Starfield.cs

using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using Nez;
using Nez.Sprites;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

/// <summary>
/// Generic parallax starfield effect
/// </summary>
namespace ThreeThirty.Scenes.Effects
{
    public class Starfield : Component, IUpdatable
    {
        TiledSprite background;
        float scrollAmount;

        public Starfield(float scroll)
        {
            scrollAmount = scroll;
        }

        public override void onAddedToEntity()
        {
            base.onAddedToEntity();

            // load our sprite
            background = new TiledSprite(Core.content.Load<Texture2D>("backgrounds/starfield"));
            entity.addComponent(background);
            entity.transform.localScale = new Vector2(scrollAmount, scrollAmount);

            // tile and position it correctly
            Core.emitter.addObserver(CoreEvents.GraphicsDeviceReset, onGraphicsDeviceReset);
            onGraphicsDeviceReset();
        }

        /// <summary>
        /// Reset dimensions when screen changes size
        /// </summary>
        private void onGraphicsDeviceReset()
        {
            background.width = Core.graphicsDevice.Viewport.Width;
            background.height = Core.graphicsDevice.Viewport.Height;
            background.origin = new Vector2(background.width / 2, background.height / 2);
        }

        /// <summary>
        /// Parallax effect
        /// </summary>
        public void update()
        {
            background.scrollX = (int)(entity.transform.position.X * scrollAmount);
            background.scrollY = (int)(entity.transform.position.Y * scrollAmount);
        }
    }
}