Added some GG games

Core/Memory/SmsMemoryBus.cs

@@ -6,6 +6,7 @@ namespace Core.Memory
 {
     public class SmsMemoryBus : IMemory
     {
+        private bool _isCodemastersMapper = false; //Codemasters used their own memory mapper
         // SMS has 8KB of internal Work RAM
         private readonly byte[] _workRam = new byte[0x2000];
 
@@ -49,6 +50,10 @@ namespace Core.Memory
 
             if (address < 0x4000)
             {
+                if (!_isCodemastersMapper && address < 0x0400)
+                {
+                    return _cartridgeRom[address];
+                }
                 if (address < 0x0400)
                 {
                     return _cartridgeRom[address];
@@ -76,6 +81,18 @@ namespace Core.Memory
 
         public void Write(ushort address, byte value)
         {
+            // Codemasters games bank-switch by writing directly to ROM!
+            if (address == 0x0000 || address == 0x4000 || address == 0x8000)
+            {
+                _isCodemastersMapper = true;
+                int cTotalBanks = _cartridgeRom.Length / 0x4000;
+                if (cTotalBanks == 0) cTotalBanks = 1;
+
+                if (address == 0x0000) _romBank0 = value % cTotalBanks;
+                else if (address == 0x4000) _romBank1 = value % cTotalBanks;
+                else if (address == 0x8000) _romBank2 = value % cTotalBanks;
+                return;
+            }
             if (address < 0x8000) return; // Cannot write to physical ROM
 
             if (address < 0xC000)
@@ -266,6 +283,7 @@ namespace Core.Memory
         {
             Array.Clear(_workRam, 0, _workRam.Length);
             _mapperControl = 0;
+            _isCodemastersMapper = false;
         }
     }
 }