Flyatron player animation.

/*
 * Date: 21/07/2012
 * Author: Mark Grealish
 *
 * A very simple sprite animation guide. I chose to preclude the use of a timer and instead demonstrate
 * how different frames are loaded based on given criteria. This illustration has six frames that relate
 * to the mouse's position within the game window.
 *
 * Questions? Feedback? Email mark@bhalash.com
 *
 * Enjoy and share!
 */

using System;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;
using Microsoft.Xna.Framework.Media;
using System.Collections.Generic;
using System.Diagnostics;

namespace Animmmmmation
{
    public class Game1 : Microsoft.Xna.Framework.Game
    {
        bool debug = true;

        GraphicsDeviceManager graphics;
        SpriteBatch spriteBatch;

        int gameWidth = 1024;
        int gameHeight = 600;
        bool fullScreen = false;
        bool showMouse = true;

        SpriteFont font;

        Rectangle bodyRectangle, headRectangle, gunRectangle, flamesRectangle;
        Texture2D headTexture, bodyTexture, gunTexture, flameTexture;
        Vector2 head, headOffset, body, gun, gunOffset, flames;
        float headRotation, bodyRotation, gunRotation;
        int gunWidth, gunHeight, headWidth, headHeight;
        int bodyWidth, bodyHeight, flamesWidth, flamesHeight;
        Stopwatch flamesTimer;

        MouseState currentMouseState, previousMouseState;
        KeyboardState currentKeyboardState, previousKeyboardState;

        float velocity = 15f;

        public Game1()
        {
            graphics = new GraphicsDeviceManager(this);
            graphics.PreferredBackBufferWidth = gameWidth;
            graphics.PreferredBackBufferHeight = gameHeight;
            this.graphics.IsFullScreen = fullScreen;
            this.IsMouseVisible = showMouse;

            Content.RootDirectory = "Content";
        }

        protected override void Initialize()
        {
            flamesWidth  = 23;
            flamesHeight = 46;

            gunWidth  = 35;
            gunHeight = 18;

            bodyWidth  = 35;
            bodyHeight = 72;

            headWidth  = 35;
            headHeight = 35;

            headRectangle   = new Rectangle(0, 0, headWidth, headHeight);
            bodyRectangle   = new Rectangle(0, 0, bodyWidth, bodyHeight);
            gunRectangle    = new Rectangle(0, 0, gunWidth, gunHeight);
            flamesRectangle = new Rectangle(0, 0, flamesWidth, flamesHeight);

            body = new Vector2(100,100);
            head = new Vector2(117.5F,117.5F);
            gun = new Vector2(117.5F, 145);
            flames = new Vector2(106, 154);

            // These are the centre of the respective texture frames, used to correctly rotate them.
            headOffset = new Vector2(17.5F, 17.5F);
            gunOffset = new Vector2(17.5F, 9F);

            bodyRotation = 0;
            headRotation = 0;
            gunRotation  = 0;

            flamesTimer = new Stopwatch();
            flamesTimer.Start();

            base.Initialize();
        }

        protected override void LoadContent()
        {
            spriteBatch = new SpriteBatch(GraphicsDevice);
            font = Content.Load<SpriteFont>("font1");

            headTexture = Content.Load<Texture2D>("head");
            bodyTexture = Content.Load<Texture2D>("body");
            gunTexture = Content.Load<Texture2D>("gun");
            flameTexture = Content.Load<Texture2D>("flames");
        }

        protected override void UnloadContent()
        {
        }

        protected override void Update(GameTime gameTime)
        {
            currentKeyboardState = Keyboard.GetState();
            currentMouseState = Mouse.GetState();

            UpdateHead(currentMouseState);
            UpdateBody(currentMouseState);
            UpdateGun(currentMouseState);
            UpdateFlames();

            if (Keyboard.GetState().IsKeyDown(Keys.Escape))
                this.Exit();
            if (Keyboard.GetState().IsKeyDown(Keys.Space))
                this.Exit();

            Move(currentKeyboardState);

            previousMouseState = currentMouseState;
            previousKeyboardState = currentKeyboardState;

            base.Update(gameTime);
        }

        protected override void Draw(GameTime gameTime)
        {
            GraphicsDevice.Clear(Color.CornflowerBlue);

            spriteBatch.Begin();

            if (debug)
                Debug(font, spriteBatch);

            // Player Flames.
            spriteBatch.Draw(
                flameTexture,
                flames,
                flamesRectangle,
                Color.White,
                0,
                new Vector2(0, 0),
                1,
                SpriteEffects.None,
                0
            );

            // Player body.
            spriteBatch.Draw(
                bodyTexture,
                body,
                bodyRectangle,
                Color.White,
                bodyRotation,
                new Vector2(0, 0),
                1,
                SpriteEffects.None,
                0
            );

            // Player head.
            spriteBatch.Draw(
                headTexture,
                head,
                headRectangle,
                Color.White,
                headRotation,
                headOffset,
                1,
                SpriteEffects.None,
                0
            );

            // Player weapon.
            spriteBatch.Draw(
                gunTexture,
                gun,
                gunRectangle,
                Color.White,
                gunRotation,
                gunOffset,
                1,
                SpriteEffects.None,
                0
            );

            spriteBatch.End();

            base.Draw(gameTime);
        }

        private void Debug(SpriteFont font, SpriteBatch spriteBatch)
        {
            int x = 30;
            int y = 30;

            List<string> debugMsg = new List<string>()
            {
                "Head:",
                "X: " + head.X,
                "Y: " + head.Y,
                "Rotation: " + headRotation,
                "",
                "Gun:",
                "X: " + gun.X,
                "Y: " + gun.Y,
                "Rotation: " + gunRotation,
                "",
                "Body:",
                "X: " + body.X,
                "Y: " + body.Y,
                "",
                "Flames:",
                "X: " + flames.X,
                "Y: " + flames.Y,
                "Timer: " + flamesTimer.ElapsedMilliseconds
            };

            for (int i = 0; i < debugMsg.Count; i++)
            {
                spriteBatch.DrawString(font, debugMsg[i], new Vector2(x, y), Color.Black);
                y += 20;
            }

        }

        private void UpdateHead(MouseState mouse)
        {
            Vector2 mouseLoc = new Vector2(mouse.X, mouse.Y);

            Vector2 leftFacing = new Vector2(head.X - mouse.X, head.Y - mouse.Y);
            Vector2 rightFacing = new Vector2(mouse.X - head.X, mouse.Y - head.Y);

            float leftAngle = (float)(Math.Atan2(leftFacing.Y, leftFacing.X));
            float rightAngle = (float)(Math.Atan2(rightFacing.Y, rightFacing.X));

            if (mouse.X < head.X)
            {
                headRotation = leftAngle;
                headRectangle = new Rectangle(44, 0, headWidth, headHeight);
            }
            if (mouse.X > head.X)
            {
                headRotation = rightAngle;
                headRectangle = new Rectangle(0, 0, headWidth, headHeight);
            }
        }

        private void UpdateGun(MouseState mouse)
        {
            Vector2 mouseLoc = new Vector2(mouse.X, mouse.Y);

            Vector2 leftFacing = new Vector2(gun.X - mouse.X, gun.Y - mouse.Y);
            Vector2 rightFacing = new Vector2(mouse.X - gun.X, mouse.Y - gun.Y);

            float leftAngle = (float)(Math.Atan2(leftFacing.Y, leftFacing.X));
            float rightAngle = (float)(Math.Atan2(rightFacing.Y, rightFacing.X));

            if (mouse.X < gun.X)
            {
                gunRotation = leftAngle;
                gunRectangle = new Rectangle(39, 0, gunWidth, gunHeight);
            }
            if (mouse.X > gun.X)
            {
                gunRotation = rightAngle;
                gunRectangle = new Rectangle(0, 0, gunWidth, gunHeight);
            }
        }

        private void UpdateBody(MouseState mouse)
        {

            if (mouse.X < body.X)
            {
                bodyRectangle = new Rectangle(40, 0, bodyWidth, bodyHeight);
            }
            if (mouse.X > body.X)
            {
                bodyRectangle = new Rectangle(0, 0, bodyWidth, bodyHeight);
            }
        }

        private void UpdateFlames()
        {
            if ((flamesTimer.ElapsedMilliseconds >= 0) && (flamesTimer.ElapsedMilliseconds < 300))
                flamesRectangle = new Rectangle(52, 0, flamesWidth, flamesHeight);
            if ((flamesTimer.ElapsedMilliseconds >= 300) && (flamesTimer.ElapsedMilliseconds < 600))
                flamesRectangle = new Rectangle(25, 0, flamesWidth, flamesHeight);
            if ((flamesTimer.ElapsedMilliseconds >= 600) && (flamesTimer.ElapsedMilliseconds < 900))
                flamesRectangle = new Rectangle(0, 0, flamesWidth, flamesHeight);

            if (flamesTimer.ElapsedMilliseconds > 900)
                flamesTimer.Restart();
        }

        private void Move(KeyboardState keyboard)
        {
            if (Keyboard.GetState().IsKeyDown(Keys.W))
            {
                if (body.Y > 0)
                {
                    gun.Y  -= velocity;
                    body.Y -= velocity;
                    head.Y -= velocity;
                    flames.Y -= velocity;
                }
            }
            if (Keyboard.GetState().IsKeyDown(Keys.S))
            {
                if (body.Y + bodyRectangle.Height < gameHeight)
                {
                    gun.Y  += velocity;
                    body.Y += velocity;
                    head.Y += velocity;
                    flames.Y += velocity;
                }
            }
            if (Keyboard.GetState().IsKeyDown(Keys.A))
            {
                if (body.X > 0)
                {
                    gun.X  -= velocity;
                    body.X -= velocity;
                    head.X -= velocity;
                    flames.X -= velocity;
                }
            }
            if (Keyboard.GetState().IsKeyDown(Keys.D))
            {
                if (body.X + bodyRectangle.Width < gameWidth)
                {
                    gun.X  += velocity;
                    body.X += velocity;
                    head.X += velocity;
                    flames.X += velocity;
                }
            }

        }
    }
}