diff --git a/src/emu.cpp b/src/emu.cpp
index 922ea17..e0eff8c 100644
--- a/src/emu.cpp
+++ b/src/emu.cpp
@@ -32,6 +32,31 @@ void EmulatorState::reset() {
     draw_dirty = true;
 }
 
+// reads 0x0NNN
+uint16_t readAddress(const uint16_t opcode) {
+    return opcode & 0x0fff;
+}
+
+// reads 0x00NN
+uint8_t readNN(const uint16_t opcode) {
+    return opcode & 0x00ff;
+}
+
+// reads 0x000N
+uint8_t readN(const uint16_t opcode) {
+    return (opcode & 0x000f);
+}
+
+// reads 0x0X00
+uint8_t readX(const uint16_t opcode) {
+    return (opcode & 0x0f00) >> 8;
+}
+
+// reads 0x00Y0
+uint8_t readY(const uint16_t opcode) {
+    return (opcode & 0x00f0) >> 4;
+}
+
 typedef void (*cpu_func)(const uint16_t opcode);
 
 void null_func(const uint16_t opcode) {
@@ -91,24 +116,23 @@ void operation0(const uint16_t opcode) {
 
 // 1NNN
 void operation1(const uint16_t opcode) {
-    const uint16_t nnn = opcode & 0x0fff;
+    const auto nnn = readAddress(opcode);
 
     state.PC = nnn;
 }
 
 // 2NNN
 void operation2(const uint16_t opcode) {
-    const uint16_t nnn = opcode & 0x0fff;
+    const auto nnn = readAddress(opcode);
 
-    state.stack[state.stack_pointer] = state.PC;
-    state.stack_pointer++;
+    state.stack[state.stack_pointer++] = state.PC;
     state.PC = nnn;
 }
 
 // 3XNN
 void operation3(const uint16_t opcode) {
-    const uint8_t x = (opcode & 0x0f00) >> 8;
-    const uint8_t nn = opcode & 0x00ff;
+    const auto x = readX(opcode);
+    const auto nn = readNN(opcode);
 
     if(state.v[x] == nn)
         state.PC += 4;
@@ -118,8 +142,8 @@ void operation3(const uint16_t opcode) {
 
 // 4XNN
 void operation4(const uint16_t opcode) {
-    const uint8_t x = (opcode & 0x0f00) >> 8;
-    const uint8_t nn = opcode & 0x00ff;
+    const auto x = readX(opcode);
+    const auto nn = readNN(opcode);
     
     if(state.v[x] != nn)
         state.PC += 4;
@@ -129,28 +153,26 @@ void operation4(const uint16_t opcode) {
 
 // 6XNN
 void operation6(const uint16_t opcode) {
-    const uint8_t x = (opcode & 0x0f00) >> 8;
-    const uint8_t nn = opcode & 0x00ff;
+    const auto x = readX(opcode);
+    const auto nn = readNN(opcode);
     
     state.v[x] = nn;
-    
     state.PC += 2;
 }
 
 // &XNN
 void operation7(const uint16_t opcode) {
-    const uint8_t x = (opcode & 0x0f00) >> 8;
-    const uint8_t nn = opcode & 0x00ff;
+    const auto x = readX(opcode);
+    const auto nn = readNN(opcode);
     
     state.v[x] += nn;
-    
     state.PC += 2;
 }
 
 // 8XY0
 void op8_func0(const uint16_t opcode) {
-    const uint8_t x = (opcode & 0x0f00) >> 8;
-    const uint8_t y = (opcode & 0x00f0) >> 4;
+    const auto x = readX(opcode);
+    const auto y = readY(opcode);
     
     state.v[x] = state.v[y];
     state.PC += 2;
@@ -158,8 +180,8 @@ void op8_func0(const uint16_t opcode) {
 
 // 8XY1
 void op8_func2(const uint16_t opcode) {
-    const uint8_t x = (opcode & 0x0f00) >> 8;
-    const uint8_t y = (opcode & 0x00f0) >> 4;
+    const auto x = readX(opcode);
+    const auto y = readY(opcode);
     
     state.v[x] = state.v[x] & state.v[y];
     state.PC += 2;
@@ -167,8 +189,8 @@ void op8_func2(const uint16_t opcode) {
 
 // 8XY3
 void op8_func3(const uint16_t opcode) {
-    const uint8_t x = (opcode & 0x0f00) >> 8;
-    const uint8_t y = (opcode & 0x00f0) >> 4;
+    const auto x = readX(opcode);
+    const auto y = readY(opcode);
     
     state.v[x] = state.v[x] ^ state.v[y];
     state.PC += 2;
@@ -176,8 +198,8 @@ void op8_func3(const uint16_t opcode) {
 
 // 8XY4
 void op8_func4(const uint16_t opcode) {
-    const uint8_t x = (opcode & 0x0f00) >> 8;
-    const uint8_t y = (opcode & 0x00f0) >> 4;
+    const auto x = readX(opcode);
+    const auto y = readY(opcode);
     
     // TODO: implement tests
     if(state.v[y] < (0xFF - state.v[x]))
@@ -191,8 +213,8 @@ void op8_func4(const uint16_t opcode) {
 
 // 8XY5
 void op8_func5(const uint16_t opcode) {
-    const uint8_t x = (opcode & 0x0f00) >> 8;
-    const uint8_t y = (opcode & 0x00f0) >> 4;
+    const auto x = readX(opcode);
+    const auto y = readY(opcode);
     
     // TODO: implement tests
     if(state.v[y] > state.v[x])
@@ -206,7 +228,7 @@ void op8_func5(const uint16_t opcode) {
 
 // 8XY6
 void op8_func6(const uint16_t opcode) {
-    const uint8_t x = (opcode & 0x0f00) >> 8;
+    const auto x = readX(opcode);
     
     state.v[0xF] = (state.v[x] & 1);
     state.v[x] >>= 1;
@@ -230,8 +252,8 @@ void operation8(const uint16_t opcode) {
 
 // 9XY0
 void operation9(const uint16_t opcode) {
-    const uint8_t x = (opcode & 0x0f00) >> 8;
-    const uint8_t y = (opcode & 0x00f0) >> 4;
+    const auto x = readX(opcode);
+    const auto y = readY(opcode);
     
     if(state.v[x] != state.v[y])
         state.PC += 4;
@@ -241,7 +263,7 @@ void operation9(const uint16_t opcode) {
 
 // ANNN
 void operationA(const uint16_t opcode) {
-    const uint16_t nnn = opcode & 0x0fff;
+    const auto nnn = readAddress(opcode);
 
     state.I = nnn;
     state.PC += 2;
@@ -249,8 +271,8 @@ void operationA(const uint16_t opcode) {
 
 // CXNN
 void operationC(const uint16_t opcode) {
-    const uint8_t x = (opcode & 0x0f00) >> 8;
-    const uint8_t nn = opcode & 0x00ff;
+    const auto x = readX(opcode);
+    const auto nn = readNN(opcode);
 
     srand(time(nullptr));
     state.v[x] = (rand() % 0xFF) & nn;
@@ -259,9 +281,9 @@ void operationC(const uint16_t opcode) {
 
 // DXYN
 void operationD(const uint16_t opcode) {
-    const uint8_t x = (opcode & 0x0f00) >> 8;
-    const uint8_t y = (opcode & 0x00f0) >> 4;
-    const uint8_t n = opcode & 0x000f;
+    const auto x = readX(opcode);
+    const auto y = readY(opcode);
+    const auto n = readN(opcode);
 
     const uint8_t x_pos = state.v[x];
     const uint8_t y_pos = state.v[y];
@@ -295,7 +317,7 @@ void operationD(const uint16_t opcode) {
 
 // EX9E & EXA1
 void operationE(const uint16_t opcode) {
-    const uint8_t x = (opcode & 0x0f00) >> 8;
+    const auto x = readX(opcode);
 
     switch(opcode & 0x00ff) {
         case 0x9E:
@@ -319,7 +341,7 @@ void operationE(const uint16_t opcode) {
 
 // FX07
 void opF_func7(const uint16_t opcode) {
-    const uint8_t x = (opcode & 0x0f00) >> 8;
+    const auto x = readX(opcode);
 
     state.v[x] = state.delay_timer;
     
@@ -328,7 +350,7 @@ void opF_func7(const uint16_t opcode) {
 
 // FX0A
 void opF_funcA(const uint16_t opcode) {
-    const uint8_t x = (opcode & 0x0f00) >> 8;
+    const auto x = readX(opcode);
 
     for(int i = 0; i < 16; i++) {
         if(state.keys[i] != 0) {
@@ -340,7 +362,7 @@ void opF_funcA(const uint16_t opcode) {
 
 // FX55/FX65 & FX15
 void opF_func5(const uint16_t opcode) {
-    const uint8_t x = (opcode & 0x0f00) >> 8;
+    const auto x = readX(opcode);
 
     switch((opcode & 0x00F0) >> 4) {
         case 0x6:
@@ -377,25 +399,23 @@ void opF_func5(const uint16_t opcode) {
 
 // FX18
 void opF_func8(const uint16_t opcode) {
-    const uint8_t x = (opcode & 0x0f00) >> 8;
+    const auto x = readX(opcode);
 
     state.sound_timer = state.v[x];
-    
     state.PC += 2;
 }
 
 // FX29
 void opF_func9(const uint16_t opcode) {
-    const uint8_t x = (opcode & 0x0f00) >> 8;
+    const auto x = readX(opcode);
 
     state.I = state.v[x] * 0x5;
-    
     state.PC += 2;
 }
 
 // FX1E
 void opF_funcE(const uint16_t opcode) {
-    const uint8_t x = (opcode & 0x0f00) >> 8;
+    const auto x = readX(opcode);
 
     if((state.I + state.v[x]) > 0xFFF)
         state.v[15] = 1;
@@ -403,13 +423,12 @@ void opF_funcE(const uint16_t opcode) {
         state.v[15] = 0;
     
     state.I += state.v[x];
-    
     state.PC += 2;
 }
 
 // FX33
 void opF_func3(const uint16_t opcode) {
-    const uint8_t x = (opcode & 0x0f00) >> 8;
+    const auto x = readX(opcode);
     
     int decimal_rep = state.v[x];