diff --git a/src/main.c b/src/main.c
index 882cfd4..3a6fae8 100644
--- a/src/main.c
+++ b/src/main.c
@@ -26,17 +26,20 @@
 
 
 
-
+/* Player data (defined in "player.h")*/
 struct Player MyPlayer = { 10, 5, 100 };
 
 
-bool exittoOS = false;
+/* some global variables */
+bool exittoOS = false;		// set to true when asked for exit
 
-bool screenshot = false;
-bool record = false;
+bool screenshot = false;	// set to true when screenshot is required
+bool record = false;		// set to true when 
 
 
 
+/* Key management */
+
 static void get_inputs( void  )
 {
     key_event_t ev;
@@ -51,13 +54,14 @@ static void get_inputs( void  )
 
     if(keydown(KEY_EXIT)) exittoOS = true;
 
+	/* Player actions - Prototypes in player.h and implementation in player.c */
     if(keydown(KEY_LEFT))  PlayerLeft();
 	if(keydown(KEY_RIGHT)) PlayerRight();
 	if(keydown(KEY_UP))	   PlayerUp();
 	if(keydown(KEY_DOWN))  PlayerDown();
 	if(keydown(KEY_SHIFT)) PlayerAction();
 
-
+	/* if USB is enabled - keybinding for screencapture */
 
 #if USB_FEATURE==1
 
@@ -68,6 +72,8 @@ static void get_inputs( void  )
 }
 
 
+/* screen capture management code */
+
 #if USB_FEATURE==1
 
 	void USB_feature( void )
@@ -91,6 +97,11 @@ static void get_inputs( void  )
 #endif
 
 
+void GameLogic( void )
+{
+
+
+}
 
 
 int main(void)
@@ -102,8 +113,8 @@ int main(void)
 	#endif
 
 
-	dclear(C_WHITE);
-	
+	/* start grayscale engine */
+
 	#ifdef COLOR2BIT
 		dgray( DGRAY_ON );
 	#endif
@@ -111,27 +122,38 @@ int main(void)
 
 	do
 	{
-		
+		/* clear screen */
+		dclear(C_WHITE);
+
+		/* render the map */
 		RenderMap();
 
+		/* start the logic of the game */
+		GameLogic();
+
+		/* Screen blit */
 		dupdate();
 
+		/* Screen capture feature if enabled */
 		#if USB_FEATURE==1
 			USB_feature();
 		#endif
 
+		/* Management of the inputs */
 		get_inputs();
 
 	}
-	while (exittoOS == false);
-
+	while (exittoOS == false);	// want to exit ?
 
 
 
+	/* shutdown grayengine*/
 	#ifdef COLOR2BIT
 		dgray( DGRAY_OFF );
 	#endif
 
+
+	/* close USB */
 	#if USB_FEATURE==1
   		usb_close();
 	#endif
diff --git a/src/map.c b/src/map.c
index da9f948..0f184d1 100644
--- a/src/map.c
+++ b/src/map.c
@@ -7,18 +7,29 @@ struct Map *map_level = &map_level0;
 
 void RenderMap( void )
 {
+  /* for all Layer (2 in the current configuration: Background is layer 0 and foreground is layer 1 ) */
   for (int u = 0; u < map_level->nblayers; u++)
   {
+    /* for each colum */
     for (int i = 0; i < map_level->w; i++)
     {
+      /* and each line */
       for (int j = 0; j < map_level->h; j++)
       {
+        /* compute the index */
         uint16_t index = j * map_level->w + i;
+        
+        /* get the tile index from the map*/
         int16_t currentTile = map_level->layers[u][index];
+        
+        /* currentTile == -1 means nothing to be draw */
         if (currentTile != -1)
         {
+          /* get x and y position in the tileset image */
           uint16_t xtile = (currentTile % map_level->tileset_size) * 8;
           uint16_t ytile = (currentTile / map_level->tileset_size) * 8;
+          
+          /* render */
           dsubimage(i * 8, j * 8, map_level->tileset, xtile, ytile, 8, 8, DIMAGE_NONE );
         }
       }
diff --git a/src/map.h b/src/map.h
index 0667bc2..2a0332e 100644
--- a/src/map.h
+++ b/src/map.h
@@ -9,6 +9,7 @@ void RenderMap(void);
 
 
 struct Map {
+
   /*width, height and the number of layer of the map*/
   int w, h, nblayers;
 
diff --git a/src/player.h b/src/player.h
index 094cc99..a9a3f49 100644
--- a/src/player.h
+++ b/src/player.h
@@ -4,7 +4,7 @@
 #include <stdint.h>
 
 
-
+/* Struct that define player parameters */
 struct Player
 {
     uint16_t x, y;