Add initial game systems and input handling for player interactions

Assets/Scripts/Core/Systems/ScoreSystem.cs

@@ -0,0 +1,26 @@
+using System;
+
+namespace Core.Systems
+{
+    public class ScoreSystem : IDisposable
+    {
+        private int _currentScore;
+
+        public ScoreSystem()
+        {
+            _currentScore = 0;
+            GameEvents.PresentCaught += OnPresentCaught;
+        }
+
+        private void OnPresentCaught(int value)
+        {
+            _currentScore += value;
+            GameEvents.ReportScoreUpdated(_currentScore);
+        }
+
+        public void Dispose()
+        {
+            GameEvents.PresentCaught -= OnPresentCaught;
+        }
+    }
+}