diff --git a/core/src/fr/evolving/automata/Cell.java b/core/src/fr/evolving/automata/Cell.java
index c43ec82..ee5955e 100644
--- a/core/src/fr/evolving/automata/Cell.java
+++ b/core/src/fr/evolving/automata/Cell.java
@@ -2,12 +2,13 @@ package fr.evolving.automata;
 
 import java.io.Serializable;
 
-public class Cell implements Serializable {
+public class Cell implements Serializable,Cloneable {
 	public int Fiber;
 	public boolean Copper;
+	public Transmuter Transmuter;
+	
 	public transient int Copper_calc;
 	public transient int Fiber_old;
-	public Transmuter Transmuter;
 	public transient int Transmuter_calc;
 	public transient int Transmuter_movex;
 	public transient int Transmuter_movey;
@@ -21,5 +22,13 @@ public class Cell implements Serializable {
 		this.Transmuter_movex = 0;
 		this.Transmuter_movey = 0;
 	}
-
+	
+	public Object clone() {
+		Cell result = new Cell();
+		result.Copper=this.Copper;
+		result.Fiber=this.Fiber;
+		if (this.Transmuter!=null)
+			result.Transmuter=(Transmuter)this.Transmuter.clone();
+		return result;
+	}
 }
diff --git a/core/src/fr/evolving/automata/Grid.java b/core/src/fr/evolving/automata/Grid.java
index 6d19483..7c8a4d9 100644
--- a/core/src/fr/evolving/automata/Grid.java
+++ b/core/src/fr/evolving/automata/Grid.java
@@ -7,7 +7,7 @@ import com.badlogic.gdx.Gdx;
 import com.badlogic.gdx.math.Vector2;
 import com.badlogic.gdx.utils.ObjectMap.Entry;
 
-public class Grid implements Serializable {
+public class Grid implements Serializable,Cloneable {
 	public Cell[][] Cells;
 	public Integer sizeX, sizeY;
 
@@ -269,5 +269,13 @@ public class Grid implements Serializable {
 		else
 			return cell.Copper_calc;
 	}
+	
+	public Object clone() {
+		Grid result = new Grid(this.sizeX,this.sizeY);
+		for (int x = 0; x < this.sizeX; x++)
+			for (int y = 0; y < this.sizeY; y++)
+				result.Cells[x][y] = (Cell)this.Cells[x][y].clone();
+		return result;
+	}
 
 }
diff --git a/core/src/fr/evolving/automata/Worlds.java b/core/src/fr/evolving/automata/Worlds.java
index 030ac6f..e9bdb1d 100644
--- a/core/src/fr/evolving/automata/Worlds.java
+++ b/core/src/fr/evolving/automata/Worlds.java
@@ -166,14 +166,14 @@ public class Worlds extends Actor {
 		ReadLastGrid();
 		if (usedlevel.Grid == null || force) {
 			Gdx.app.debug(getClass().getSimpleName(), "Copie monde original.");
-			usedlevel.Grid = usedlevel.Grid_orig;
+			usedlevel.Grid = (Grid)usedlevel.Grid_orig.clone();
 
 		} else {
-			Gdx.app.debug(getClass().getSimpleName(),
-					"Récupération de la dernière grille.");
-			usedlevel.Grid.tiling_copper();
-			usedlevel.Grid.tiling_transmuter();
+			Gdx.app.debug(getClass().getSimpleName(),"Récupération de la dernière grille.");
+			ReadLastGrid();
 		}
+		usedlevel.Grid.tiling_copper();
+		usedlevel.Grid.tiling_transmuter();
 	}
 	
 	public void setLevel(int alevel) {
diff --git a/core/src/fr/evolving/screens/LevelScreen.java b/core/src/fr/evolving/screens/LevelScreen.java
index 7fb1640..caf3d1c 100644
--- a/core/src/fr/evolving/screens/LevelScreen.java
+++ b/core/src/fr/evolving/screens/LevelScreen.java
@@ -201,7 +201,9 @@ public class LevelScreen implements Screen {
 			}
 		buttonLevels = null;
 		buttonLevels = new ButtonLevel[10];
-		for (Level level : worlds.getLevels()) {
+		Array<Level> levels=worlds.getLevels();
+		if (levels!=null)
+		for (Level level : levels) {
 			if (level != null) {
 				if (level.Name.isEmpty())
 					level.Name=AssetLoader.language.get("[level"+(level.aWorld+1)+"/"+(level.aLevel+1)+"-name]");
@@ -268,15 +270,17 @@ public class LevelScreen implements Screen {
 						}
 					if (worlds.getInformations()==null)
 						selected=buttonLevels[0];
-					selected.setChecked(true);
-					showlevel(selected);
+					if (selected!=null) {
+						selected.setChecked(true);
+						buttonPlay.setVisible(true);
+						TextDescriptive.setVisible(true);
+						showlevel(selected);
+					}
 					Previous.setVisible(!worlds.isFirstWorld());
 					if (worlds.isDebug())
 						Next.setVisible(!worlds.isRealLastWorld());
 					else
 						Next.setVisible(!worlds.isLastWorld());
-					buttonPlay.setVisible(true);
-					TextDescriptive.setVisible(true);
 				}
 				else {
 					Previous.setVisible(false);
@@ -623,8 +627,9 @@ public class LevelScreen implements Screen {
 	}
 
 	public void showlevel(ButtonLevel button) {
-		Gdx.app.debug(getClass().getSimpleName(), "Reading button "
-				+ button.level.Name);
+		if (button==null)
+			return;
+		Gdx.app.debug(getClass().getSimpleName(), "Reading button "	+ button.level.Name);
 		TextDescriptive.setText(button.level.Description);
 		if (button.level.Maxcycle < 99999 && button.level.Maxcycle > 0) {
 			cycle.setText(String.valueOf(button.level.Maxcycle));