Added texture cache and sprite origins.

AlientAttack.MonoGame/Things/Asteroids/Asteroid.cs

@@ -0,0 +1,48 @@
+using Microsoft.Xna.Framework;
+using Microsoft.Xna.Framework.Graphics;
+
+namespace AlienAttack.MonoGame.Things.Asteroids;
+
+public class Asteroid : MoveableSprite
+{
+    public const int Width = 39;
+    public const int Height = 37;
+
+    protected float Rotation = 0;
+
+    public Asteroid(int x, int y) : base(x, y)
+    {
+        Origin = new(Width / 2, Height / 2);
+        BoundBox = new(0, 0, Width, Height);
+        YVelocity = 1;
+        XVelocity = 0;
+    }
+
+    public override void Draw(SpriteDrawArgs args)
+    {
+        Texture2D texture = args.Content.Load<Texture2D>("Sprites/Asteroid 01");
+        args.SpriteBatch.Draw(texture, Position, null, DrawColor, Rotation, Origin, 1f, SpriteEffects.None, 1);
+
+        base.Draw(args);
+    }
+
+    public override sealed void Update(SpriteUpdateContext context)
+    {
+        base.Update(context);
+
+        CollisionBox = new Rectangle((int)XPosition + BoundBox.X - (int)Origin.X, (int)YPosition + BoundBox.Y - (int)Origin.Y, BoundBox.Width, BoundBox.Height);
+
+        if (YPosition - Origin.Y > context.ViewTransform.ScreenHeight)
+        {
+            IsDead = true;
+            return;
+        }
+
+        Rotation += 0.01f;
+
+        if (Rotation > 360f)
+        {
+            Rotation = 0;
+        }
+    }
+}