Add initial game systems and input handling for player interactions

Assets/Scripts/Core/Systems/TimeAttackSystem.cs

@@ -0,0 +1,51 @@
+using System;
+
+namespace Core.Systems
+{
+    public class TimeAttackSystem : IDisposable
+    {
+        private float _timeRemaining;
+        private readonly float _penaltyPerDrop;
+        
+        public TimeAttackSystem(float initialTime, float penaltyPerDrop = 5f)
+        {
+            _timeRemaining = initialTime;
+            _penaltyPerDrop = penaltyPerDrop;
+            
+            GameEvents.ReportTimeUpdated(_timeRemaining);
+            
+            GameEvents.PresentDropped += OnPresentDropped;
+        }
+
+        public void Tick(float deltaTime)
+        {
+            if (_timeRemaining <= 0) return;
+            
+            _timeRemaining -= deltaTime;
+
+            if (_timeRemaining <= 0)
+            {
+                _timeRemaining = 0;
+                GameEvents.ReportTimeUpdated(0f);
+                GameEvents.ReportGameOver();
+            }
+            else
+            {
+                GameEvents.ReportTimeUpdated(_timeRemaining);
+            }
+        }
+
+        private void OnPresentDropped()
+        {
+            if (_timeRemaining > 0)
+            {
+                _timeRemaining -= _penaltyPerDrop;
+            }
+        }
+
+        public void Dispose()
+        {
+            GameEvents.PresentDropped -= OnPresentDropped;
+        }
+    }
+}