Как правильно задавать отражение мяча в противоположную сторону

#region Support Directives
using System;
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;
#endregion
 
#region Ball
namespace P
{
    public class ball
    {
        private Texture2D ball_texture { get; set; }
        public Rectangle ball_rectangle { get; set; }
        private Vector2 ball_position { get; set; }
        private Vector2 ball_origin { get; set; }
        private float ball_rotation { get; set; }
 
        private float ball_scale { get; set; }
        private int ball_speed_x { get; set; }
        private int ball_speed_y { get; set; }
 
        Game1 game;
 
        public int x, y;
 
        public ball(Texture2D texture, Vector2 position, float rotation, float scale, int speed_x, int speed_y, Game1 game)
        {
            ball_texture = texture;
            ball_position = position;
            ball_rotation = rotation;
            ball_scale = scale;
            ball_speed_x = speed_x;
            ball_speed_y = speed_y;
 
            this.game = game;
        }
 
        public void Draw(SpriteBatch spriteBatch)
        {
            spriteBatch.Draw(ball_texture, ball_position, null, Color.White, ball_rotation, ball_origin, ball_scale, SpriteEffects.None, 0);
        }
 
        public void Update(GameTime gameTime)
        {
            ball_rectangle = new Rectangle((int)ball_position.X, (int)ball_position.Y, ball_texture.Width, ball_texture.Height);
            ball_origin = new Vector2(ball_rectangle.Width / 2, ball_rectangle.Height / 2);
 
            x += ball_speed_x * gameTime.ElapsedGameTime.Milliseconds / 10;
            y += ball_speed_y * gameTime.ElapsedGameTime.Milliseconds / 10;
 
            ball_position = new Vector2(x, y);
 
            if (x - 10 < 0)
            {
                ball_speed_x = Math.Abs(ball_speed_x); ball_rotation = 0;
            }
            else if (y - 10 < 0)
            {
                ball_speed_y = Math.Abs(ball_speed_y); ball_rotation = 0;
            }
            else if (x + 10 > game.Window.ClientBounds.Width)
            {
                ball_speed_x = -Math.Abs(ball_speed_x); ball_rotation = 0;
            }
            else if (y + 10 > game.Window.ClientBounds.Height)
            {
                ball_speed_y = -Math.Abs(ball_speed_y); ball_rotation = 0;
            }
            else ball_rotation += 0.1f;
        }
    }
}
#endregion

            graphics = new GraphicsDeviceManager(this);
            widthscreen = graphics.PreferredBackBufferWidth - 50;   //x
            heightscreen = graphics.PreferredBackBufferHeight - 50; //y