Added more sound effects. Added initial weapon muzzle fire logic.

AlientAttack.MonoGame/Things/Muzzles/MuzzleMath.cs

@@ -0,0 +1,20 @@
+using Microsoft.Xna.Framework;
+
+namespace AlienAttack.MonoGame.Things.Muzzles;
+
+public static class MuzzleMath
+{
+    public static Vector2 GetMuzzleWorld(Sprite owner, Vector2 muzzleLocalPx, float ownerScale = 1f)
+    {
+        // Assumes owner.Position is the top-left of the sprite
+        return owner.Position + muzzleLocalPx * ownerScale;
+    }
+
+    public static Vector2 CenterBulletOn(Vector2 muzzleWorld, int bulletW, int bulletH)
+    {
+        return new Vector2(
+            muzzleWorld.X - bulletW / 2f,
+            muzzleWorld.Y - bulletH / 2f
+        );
+    }
+}