diff --git a/README.md b/README.md
new file mode 100644
index 0000000..11aaec0
--- /dev/null
+++ b/README.md
@@ -0,0 +1,71 @@
+Morpion
+=======
+
+Diagramme de classes
+====================
+
+```mermaid
+classDiagram
+    class Position {
+        -x : int
+        -y : int
+        +x() int
+        +y() int
+    }
+
+    class Board {
+        -width : int
+        -height : int
+        +place(p : Placed)
+        +isOccupied() bool
+        +get(p : Position) Tile
+        +isBound(p : Position) bool
+        +isFull() bool
+    }
+    class Tile {
+    }
+    <<interface>> Tile
+    Empty <|-- Tile
+    Placed <|-- Tile
+    class Placed {
+        -value : char
+        +value() char
+    }
+    Tile "*" <-- Board
+    
+    class Game {
+        -board : Board
+        -players : List~Player~
+        -currentPlayer : int
+        +board() Board
+        +currentPlayer() Player
+        +nextPlayer()
+        +placeCurrent(p : Position) MoveResult
+        +players() List~Player~
+    }
+    Board <-- Game
+    
+    class MoveResult {
+    }
+    <<interface>> MoveResult
+    class Result {
+        -wins : List~Win~
+    }
+    class CantPlace {
+    }
+    Result <|-- MoveResult
+    CantPlace <|-- MoveResult
+    class Win {
+        -positions : List~Position~
+        +positions() List~Position~
+    }
+    
+    class WinChecker {   
+        +detectFrom(b : Board, p : Position) List~Win~ 
+    }
+    <<interface>> WinChecker
+    Win <.. WinChecker
+    Position <.. Win
+    Position <.. Board
+    MoveResult <.. Game
+```
\ No newline at end of file
diff --git a/src/main/java/fr/uca/iut/clfreville2/morpion/cli/CliPlay.java b/src/main/java/fr/uca/iut/clfreville2/morpion/cli/CliPlay.java
index cca1c80..4cd6353 100644
--- a/src/main/java/fr/uca/iut/clfreville2/morpion/cli/CliPlay.java
+++ b/src/main/java/fr/uca/iut/clfreville2/morpion/cli/CliPlay.java
@@ -23,6 +23,7 @@ public class CliPlay {
                 .mapToObj(i -> new Player("Player" + i))
                 .toList();
         game = new Game(players.toArray(Player[]::new));
+        game.start();
 
         final AsciiBoardFormatter formatter = new AsciiBoardFormatter();
         while (!isGameOver() && !game.board().isFull()) {
diff --git a/src/main/java/fr/uca/iut/clfreville2/morpion/game/Game.java b/src/main/java/fr/uca/iut/clfreville2/morpion/game/Game.java
index b429e4a..eb8a837 100644
--- a/src/main/java/fr/uca/iut/clfreville2/morpion/game/Game.java
+++ b/src/main/java/fr/uca/iut/clfreville2/morpion/game/Game.java
@@ -56,6 +56,9 @@ public class Game {
     }
 
     public MoveResult placeCurrent(Position position) {
+        if (!started) {
+            throw new IllegalStateException();
+        }
         if (board.isOccupied(position)) {
             return new CantPlace();
         }
diff --git a/src/test/java/fr/uca/iut/clfreville2/morpion/game/GameTest.java b/src/test/java/fr/uca/iut/clfreville2/morpion/game/GameTest.java
index b825077..0d4659e 100644
--- a/src/test/java/fr/uca/iut/clfreville2/morpion/game/GameTest.java
+++ b/src/test/java/fr/uca/iut/clfreville2/morpion/game/GameTest.java
@@ -25,6 +25,12 @@ public class GameTest {
         assertThrows(IllegalStateException.class, () -> game.start());
     }
 
+    @Test
+    void cantPlayerIfNotStarted() {
+        Game game = new Game(new Player("Alice"));
+        assertThrows(IllegalStateException.class, () -> game.placeCurrent(new Position(1, 2)));
+    }
+
     @Test
     void getCurrentPlayer() {
         final Player alice = new Player("Alice");
@@ -67,6 +73,7 @@ public class GameTest {
     @Test
     void playerPlace() {
         final Game game = new Game(new Player("Alice"));
+        game.start();
         game.placeCurrent(new Position(1, 2));
         assertEquals(new Placed('x'), game.board().get(new Position(1, 2)));
     }
@@ -74,6 +81,7 @@ public class GameTest {
     @Test
     void playerPlaceDifferentPlayer() {
         final Game game = new Game(new Player("Alice"), new Player("Bob"));
+        game.start();
         game.placeCurrent(new Position(0, 0));
         game.placeCurrent(new Position(2, 2));
         assertEquals(new Placed('o'), game.board().get(new Position(2, 2)));
@@ -82,6 +90,7 @@ public class GameTest {
     @Test
     void workWithThreePlayers() {
         final Game game = new Game(new Player("Albert"), new Player("Blob"), new Player("Cyril"));
+        game.start();
         game.placeCurrent(new Position(1, 2));
         game.placeCurrent(new Position(2, 1));
         game.placeCurrent(new Position(2, 2));
@@ -94,6 +103,7 @@ public class GameTest {
     @ValueSource(ints = {0, 1, 2})
     void scoreVertically(int x) {
         final Game game = new Game(new Player("Ema"));
+        game.start();
         assertEquals(new Result(), game.placeCurrent(new Position(x, 0)));
         assertEquals(new Result(), game.placeCurrent(new Position(x, 1)));
         assertEquals(new Result(new Win(
@@ -106,6 +116,7 @@ public class GameTest {
     @Test
     void scoreDiagonally() {
         final Game game = new Game(new Player("Victor"));
+        game.start();
         assertEquals(new Result(), game.placeCurrent(new Position(0, 0)));
         assertEquals(new Result(), game.placeCurrent(new Position(2, 2)));
         assertEquals(new Result(new Win(
@@ -121,6 +132,7 @@ public class GameTest {
         final Player alice = new Player("Alice");
         final Player bob = new Player("Bob");
         final Game game = new Game(alice, bob);
+        game.start();
         if (secondPlayerWin) {
             game.placeCurrent(new Position(2, 1));
         }
@@ -149,6 +161,7 @@ public class GameTest {
     @Test
     void cantPlaceTwoTimes() {
         final Game game = new Game(new Player("Alice"), new Player("Bob"));
+        game.start();
         game.placeCurrent(new Position(0, 0));
         assertEquals(new CantPlace(), game.placeCurrent(new Position(0, 0)));
     }