diff --git a/sources/PPU/Background.cpp b/sources/PPU/Background.cpp
index f21406c..e7a8344 100644
--- a/sources/PPU/Background.cpp
+++ b/sources/PPU/Background.cpp
@@ -29,18 +29,18 @@ namespace ComSquare::PPU
 	{
 		uint16_t vramAddress = this->_TileMapStartAddress;
 		Vector2<int> offset(0, 0);
-		this->backgroundSize.x = this->_tileMaps.x * this->_characterSize.x * 32;
-		this->backgroundSize.y = this->_tileMaps.y * this->_characterSize.y * 32;
+		this->backgroundSize.x = this->_tileMaps.x * this->_characterSize.x * NB_CHARACTER_WIDTH;
+		this->backgroundSize.y = this->_tileMaps.y * this->_characterSize.y * NB_CHARACTER_HEIGHT;
 
 		for (int i = 0; i < 4; i++) {
 			if (!(i == 1 && this->_tileMaps.x == 1) && !(i > 1 && this->_tileMaps.y == 1)) {
 				drawBasicTileMap(vramAddress, offset);
 			}
-			vramAddress+= 0x800;
-			offset.x += 32 * this->_characterSize.x;
+			vramAddress += 0x800;
+			offset.x += NB_CHARACTER_WIDTH * this->_characterSize.x;
 			if (i == 2) {
 				offset.x = 0;
-				offset.y += 32 * this->_characterSize.y;
+				offset.y += NB_CHARACTER_HEIGHT * this->_characterSize.y;
 			}
 		}
 	}
@@ -57,7 +57,9 @@ namespace ComSquare::PPU
 		tileData.raw = data;
 		palette = getPalette(tileData.palette);
 		// TODO explain X and Y and rethink the formula
-		graphicAddress = this->_tileSetAddress + (tileData.posX * 16 * this->_bpp * 8) + (tileData.posY * this->_bpp * 8);
+		// X horizontal
+		// Y vertical
+		graphicAddress = this->_tileSetAddress + (tileData.posY * 16 * this->_bpp * 8) + (tileData.posX * this->_bpp * 8);
 		for (int i = 0; i < this->_characterSize.y; i++) {
 			for (int j = 0; j < this->_characterSize.x; j++) {
 				reference = getTilePixelReference(graphicAddress, index);
@@ -129,6 +131,7 @@ namespace ComSquare::PPU
 		uint16_t vramAddress = baseAddress;
 
 		while (vramAddress < baseAddress + 0x800) {
+			// TODO function to read 2 bytes (LSB order or bits reversed)
 			tileMapValue = this->_vram->read_internal(vramAddress);
 			tileMapValue += this->_vram->read_internal(vramAddress + 1) << 8U;
 			drawBgTile(tileMapValue, {(pos.x * this->_characterSize.x) + offset.x, (pos.y * this->_characterSize.y) + offset.y});
diff --git a/sources/PPU/Background.hpp b/sources/PPU/Background.hpp
index 32c94c4..994d744 100644
--- a/sources/PPU/Background.hpp
+++ b/sources/PPU/Background.hpp
@@ -19,6 +19,8 @@ namespace ComSquare::PPU
 {
 	class PPU;
 	class Background {
+	#define NB_CHARACTER_WIDTH 32
+	#define NB_CHARACTER_HEIGHT 32
 	private:
 		Vector2<int> _tileMaps;
 		Vector2<int> _characterSize;
@@ -39,6 +41,7 @@ namespace ComSquare::PPU
 		//! @brief draw a tilemap 32x32 starting at baseAddress
 		void drawBasicTileMap(uint16_t baseAddress, Vector2<int> offset);
 	public:
+		// TODO getter setter for priority and bgNumber
 		bool priority;
 		int bgNumber;
 		Vector2<int> backgroundSize;
diff --git a/sources/PPU/PPU.cpp b/sources/PPU/PPU.cpp
index 6ecd720..c19c735 100644
--- a/sources/PPU/PPU.cpp
+++ b/sources/PPU/PPU.cpp
@@ -38,7 +38,7 @@ namespace ComSquare::PPU
 		//colors for the cgram
 		this->cgram->write_internal(2, 0xE0);
 		this->cgram->write_internal(3, 0x7F);
-		this->cgram->write_internal(4, 0x0F); // 0x1F
+		this->cgram->write_internal(4, 0x1F); // 0x1F
 		this->cgram->write_internal(6, 0xFF);
 		this->cgram->write_internal(7, 0x03);
 		this->cgram->write_internal(66, 0xE0);
@@ -129,6 +129,7 @@ namespace ComSquare::PPU
 
 	uint8_t PPU::read(uint24_t addr)
 	{
+		return 0;
 		switch (addr) {
 		case ppuRegisters::mpyl:
 			return  this->_registers._mpy.mpyl;
@@ -157,6 +158,7 @@ namespace ComSquare::PPU
 
 	void PPU::write(uint24_t addr, uint8_t data)
 	{
+		return;
 		switch (addr) {
 		case ppuRegisters::inidisp:
 			this->_registers._inidisp.raw = data;
diff --git a/sources/PPU/PPUUtils.hpp b/sources/PPU/PPUUtils.hpp
index 16d90e3..80ee33a 100644
--- a/sources/PPU/PPUUtils.hpp
+++ b/sources/PPU/PPUUtils.hpp
@@ -11,8 +11,8 @@ namespace ComSquare::PPU
 {
 	union TileMapData {
 		struct {
-			uint8_t posY: 4;
-			uint8_t posX: 6;
+			uint8_t posX: 4;
+			uint8_t posY: 6;
 			uint8_t palette: 3;
 			bool tilePriority: 1;
 			bool horizontalFlip: 1;