diff --git a/MCEmuCore.GBMonolith/Cpu.cs b/MCEmuCore.GBMonolith/Cpu.cs
index 4433798..c37d83e 100644
--- a/MCEmuCore.GBMonolith/Cpu.cs
+++ b/MCEmuCore.GBMonolith/Cpu.cs
@@ -27,7 +27,8 @@ namespace MCEmuCore.GBMonolith
             
             OpCodeTable = new Dictionary<byte, Func<OpCode, bool>>()
             {
-                {0x00, (op) => {
+                #region OpCodes 0x00-0x0F
+                {0x00, (op) =>{
                     registers.PC += 1;
                     return true;
                 } },
@@ -65,11 +66,188 @@ namespace MCEmuCore.GBMonolith
 
                     registers.Flags.Subtract = false;
                     registers.Flags.Zero = reg == 0;
+                    // This logic only works for the increment operation
                     registers.Flags.HalfCarry = reg == 16;
 
                     registers.PC += 1;
                     return true;
+                } },
+                {0x05, (op) =>
+                {
+                    // DEC B
+                    byte reg = (byte)((uint)registers.B - 1);
+                    registers.B = reg;
+
+                    registers.Flags.Subtract = true;
+                    registers.Flags.Zero = reg == 0;
+                    // This logic only works for the decrement operation
+                    registers.Flags.HalfCarry = reg == 15;
+
+                    registers.PC += 1;
+                    return true;
+                } },
+                {0x06, (op) =>
+                {
+                    // LD B,d8
+                    if (op.Arg1.HasValue)
+                    {
+                        registers.B = op.Arg1.Value;
+                        registers.PC += 2;
+                        return true;
+                    }
+                    else
+                    {
+                        throw new InvalidOperationException(op, "Missing arguments for LD B");
+                    }
+                } },
+                {0x07, (op) =>
+                {
+                    // RLCA
+                    registers.Flags.Zero = false;
+                    registers.Flags.Subtract = false;
+                    registers.Flags.HalfCarry = false;
+                    registers.Flags.Carry = (registers.A & 0b1000_0000) != 0;
+                    
+                    registers.A = (byte)((registers.A << 1) + (registers.A >> 7));
+                    registers.PC += 1;
+                    return true;
+                } },
+                {0x08, (op) =>
+                {
+                    // LD (a16), SP
+                    // Load SP into address
+                    throw new NotImplementedException("LD (a16), SP");
+                } },
+                {0x09, (op) =>
+                {
+                    // ADD HL, BC
+                    registers.Flags.Subtract = false;
+                    registers.Flags.HalfCarry = (((registers.HL & 0x0FFF) + (registers.BC & 0x0FFF) & 0x1000) == 0x1000);
+                    registers.Flags.Carry = (((registers.HL + registers.BC) & 0x10000) == 0x10000);
+
+                    registers.HL += registers.BC;
+                    registers.PC += 1;
+
+                    return true;
+                } },
+                {0x0A, (op) =>
+                {
+                    // LD A, (BC)
+                    // Load byte at address stored in BC into A
+                    throw new NotImplementedException("LD A, (BC)");
+                } },
+                {0x0B, (op) =>
+                {
+                    // DEC BC
+                    registers.BC -= 1;
+                    registers.PC += 1;
+                    return true;
+                } },
+                {0x0C, (op) =>
+                {
+                    // INC C
+                    byte reg = (byte)(registers.C + 1);
+                    registers.C = reg;
+
+                    registers.Flags.Subtract = false;
+                    registers.Flags.Zero = reg == 0;
+                    // This logic only works for the increment operation
+                    registers.Flags.HalfCarry = reg == 16;
+
+                    registers.PC += 1;
+                    return true;
+                } },
+                {0x0D, (op) =>
+                {
+                    // DEC C
+                    byte reg = (byte)((uint)registers.C - 1);
+                    registers.C = reg;
+
+                    registers.Flags.Subtract = true;
+                    registers.Flags.Zero = reg == 0;
+                    // This logic only works for the decrement operation
+                    registers.Flags.HalfCarry = reg == 15;
+
+                    registers.PC += 1;
+                    return true;
+                } },
+                {0x0E, (op) =>
+                {
+                    // LD C,d8
+                    if (op.Arg1.HasValue)
+                    {
+                        registers.C = op.Arg1.Value;
+                        registers.PC += 2;
+                        return true;
+                    }
+                    else
+                    {
+                        throw new InvalidOperationException(op, "Missing argument for LD B");
+                    }
+                } },
+                {0x0F, (op) =>
+                {
+                    // RRCA
+                    registers.Flags.Zero = false;
+                    registers.Flags.Subtract = false;
+                    registers.Flags.HalfCarry = false;
+                    registers.Flags.Carry = (registers.A & 0b0000_0001) != 0;
+
+                    registers.A = (byte)((registers.A >> 1) + (registers.A << 7));
+                    registers.PC += 1;
+                    return true;
+                } },
+                #endregion
+                #region OpCodes 0x10-0x1F
+                {0x10, (op) =>
+                {
+                    // STOP 0
+                    // Halts CPU & LCD until button pressed
+                    throw new NotImplementedException("STOP");
                 } }
+                #endregion
+                #region OpCodes 0x20-0x2F
+
+                #endregion
+                #region OpCodes 0x30-0x3F
+
+                #endregion
+                #region OpCodes 0x40-0x4F
+
+                #endregion
+                #region OpCodes 0x50-0x5F
+
+                #endregion
+                #region OpCodes 0x60-0x6F
+
+                #endregion
+                #region OpCodes 0x70-0x7F
+
+                #endregion
+                #region OpCodes 0x80-0x8F
+
+                #endregion
+                #region OpCodes 0x90-0x9F
+
+                #endregion
+                #region OpCodes 0xA0-0xAF
+
+                #endregion
+                #region OpCodes 0xB0-0xBF
+
+                #endregion
+                #region OpCodes 0xC0-0xCF
+
+                #endregion
+                #region OpCodes 0xD0-0xDF
+
+                #endregion
+                #region OpCodes 0xE0-0xEF
+
+                #endregion
+                #region OpCodes 0xF0-0xFF
+
+                #endregion
             };
         }
     }
diff --git a/MCEmuCore.GBMonolith/CpuRegisters.cs b/MCEmuCore.GBMonolith/CpuRegisters.cs
index 86d3aa5..31f7b89 100644
--- a/MCEmuCore.GBMonolith/CpuRegisters.cs
+++ b/MCEmuCore.GBMonolith/CpuRegisters.cs
@@ -252,7 +252,13 @@ namespace MCEmuCore.GBMonolith
 
         public class FlagRegister
         {
-            protected internal byte Value { get; set; }
+            private byte register;
+            public byte Value {
+                get => register;
+                set {
+                    register = (byte)(value & 0b1111_0000);
+                }
+            }
             #region Boolean Flag Properties
             public bool Zero
             {
diff --git a/MCEmuCore.GBMonolith/Program.cs b/MCEmuCore.GBMonolith/Program.cs
index c533403..55c5f46 100644
--- a/MCEmuCore.GBMonolith/Program.cs
+++ b/MCEmuCore.GBMonolith/Program.cs
@@ -11,7 +11,7 @@ namespace MCEmuCore.GBMonolith
 
         static void TestRegisters()
         {
-            CpuRegisters cpuRegisters = new CpuRegisters(true);
+            CpuRegisters cpuRegisters = new CpuRegisters(0);
             Console.WriteLine("Initializing registers:");
             Console.WriteLine("A:\t1\tF:\t16");
             Console.WriteLine("B:\t2\tC:\t100");