using System;

using System.Collections.Generic;

using System.Linq;

using Microsoft.Xna.Framework;

using Microsoft.Xna.Framework.Audio;

using Microsoft.Xna.Framework.Content;

using Microsoft.Xna.Framework.GamerServices;

using Microsoft.Xna.Framework.Graphics;

using Microsoft.Xna.Framework.Input;

using Microsoft.Xna.Framework.Media;





namespace Square_Catcher

{

    /// <summary>

    /// This is the main type for your game

    /// </summary>

    public class Game1 : Microsoft.Xna.Framework.Game

    {

        GraphicsDeviceManager graphics;

        SpriteBatch spriteBatch;





        Texture2D square;

        Rectangle source;

        float Time_Difficulty = 0.85f;

        float Time_Left = 0.0f;

        Color[] color = new Color[3] { Color.Red, Color.White, Color.Blue };

        Random random = new Random();

        int Playerscore = 0;





        public Game1()

        {

            graphics = new GraphicsDeviceManager(this);

            Content.RootDirectory = "Content";

        }





        /// <summary>

        /// Allows the game to perform any initialization it needs to before starting to run.

        /// This is where it can query for any required services and load any non-graphic

        /// related content.  Calling base.Initialize will enumerate through any components

        /// and initialize them as well.

        /// </summary>

        protected override void Initialize()

        {

            // TODO: Add your initialization logic here

            this.Window.Title = "Square Catcher - Score: " + Playerscore;

            this.IsMouseVisible = true;

            base.Initialize();

        }





        /// <summary>

        /// LoadContent will be called once per game and is the place to load

        /// all of your content.

        /// </summary>

        protected override void LoadContent()

        {

            // Create a new SpriteBatch, which can be used to draw textures.

            spriteBatch = new SpriteBatch(GraphicsDevice);

            square = Content.Load<Texture2D>(@"SQUARE");

            // TODO: use this.Content to load your game content here

        }





        /// <summary>

        /// UnloadContent will be called once per game and is the place to unload

        /// all content.

        /// </summary>

        protected override void UnloadContent()

        {

            // TODO: Unload any non ContentManager content here

        }





        /// <summary>

        /// Allows the game to run logic such as updating the world,

        /// checking for collisions, gathering input, and playing audio.

        /// </summary>

        /// <param name="gameTime">Provides a snapshot of timing values.</param>

        protected override void Update(GameTime gameTime)

        {

            // Allows the game to exit

            if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)

                this.Exit();





            if (Time_Left == 0.0f)

            {

                source = new Rectangle(random.Next(0, this.Window.ClientBounds.Width - 25), random.Next(0, this.Window.ClientBounds.Height - 25), 25, 25);

                Time_Left = Time_Difficulty;

            }





            MouseState mouse = Mouse.GetState();

            if (mouse.LeftButton == ButtonState.Pressed && source.Contains(mouse.X, mouse.Y))

            {

                Playerscore++;

                Time_Left = 0.0f;

                if (Time_Difficulty > 0.5f)

                {

                    Time_Difficulty -= 0.01f;

                }

            }

            Time_Left = MathHelper.Max(0, Time_Left - (float)gameTime.ElapsedGameTime.TotalSeconds);

            this.Window.Title = "Square Catcher - Score: " + Playerscore.ToString();

            // TODO: Add your update logic here





            base.Update(gameTime);

        }





        /// <summary>

        /// This is called when the game should draw itself.

        /// </summary>

        /// <param name="gameTime">Provides a snapshot of timing values.</param>

        protected override void Draw(GameTime gameTime)

        {

            GraphicsDevice.Clear(Color.Black);





            spriteBatch.Begin();

            spriteBatch.Draw(square, source, color[Playerscore % 3]);

            spriteBatch.End();





            base.Draw(gameTime);

        }

    }

}

• A save file of a transparent square, 64x64 named "SQUARE". The extension can be .bmp, jpg, png.