diff --git a/app/src/main/java/sudoku/Cell.java b/app/src/main/java/sudoku/Cell.java
index c7088a4..674e8f3 100644
--- a/app/src/main/java/sudoku/Cell.java
+++ b/app/src/main/java/sudoku/Cell.java
@@ -3,11 +3,11 @@ package sudoku;
 public abstract class Cell {
 
 	protected static int NOSYMBOLE = -1;
-	protected int symboleIndex;
+	protected int symbolIndex;
 	protected Block block = null;
 
-	public Cell(int symboleIndex) {
-		this.symboleIndex = symboleIndex;
+	public Cell(int symbolIndex) {
+		this.symbolIndex = symbolIndex;
 	}
 
 	/**
@@ -17,8 +17,8 @@ public abstract class Cell {
 		this(NOSYMBOLE);
 	}
 
-	public int getSymboleIndex() {
-		return symboleIndex;
+	public int getSymbolIndex() {
+		return symbolIndex;
 	}
 
 	public Block getBlock() {
@@ -33,7 +33,23 @@ public abstract class Cell {
 	@Override
 	public boolean equals(Object obj) {
 		if (obj instanceof Cell otherCell)
-			return otherCell.getSymboleIndex() == this.getSymboleIndex();
+			return otherCell.getSymbolIndex() == this.getSymbolIndex();
 		return false;
 	}
+
+	@Override
+	public String toString() {
+		StringBuilder sb = new StringBuilder();
+		sb.append("| ");
+		if (this.symbolIndex != NOSYMBOLE){
+			sb.append(this.symbolIndex);
+		}
+		else {
+			sb.append(" ");
+		}
+
+		sb.append(" |");
+		return sb.toString();
+	}
+
 }
diff --git a/app/src/main/java/sudoku/Coordinate.java b/app/src/main/java/sudoku/Coordinate.java
new file mode 100644
index 0000000..668dd85
--- /dev/null
+++ b/app/src/main/java/sudoku/Coordinate.java
@@ -0,0 +1,33 @@
+package sudoku;
+
+public class Coordinate {
+
+    private int x;
+    private int y;
+
+    public Coordinate(int row, int col) {
+        this.x = row;
+        this.y = col;
+    }
+
+    public int getX() {
+        return x;
+    }
+
+    public void setX(int x) {
+        this.x = x;
+    }
+
+    public int getY() {
+        return y;
+    }
+
+    public void setY(int y) {
+        this.y = y;
+    }
+
+    public int calculateIndex(int size) {
+        return this.y * size + this.x;
+    }
+
+}
diff --git a/app/src/main/java/sudoku/MultiDoku.java b/app/src/main/java/sudoku/MultiDoku.java
index 1e3a4e5..956f076 100644
--- a/app/src/main/java/sudoku/MultiDoku.java
+++ b/app/src/main/java/sudoku/MultiDoku.java
@@ -42,4 +42,20 @@ public class MultiDoku {
 		return mutableCells;
 	}
 
+	public void updateSymbolsPossibilities() throws Exception {
+		for (Sudoku sudoku : subGrids){
+			sudoku.updateSymbolsPossibilities();
+		}
+	}
+
+	@Override
+	public String toString() {
+		StringBuilder sb = new StringBuilder();
+		sb.append("Multidoku {");
+		for (Sudoku sudoku : subGrids){
+			sb.append("\n\t").append(sudoku.toString());
+		}
+		sb.append("\n}");
+		return sb.toString();
+	}
 }
diff --git a/app/src/main/java/sudoku/MutableCell.java b/app/src/main/java/sudoku/MutableCell.java
index ab99658..7994627 100644
--- a/app/src/main/java/sudoku/MutableCell.java
+++ b/app/src/main/java/sudoku/MutableCell.java
@@ -5,33 +5,38 @@ import java.util.List;
 
 public class MutableCell extends Cell{
 
-	private final List<Integer> hintsSymbolIndex;
+	private final List<Integer> possibleSymbols;
 
 	public MutableCell() {
 		super();
-		this.hintsSymbolIndex = new ArrayList<>();
+		this.possibleSymbols = new ArrayList<>();
 	}
 
-	public MutableCell(int symboleIndex) {
-		super(symboleIndex);
-		this.hintsSymbolIndex = new ArrayList<>();
+	public MutableCell(int symbolIndex) {
+		super(symbolIndex);
+		this.possibleSymbols = new ArrayList<>();
 	}
 
-	public void setSymboleIndex(int symboleIndex) {
-		this.symboleIndex = symboleIndex;
+	public void setSymbolIndex(int symbolIndex) {
+		this.symbolIndex = symbolIndex;
 	}
 
-	public void clear() {
-		setSymboleIndex(NOSYMBOLE);
+	/**
+	 * Remove the current symbolIndex and returns it
+	 * @return integer symbolIndex cleared
+	 */
+	public int clearCurrentSymbol() {
+		int i = this.symbolIndex;
+		setSymbolIndex(NOSYMBOLE);
+		return i;
 	}
 
-	public void clear(int indexSymbol) {
-		hintsSymbolIndex.remove(indexSymbol);
-		this.clear();
+	public void removeSymbolFromPossibilities(int indexSymbol) {
+		possibleSymbols.remove(indexSymbol);
 	}
 
-	public List<Integer> getHints() {
-		return this.hintsSymbolIndex;
+	public List<Integer> getPossibleSymbols() {
+		return this.possibleSymbols;
 	}
 
 }
diff --git a/app/src/main/java/sudoku/Sudoku.java b/app/src/main/java/sudoku/Sudoku.java
index 3b60963..80ab687 100644
--- a/app/src/main/java/sudoku/Sudoku.java
+++ b/app/src/main/java/sudoku/Sudoku.java
@@ -14,10 +14,12 @@ public class Sudoku {
 
 	private final List<Block> blocks;
 	private final List<Cell> cells;
+	private final List<IConstraint> constraints;
 
-	public Sudoku(List<Cell> cells, List<Block> blocks) {
+	public Sudoku(List<Cell> cells, List<Block> blocks, List<IConstraint> constraints) {
 		this.cells = cells;
 		this.blocks = blocks;
+		this.constraints = new ArrayList<>(constraints);
 	}
 
 	public Cell getCell(int x, int y) {
@@ -30,6 +32,10 @@ public class Sudoku {
 		return this.cells.get(i);
 	}
 
+	public List<IConstraint> getConstraints() {
+		return constraints;
+	}
+
 	public int getSize() {
 		return this.blocks.size();
 	}
@@ -49,4 +55,64 @@ public class Sudoku {
 		}
 		return mutableCells;
 	}
+
+	public boolean contains(Cell cell) {
+		return this.cells.contains(cell);
+	}
+
+	private Coordinate getCoordinateCell(Cell c) throws Exception {
+		int x=0, y=0;
+		int size = this.getSize();
+
+		if (!this.contains(c)) {
+			throw new Exception("The given cell is not in this sudoku.");
+		}
+
+		for (Cell cell : this.cells) {
+			if (cell == c){
+				return new Coordinate(x, y);
+			}
+			if (x == size - 1){
+				y+=1;
+				x=0;
+			}
+			else {
+				x+=1;
+			}
+		}
+		return new Coordinate(x, y);
+	}
+
+    public void updateSymbolsPossibilities() throws Exception {
+		for (IConstraint constraint : constraints) {
+			List<MutableCell> mutableCells = this.getMutableCells();
+			for (MutableCell cell : mutableCells) {
+                Coordinate coord = null;
+                try {
+                    coord = this.getCoordinateCell(cell);
+                } catch (Exception e) {
+                    throw new RuntimeException(e);
+                }
+                constraint.getPossibleSymbols(this, coord.getX(), coord.getY());
+				if (cell.getPossibleSymbols().isEmpty()){
+					throw new Exception("Rollback bitch");
+				}
+			}
+		}
+	}
+
+	public String toString (){
+		StringBuilder sb = new StringBuilder();
+		sb.append("Sudoku {");
+		for (int i = 0; i < getSize(); i++) {
+			sb.append("\n\t");
+			for (int j = 0; j < getSize(); j++) {
+				Cell cell = getCell(i, j);
+				sb.append(cell.toString()).append(" ");
+			}
+		}
+		sb.append("\n}");
+		return sb.toString();
+	}
+
 }
diff --git a/app/src/main/java/sudoku/SudokuFactory.java b/app/src/main/java/sudoku/SudokuFactory.java
index dde6f27..dfb0222 100644
--- a/app/src/main/java/sudoku/SudokuFactory.java
+++ b/app/src/main/java/sudoku/SudokuFactory.java
@@ -1,5 +1,10 @@
 package sudoku;
 
+import sudoku.constraint.BlockConstraint;
+import sudoku.constraint.ColumnConstraint;
+import sudoku.constraint.IConstraint;
+import sudoku.constraint.LineConstraint;
+
 import java.util.ArrayList;
 import java.util.List;
 
@@ -33,14 +38,18 @@ public class SudokuFactory {
 		return blocs;
 	}
 
-	public static MultiDoku createBasicEmptyRectangleSudoku(int width, int height) {
-		int symbolCount = width * height;
+	public static MultiDoku createBasicEmptyRectangleSudoku(int widthBlock, int heightBlock) {
+		int symbolCount = widthBlock * heightBlock;
 		List<Cell> cases = initCells(symbolCount);
-		List<Block> blocs = initRectangleBlocs(cases, width, height);
-		Sudoku s = new Sudoku(cases, blocs);
-		List<Sudoku> ss = new ArrayList<>();
-		ss.add(s);
-		return new MultiDoku(ss);
+		List<Block> blocs = initRectangleBlocs(cases, widthBlock, heightBlock);
+		List<IConstraint> constraints = new ArrayList<>();
+		constraints.add(new ColumnConstraint());
+		constraints.add(new LineConstraint());
+		constraints.add(new BlockConstraint());
+		Sudoku s = new Sudoku(cases, blocs, constraints);
+		List<Sudoku> subSudoku = new ArrayList<>();
+		subSudoku.add(s);
+		return new MultiDoku(subSudoku);
 	}
 
 	public static MultiDoku createBasicEmptySquareSudoku(int size) {
diff --git a/app/src/main/java/sudoku/constraint/BlockConstraint.java b/app/src/main/java/sudoku/constraint/BlockConstraint.java
index a600a99..a0fe7c5 100644
--- a/app/src/main/java/sudoku/constraint/BlockConstraint.java
+++ b/app/src/main/java/sudoku/constraint/BlockConstraint.java
@@ -2,6 +2,7 @@ package sudoku.constraint;
 
 import sudoku.Block;
 import sudoku.Cell;
+import sudoku.MutableCell;
 import sudoku.Sudoku;
 
 public class BlockConstraint implements IConstraint{
@@ -9,7 +10,7 @@ public class BlockConstraint implements IConstraint{
 	@Override
 	public boolean canBePlaced(final Sudoku s, int x, int y, int newSymbolIndex) {
 		Block bloc = s.getCell(x, y).getBlock();
-		return !bloc.getCells().contains(new Cell(newSymbolIndex) {});
+		return !bloc.getCells().contains(new MutableCell(newSymbolIndex));
 	}
 
 }
diff --git a/app/src/main/java/sudoku/constraint/ColumnConstraint.java b/app/src/main/java/sudoku/constraint/ColumnConstraint.java
index 4c74ef2..881faab 100644
--- a/app/src/main/java/sudoku/constraint/ColumnConstraint.java
+++ b/app/src/main/java/sudoku/constraint/ColumnConstraint.java
@@ -7,7 +7,7 @@ public class ColumnConstraint implements IConstraint {
 	@Override
 	public boolean canBePlaced(final Sudoku s, int x, int y, int newSymbolIndex) {
 		for (int i = 0; i < s.getSize(); i++) {
-			if (s.getCell(x, newSymbolIndex).getSymboleIndex() == newSymbolIndex)
+			if (s.getCell(x, newSymbolIndex).getSymbolIndex() == newSymbolIndex)
 				return false;
 		}
 		return true;
diff --git a/app/src/main/java/sudoku/constraint/LineConstraint.java b/app/src/main/java/sudoku/constraint/LineConstraint.java
index 8837229..2f9a81e 100644
--- a/app/src/main/java/sudoku/constraint/LineConstraint.java
+++ b/app/src/main/java/sudoku/constraint/LineConstraint.java
@@ -7,7 +7,7 @@ public class LineConstraint implements IConstraint {
 	@Override
 	public boolean canBePlaced(final Sudoku s, int x, int y, int newSymbolIndex) {
 		for (int i = 0; i < s.getSize(); i++) {
-			if (s.getCell(newSymbolIndex, y).getSymboleIndex() == newSymbolIndex)
+			if (s.getCell(newSymbolIndex, y).getSymbolIndex() == newSymbolIndex)
 				return false;
 		}
 		return true;
diff --git a/app/src/main/java/sudoku/solver/Solver.java b/app/src/main/java/sudoku/solver/Solver.java
index 9f4376f..b87425c 100644
--- a/app/src/main/java/sudoku/solver/Solver.java
+++ b/app/src/main/java/sudoku/solver/Solver.java
@@ -1,17 +1,16 @@
 package sudoku.solver;
 
-import sudoku.Cell;
 import sudoku.MultiDoku;
 import sudoku.MutableCell;
-import sudoku.Sudoku;
 import sudoku.constraint.IConstraint;
 
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Random;
+import java.util.Stack;
 
 public class Solver {
-    Caretaker stack;
+    Stack<MutableCell> stack;
 
     public Solver() {
     }
@@ -26,12 +25,26 @@ public class Solver {
         while (!remainingCellsToCheck.isEmpty()) {
             int indexCurrentCell = rand.nextInt(remainingCellsToCheck.size());
             MutableCell currentCell = remainingCellsToCheck.get(indexCurrentCell);
-            if (currentCell.getHints().isEmpty()){
-                MutableCell modify = allMutableCells.get(stack.undo());
-                modify.clear(modify.getSymboleIndex());
+            if (currentCell.getPossibleSymbols().isEmpty()){
+                MutableCell modify = stack.pop();
+                modify.removeSymbolFromPossibilities(modify.clearCurrentSymbol());
+            } else {
+                int symbol = currentCell.getPossibleSymbols().get(0);
+                currentCell.setSymbolIndex(symbol);
+                stack.push(currentCell);
+                try {
+                    doku.updateSymbolsPossibilities();
+                } catch (Exception e) {
+                    //TODO rollback
+                }
+                //TODO check constraints integrity in sudoku
+
+
             }
 
 
+
+
             remainingCellsToCheck.remove(indexCurrentCell);
         }
         return doku;