);
            newc.Y = shooter.Size.Height + 3;
            FallingCollectables.Add(newc);
        }

       

        for (int i = 0; i < FallingCollectables.Count; i++)
        {
            Collectable c = FallingCollectables[i];
            c.Y += 10;
            if (c.Y > this.Height + 10)
                FallingCollectables.RemoveAt(i);
            else
                FallingCollectables[i] = c;
        }

        Invalidate();
    }

    private void Setup()
    {
        shooters = new Ship[]
        {
            new Ship()
            {
                Size = new Size(this.Width / 10, this.Height / 10),
                reverse = false
            },
            new Ship()
            {
                Size = new Size(this.Width / 10, this.Height / 10),
                reverse = true,
                X = this.Width
            },
            new Ship()
            {
                Size = new Size(this.Width / 10, this.Height / 10),
                reverse = false,
                X = this.Width / 2
            }
        };

        boardX = int.MinValue;
        boardY = this.Height - (this.Height / 5);
        boardWidth = this.Width / 10;
    }

    protected override void OnPaint(PaintEventArgs e)
    {
        var g = e.Graphics;

        if(boardX != int.MinValue)
            g.FillRectangle(Brushes.Green, new Rectangle(boardX, boardY, boardWidth, boardHeight));

       

        foreach (Ship s in shooters)
            s.Draw(g);


        for (int i = 0; i < FallingCollectables.Count; i++)
        {
            Collectable c = FallingCollectables[i];
            if ((c.X > boardX && c.X < boardX + boardWidth) && (c.Y > boardY))
            {
                FallingCollectables.RemoveAt(i);
                var callback = OnStringGet;
                if (callback != null)
                    callback(c.Letter);
            }
            else
            {
                g.DrawString(c.Letter, this.Font, Brushes.Red, new Point(c.X, c.Y));
            }
        }

        base.OnPaint(e);
    }
    protected override void OnSizeChanged(EventArgs e)
    {
        base.OnSizeChanged(e);
        Setup();
    }

    protected override void OnMouseMove(MouseEventArgs e)
    {
        base.OnMouseMove(e);
        if(!Stopped)
            boardX = e.X;
    }

    protected override void OnMouseLeave(EventArgs e)
    {
        boardX = int.MinValue;
        if (PauseOnMouseExit)
            Stop();
        base.OnMouseLeave(e);
    }

    protected override void OnMouseEnter(EventArgs e)
    {
        if (PauseOnMouseExit)
            Start();
        base.OnMouseEnter(e);
    }

    public void Stop()
    {
        Stopped = true;
        boardX = int.MinValue;
        drawTimer.Stop();
    }


    public void Start()
    {
        Stopped = false;
        drawTimer.Start();
    }

    public void ClearCharacters()
    {
        FallingCollectables.Clear();
        Invalidate();
    }


}