diff --git a/AppLaser.java b/AppLaser.java
index dceba16..095dbc0 100644
--- a/AppLaser.java
+++ b/AppLaser.java
@@ -256,12 +256,20 @@ public class AppLaser {
 
                         int start_time = (int) Instant.now().getEpochSecond();
 
-                        while (!universe.isSolved()) {
+                        Stack bestStack = stack.copy();
+                        int best_filled_boxes = 0;
+                        int best_nb_mirrors = 0;
+
+                        do { //!universe.isSolved()
                             if (universe.canEvolve(currentState)) {
                                 stack.push(currentState.copy(universe.possibleChoices(currentState)));
                                 currentState = universe.evolve(currentState);
 
                                 if (display_progress == true) universe.print(universe_height + 6, 4);
+
+                                if (universe.getFilledBoxes() > best_filled_boxes && universe.getNbMirrors() < best_nb_mirrors) {
+                                    bestStack = stack.copy();
+                                }
                             }
                             else if (stack.size() > 0) {
                                 currentState = stack.pop();
@@ -278,7 +286,7 @@ public class AppLaser {
                             if ((int) Instant.now().getEpochSecond() - start_time > 2 * 60 && optimize_duration == true) {
                                 display_regress = false;
                             }
-                        }
+                        } while (stack.size() != 0);
 
                         System.out.println("\n\n");
 
diff --git a/Stack.java b/Stack.java
index 84dde3c..9a6e064 100644
--- a/Stack.java
+++ b/Stack.java
@@ -13,6 +13,10 @@ public class Stack <T> {
 		array = new Vector<T>();
 	}
 
+	public Stack(Vector<T> array) {
+		array = array;
+	}
+
 	// Methods
 
 	public void push(T x) {
@@ -28,4 +32,8 @@ public class Stack <T> {
 	public int size() {
 		return this.array.size();
 	}
+
+	public Stack copy() {
+		return new Stack(new Vector<T>(this.array));
+	}
 }
diff --git a/Universe.java b/Universe.java
index 588bff6..7099e2d 100644
--- a/Universe.java
+++ b/Universe.java
@@ -9,6 +9,9 @@ public class Universe {
     private int[][] grid;
     private int width, height;
     private int boxes_to_fill;
+    private int filled_boxes;
+    private int nb_mirors;
+    private String name;
 
     // Constructors
 
@@ -17,6 +20,8 @@ public class Universe {
         this.height = height;
         this.width = width;
         this.boxes_to_fill = (width - 2) * (height - 2) - 1;
+        this.filled_boxes = 0;
+        this.nb_mirors = 0;
 
         int i, j;
         for (i = 1; i < this.height - 1; i++) {
@@ -98,6 +103,17 @@ public class Universe {
         }
     }
 
+    public void recalculateBoxesToFill() {
+        this.boxes_to_fill = 0;
+        for (int i = 1; i < this.height - 1; i++) {
+            for (int j = 1; j < this.width - 1; j++) {
+                if ((this.grid[i - 1][j] == 0 || this.grid[i + 1][j] == 0 || this.grid[i][j - 1] == 0 || this.grid[i][j + 1] == 0) && this.grid[i][j] == 0) {
+                    this.boxes_to_fill ++;
+                }
+            }
+        }
+    }
+
     public void resetUniverse() {
         for (int i = 1; i < this.height - 1; i++) {
             for (int j = 1; j < this.width - 1; j++) {
@@ -106,6 +122,8 @@ public class Universe {
                 }
             }
         }
+
+        this.recalculateBoxesToFill();
     }
 
     public void resetUniverseObstacles() {
@@ -149,7 +167,7 @@ public class Universe {
         this.width = width;
         this.height = height;
 
-        this.boxes_to_fill = 0;
+        /*this.boxes_to_fill = 0;
 
         for (int i = 1; i < height - 1; i++) {
             for (int j = 1; j < width - 1; j++) {
@@ -157,7 +175,9 @@ public class Universe {
                     this.boxes_to_fill ++;
                 }
             }
-        }
+        }*/
+
+        this.recalculateBoxesToFill();
     }
 
     public void changeUniverseStart(int pos_i, int pos_j, int dir) {
@@ -175,7 +195,8 @@ public class Universe {
     public void addObstacle(int pos_i, int pos_j) {
         if (this.grid[pos_i][pos_j] == 0) {
             this.grid[pos_i][pos_j] = -1;
-            this.boxes_to_fill--;
+            //this.boxes_to_fill--;
+            this.recalculateBoxesToFill();
         }
         else {}
     }
@@ -284,21 +305,30 @@ public class Universe {
         if (c == 1 && (d == 10 || d == 11)) {
             if (this.grid[i][j] == 0) {
                 this.grid[i][j] = 1;
+                this.filled_boxes ++;
             } else {
                 this.grid[i][j] = 3;
-                this.boxes_to_fill++;
+                //this.boxes_to_fill++;
             }
         }
         if (c == 1 && (d == 12 || d == 13)) {
             if (this.grid[i][j] == 0) {
                 this.grid[i][j] = 2;
+                this.filled_boxes ++;
             } else {
                 this.grid[i][j] = 3;
-                this.boxes_to_fill++;
+                //this.boxes_to_fill++;
             }
         }
-        if ((c == 3 && d == 10) || (c == 3 && d == 11) || (c == 2 && d == 12) || (c == 2 && d == 13)) this.grid[i][j] = 4;
-        if ((c == 2 && d == 10) || (c == 2 && d == 11) || (c == 3 && d == 12) || (c == 3 && d == 13)) this.grid[i][j] = 5;
+        if ((c == 3 && d == 10) || (c == 3 && d == 11) || (c == 2 && d == 12) || (c == 2 && d == 13)) {
+            this.grid[i][j] = 4;
+            this.filled_boxes ++;
+            this.nb_mirors ++;
+        }
+        if ((c == 2 && d == 10) || (c == 2 && d == 11) || (c == 3 && d == 12) || (c == 3 && d == 13)) {
+            this.grid[i][j] = 5;
+            this.filled_boxes ++;
+        }
 
         // changing the position of the situation
 
@@ -370,4 +400,12 @@ public class Universe {
         }
         catch (Exception e) {}
     }
+
+    public int getFilledBoxes() {
+        return this.filled_boxes;
+    }
+
+    public int getNbMirrors() {
+        return this.nb_mirors;
+    }
 }