Implement basic structure for combat system and refactor code

Assets/Scripts/Meta/EntropyWallet.cs

@@ -0,0 +1,26 @@
+namespace KernelPanic.Meta
+{
+    /// <summary>
+    /// Tracks the player's persistent entropy currency balance.
+    /// </summary>
+    public sealed class EntropyWallet
+    {
+        public int Balance { get; private set; }
+
+        public void Add(int amount)
+        {
+            Balance += amount;
+        }
+
+        public bool Spend(int amount)
+        {
+            if (Balance < amount)
+            {
+                return false;
+            }
+
+            Balance -= amount;
+            return true;
+        }
+    }
+}