Add project files.

AlientAttack.MonoGame/Things/Weapons/Weapon.cs

@@ -0,0 +1,26 @@
+namespace AlienAttack.MonoGame.Things.Weapons;
+
+public abstract class Weapon : IWeapon
+{
+    public abstract int FireThreshold { get; }
+    public int CurrentFireThreshold { get; private set; }
+
+    public void UpdateFireThreshold()
+    {
+        if (CurrentFireThreshold > 0)
+            CurrentFireThreshold--;
+    }
+
+    public bool TryFire(Sprite owner, SpriteUpdateContext context)
+    {
+        if (CurrentFireThreshold > 0)
+            return false;
+
+        Fire(owner, context);
+        CurrentFireThreshold = FireThreshold;
+
+        return true;
+    }
+
+    public abstract void Fire(Sprite owner, SpriteUpdateContext context);
+}