diff --git a/src/map.cpp b/src/map.cpp
index 12692cd..e14baba 100644
--- a/src/map.cpp
+++ b/src/map.cpp
@@ -1,5 +1,6 @@
 #include "map.h"
 #include <glm/vec3.hpp>
+#include "string.h"
 
 Map::Map(int nbTeams, int width, int height) :
     m_width(width),
@@ -21,3 +22,14 @@ Map::~Map()
     if(m_nbTeams)
         delete m_teams;
 }
+
+void Pixel::readBook(Com &msg)
+{
+    //why the fuck +sizeof(int) ? u_u
+    memcpy(msg.data + sizeof(int), data.knowledge + (msg.flag | 3), COM_SIZE);
+}
+
+void Pixel::writeBook(const Com &msg)
+{
+    memcpy(data.knowledge + msg.flag, msg.data, COM_SIZE);
+}
diff --git a/src/map.h b/src/map.h
index ab47b65..4ecfdea 100644
--- a/src/map.h
+++ b/src/map.h
@@ -1,8 +1,9 @@
 #ifndef MAP_H
 #define MAP_H
 
-#include "pixeltype.h"
-#include "coord.h"
+//#include "pixeltype.h"
+//#include "coord.h"
+#include "behavior.h"
 
 class Dude;
 
@@ -19,6 +20,12 @@ struct Pixel
     PixelData data;
     
     Pixel() : type(GRASS) {}
+    /* The two following function are used to read and write
+     * from book in a library.
+     * msg should be the incoming message which asked for reading/writing
+    */
+    void readBook(Com &msg);
+    void writeBook(const Com &msg);
 };
 
 class Map
@@ -69,7 +76,7 @@ public:
     {
         // this is the shader implementation of the toreiller
         Coord nbRevolutions(c.x/m_width, c.y/m_height);
-        if(abs(nbRevolutions.y % 2))
+        if(std::abs(nbRevolutions.y % 2))
         {
             c.x += m_width/2;
             nbRevolutions.x = c.x/m_width;
diff --git a/src/pixeltype.h b/src/pixeltype.h
index 1f04080..ceb0a97 100644
--- a/src/pixeltype.h
+++ b/src/pixeltype.h
@@ -11,17 +11,11 @@ enum PixelType {
 
 struct PixelProperty
 {
-    //we might have to place these function elsewhere ?
     static bool isWalkable(PixelType target)
     {
-        return target != WALL
-            && target != ROCK
-            && target != BEDROCK
-            && target != IRON_ORE
-            && target != TREE
-            && target != LIBRARY
-            && target != DUDE
-            && target != SPAWN;
+        return target == GRASS
+            || target == ROAD
+            || target == MARK;
     }
     
     static bool isDestructible(PixelType target)
diff --git a/src/simulation.cpp b/src/simulation.cpp
index fd71e5f..ac948ca 100644
--- a/src/simulation.cpp
+++ b/src/simulation.cpp
@@ -37,22 +37,23 @@ void Simulation::update()
         if(t.updateSpawn())
         {
             Coord spawnPos = p_map->team(i) + Coord(Dir(rand()%4));
+            std::cout << p_map->getPixel(spawnPos).type << std::endl;
             if(PixelProperty::isWalkable(p_map->getPixel(spawnPos).type))
             {
                 Dude *dude = new Dude(spawnPos,p_map,i);
                 (*p_map)[spawnPos].data.dudePtr = dude;
                 p_map->updatePixel(spawnPos);
                 m_dudes.push_back(dude);
-            }/*
+            }
             else
-                // TODO delay the spawning
-            */
+                std::cout << "Unpopable" << std::endl;
+                // TODO check other case or delay the spawning
         }
     }
 }
 
-void Simulation::handleAction(const Action &action, Dude *dude){
-
+void Simulation::handleAction(const Action &action, Dude *dude)
+{
     // initialisation
     Coord currentPos(dude->getPos());
     Coord targetPos = p_map->toreillerLoop(currentPos + Coord(action.dir));
@@ -85,7 +86,7 @@ void Simulation::handleAction(const Action &action, Dude *dude){
         }
         break;
     case Action::PICK: // DONE
-        if(PixelProperty::isResource(target.type) && dude->getInventory() == -1){
+        if(PixelProperty::isResource(target.type) && dude->getInventory() == EMPTY){
             dude->setInventory(target.type);
             --target.data.nbRes;
             if(target.data.nbRes < 1)
@@ -97,13 +98,13 @@ void Simulation::handleAction(const Action &action, Dude *dude){
         }
         break;
     case Action::PUT: // DONE
-        if(dude->getInventory() != -1
+        if(dude->getInventory() != EMPTY
            && (target.type == GRASS || target.type == MARK || target.type == dude->getInventory())
            && target.data.nbRes < MAX_RESOURCES_IN_STACK)
         {
             if(target.type == GRASS || target.type == MARK)
             {
-                target.type = PixelType(dude->getInventory());
+                target.type = dude->getInventory();
                 target.data.nbRes = 1;
                 p_map->updatePixel(targetPos);
             }
@@ -184,10 +185,11 @@ void Simulation::handleAction(const Action &action, Dude *dude){
         switch(target.type){
         case DUDE:
         {
-            // WTF ? -> action.com_data.flag = (action.dir+2)%4;
+            Com msg(action.com_data);
+            msg.flag = (action.dir+2)%4; //show the source direction of the message
             Dude *targetDude = target.data.dudePtr;
             if(targetDude->getCom().data == NULL){
-                targetDude->receiveComData(action.com_data);
+                targetDude->receiveComData(msg);
                 dude->setSuccess(true);
             }else
                 dude->setSuccess(false);
@@ -198,10 +200,10 @@ void Simulation::handleAction(const Action &action, Dude *dude){
             {
                 if(dude->getCom().data == NULL)
                 {
-                    // WTF ? -> action.com_data.flag = action.dir;
-                    dude->receiveComData(action.com_data);
-                    // TODO: understand what the fuck this line is doing
-                    //memcpy(dude->getCom() + sizeof(int), target.data.knowledge + (action->com_data.flag | 3), COM_SIZE);
+                    Com msg(action.com_data);
+                    target.readBook(msg);
+                    msg.flag = action.dir; // dude is receiving information from where he asked to read
+                    dude->receiveComData(msg);
                 }
                 else
                 {
@@ -210,6 +212,7 @@ void Simulation::handleAction(const Action &action, Dude *dude){
                 }
             }
             else{
+                target.writeBook(action.com_data);
                 // TODO: understand what the fuck this line is doing bis
                 //memcpy(target.data.knowledge + action->com_data.flag, action->com_data.data, COM_SIZE);
                 dude->setSuccess(true);