Added Golden Axe Warrior. Added Debugger.

Core/Io/SmsIoBus.cs

@@ -0,0 +1,62 @@
+using Core.Interfaces;
+
+namespace Core.Io
+{
+    public class SmsIoBus : IIoBus
+    {
+        // We will wire these up in the next phases!
+        // public Vdp VideoProcessor { get; set; }
+        // public Psg AudioProcessor { get; set; }
+
+        // Joypad State (0xFF means no buttons pressed - the SMS uses Active-Low logic!)
+        public byte Joypad1State { get; set; } = 0xFF;
+        public byte Joypad2State { get; set; } = 0xFF;
+
+        public byte ReadPort(ushort port)
+        {
+            // The Z80 can output 16-bit port addresses, but the Master System 
+            // hardware only physically wires up the bottom 8 bits.
+            byte lowerPort = (byte)(port & 0xFF);
+
+            if (lowerPort >= 0x80 && lowerPort <= 0xBF)
+            {
+                // VDP Read (Usually 0xBE for VRAM Data, 0xBF for Status Flags)
+                // return VideoProcessor.ReadPort(lowerPort);
+                return 0x00;
+            }
+            if (lowerPort == 0xDC)
+            {
+                // Port 0xDC: Player 1 (Up, Down, Left, Right, 1, 2) + Player 2 (Up, Down)
+                return Joypad1State;
+            }
+            if (lowerPort == 0xDD)
+            {
+                // Port 0xDD: Player 2 (Left, Right, 1, 2) + Reset Button
+                return Joypad2State;
+            }
+
+            return 0xFF; // Floating bus
+        }
+
+        public void WritePort(ushort port, byte value)
+        {
+            byte lowerPort = (byte)(port & 0xFF);
+
+            if (lowerPort >= 0x40 && lowerPort <= 0x7F)
+            {
+                // PSG Audio Write (Usually written exactly to 0x7F)
+                // AudioProcessor.WriteData(value);
+            }
+            else if (lowerPort >= 0x80 && lowerPort <= 0xBF)
+            {
+                // VDP Write (Usually 0xBE for VRAM Data, 0xBF for Control Registers)
+                // VideoProcessor.WritePort(lowerPort, value);
+            }
+            else if (lowerPort <= 0x3F)
+            {
+                // Port 0x3E is used by the BIOS to enable/disable the cartridge slot
+                // We can usually ignore this if we are just directly booting game ROMs!
+            }
+        }
+    }
+}