diff --git a/src/board.rs b/src/board.rs
index fa92d8b..56dd2d2 100644
--- a/src/board.rs
+++ b/src/board.rs
@@ -81,6 +81,24 @@ impl BoardSlot {
 
         Ok(mesh)
     }
+
+    pub fn valid(&self) -> bool {
+        self.state != BoardSlotState::Invalid
+    }
+
+    pub fn white(&self) -> bool {
+        match self.state {
+            BoardSlotState::White(_) => true,
+            _ => false,
+        }
+    }
+
+    pub fn black(&self) -> bool {
+        match self.state {
+            BoardSlotState::Black(_) => true,
+            _ => false,
+        }
+    }
 }
 
 #[derive(Debug, PartialEq, Eq, Clone, Copy)]
diff --git a/src/game.rs b/src/game.rs
index b5a4e34..b4b307f 100644
--- a/src/game.rs
+++ b/src/game.rs
@@ -1,6 +1,6 @@
 use std::sync::{
     atomic::{AtomicU32, Ordering::SeqCst},
-    Arc, Mutex,
+    Arc, Mutex, MutexGuard,
 };
 
 use anyhow::Result;
@@ -28,6 +28,7 @@ pub struct Stone {
 #[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Clone, Copy)]
 pub enum GameState {
     Placing,
+    Removing,
     Main,
 }
 
@@ -37,11 +38,26 @@ pub enum PlayerColor {
     Black,
 }
 
+#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Clone, Copy)]
+pub enum MillState {
+    White,
+    Black,
+    None,
+}
+
 impl PlayerColor {
     pub fn swap(&mut self) {
         *self = match *self {
-            PlayerColor::White => PlayerColor::Black,
-            PlayerColor::Black => PlayerColor::White,
+            PlayerColor::White => {
+                MillGame::log("swapped to black player");
+
+                PlayerColor::Black
+            }
+            PlayerColor::Black => {
+                MillGame::log("swapped to white player");
+
+                PlayerColor::White
+            }
         }
     }
 }
@@ -196,8 +212,10 @@ impl MillGame {
                 }
 
                 if let Some(me) = weak_self.upgrade() {
+                    Self::log("start game");
+
                     *me.state.lock().unwrap() = GameState::Placing;
-                    *me.current_player.lock().unwrap() = PlayerColor::White;
+                    *me.current_player.lock().unwrap() = PlayerColor::Black;
 
                     me.next_game_step()?;
                 }
@@ -210,22 +228,13 @@ impl MillGame {
     }
 
     fn next_game_step(&self) -> Result<()> {
-        match *self.current_player.lock().unwrap() {
-            PlayerColor::White => {
-                self.black_player_label
-                    .set_background(Color::try_from("#9b9292")?)?;
-                self.white_player_label.set_background(Color::Yellow)?;
-            }
-            PlayerColor::Black => {
-                self.white_player_label
-                    .set_background(Color::try_from("#9b9292")?)?;
-                self.black_player_label.set_background(Color::Yellow)?;
-            }
-        }
+        Self::log("next_game_step");
 
         {
             let mut state = self.state.lock().unwrap();
 
+            Self::log(&format!("\tstate: {:?}", state));
+
             match *state {
                 GameState::Placing => {
                     if !self
@@ -241,34 +250,91 @@ impl MillGame {
                             .iter()
                             .any(|stones| stones.state == StoneState::ReadyToBePlaced)
                     {
+                        Self::log("change state to Main");
                         *state = GameState::Main;
                     }
+
+                    if self.check_for_mill() != MillState::None {
+                        Self::log("change state to Removing");
+                        *state = GameState::Removing;
+                    } else {
+                        self.current_player.lock().unwrap().swap();
+                    }
+                }
+                GameState::Removing => {
+                    if !self
+                        .black_stones
+                        .lock()
+                        .unwrap()
+                        .iter()
+                        .any(|stones| stones.state == StoneState::ReadyToBePlaced)
+                        && !self
+                            .white_stones
+                            .lock()
+                            .unwrap()
+                            .iter()
+                            .any(|stones| stones.state == StoneState::ReadyToBePlaced)
+                    {
+                        Self::log("change state to Main");
+                        *state = GameState::Main;
+                    } else {
+                        Self::log("change state to Placing");
+                        *state = GameState::Placing;
+                    }
+
+                    self.current_player.lock().unwrap().swap();
+                }
+                GameState::Main => {
+                    if self.check_for_mill() != MillState::None {
+                        Self::log("change state to Removing");
+                        *state = GameState::Removing;
+                    } else {
+                        self.current_player.lock().unwrap().swap();
+                    }
                 }
-                GameState::Main => {}
             }
         }
 
-        if *self.current_player.lock().unwrap() == self.simple_ai.player_color {
-            match self.simple_ai.player_color {
-                PlayerColor::White => self.simple_ai.step(
-                    &mut *self.white_stones.lock().unwrap(),
-                    self.board.lock().unwrap().slots(),
-                    &mut *self.scene.lock().unwrap(),
-                )?,
-                PlayerColor::Black => self.simple_ai.step(
-                    &mut *self.black_stones.lock().unwrap(),
-                    self.board.lock().unwrap().slots(),
-                    &mut *self.scene.lock().unwrap(),
-                )?,
-            }
+        let player = *self.current_player.lock().unwrap();
+
+        Self::log(&format!("current player {:?}", player));
+
+        match player {
+            PlayerColor::White => {
+                self.black_player_label
+                    .set_background(Color::try_from("#9b9292")?)?;
+                self.white_player_label.set_background(Color::Yellow)?;
+            }
+            PlayerColor::Black => {
+                self.white_player_label
+                    .set_background(Color::try_from("#9b9292")?)?;
+                self.black_player_label.set_background(Color::Yellow)?;
+            }
+        }
+
+        if player == self.simple_ai.player_color {
+            Self::log("current player is AI");
+
+            self.simple_ai.step(
+                &mut self.stones(self.simple_ai.player_color),
+                self.board.lock().unwrap().slots(),
+                &mut *self.scene.lock().unwrap(),
+                *self.state.lock().unwrap(),
+            )?;
 
-            self.current_player.lock().unwrap().swap();
             self.next_game_step()?;
         }
 
         Ok(())
     }
 
+    fn stones(&self, player_color: PlayerColor) -> MutexGuard<'_, [Stone; 9]> {
+        match player_color {
+            PlayerColor::White => self.white_stones.lock().unwrap(),
+            PlayerColor::Black => self.black_stones.lock().unwrap(),
+        }
+    }
+
     fn init_nine_stones(engine: &Arc<Engine>, color: Color) -> Result<[EntityObject; 9]> {
         Ok((0..9)
             .map(|_| Self::init_stone(engine, color))
@@ -327,9 +393,19 @@ impl MillGame {
         player_color: PlayerColor,
         scene: &mut Scene,
     ) -> Result<()> {
+        Self::log("place_stone");
+
         match player_color {
-            PlayerColor::White => slot.state = BoardSlotState::White(stone.stone),
-            PlayerColor::Black => slot.state = BoardSlotState::Black(stone.stone),
+            PlayerColor::White => {
+                Self::log(&format!("place white stone"));
+
+                slot.state = BoardSlotState::White(stone.stone);
+            }
+            PlayerColor::Black => {
+                Self::log(&format!("place black stone"));
+
+                slot.state = BoardSlotState::Black(stone.stone);
+            }
         }
 
         stone.state = StoneState::Placed;
@@ -342,16 +418,115 @@ impl MillGame {
         Ok(())
     }
 
-    pub fn check_for_mill(&self) -> Result<bool> {
-        let slots = self.board.lock().unwrap().slots();
+    pub fn remove_stone(slot: &mut BoardSlot, scene: &mut Scene) -> Result<()> {
+        Self::log("remove_stone");
+
+        let entity = match slot.state {
+            BoardSlotState::Black(e) => {
+                Self::log(&format!("\tremove black stone"));
+
+                e
+            }
+            BoardSlotState::White(e) => {
+                Self::log(&format!("\tremove white stone"));
+
+                e
+            }
+            _ => unreachable!(),
+        };
+
+        scene.remove_entity(entity)?;
+
+        slot.state = BoardSlotState::Empty;
+
+        Ok(())
+    }
+
+    fn check_mill(s1: &BoardSlot, s2: &BoardSlot, s3: &BoardSlot) -> MillState {
+        if s1.valid() && s2.valid() && s3.valid() {
+            if s1.white() && s2.white() && s3.white() {
+                return MillState::White;
+            } else if s1.black() && s2.black() && s3.black() {
+                return MillState::Black;
+            }
+        }
+
+        MillState::None
+    }
+
+    pub fn check_for_mill(&self) -> MillState {
+        Self::log("check for mill");
+
+        let mut board = self.board.lock().unwrap();
+        let slots = board.slots();
 
         for x in 0..3 {
             for y in 0..3 {
-                for z in 0..3 {
-                    //
+                let state = Self::check_mill(&slots[x][y][0], &slots[x][y][1], &slots[x][y][2]);
+
+                if state != MillState::None {
+                    Self::log(&format!("mill found {:?}", state));
+
+                    return state;
                 }
             }
         }
+
+        for x in 0..3 {
+            for z in 0..3 {
+                let state = Self::check_mill(&slots[x][0][z], &slots[x][1][z], &slots[x][2][z]);
+
+                if state != MillState::None {
+                    Self::log(&format!("mill found {:?}", state));
+
+                    return state;
+                }
+            }
+        }
+
+        for y in 0..3 {
+            for z in 0..3 {
+                let state = Self::check_mill(&slots[0][y][z], &slots[1][y][z], &slots[2][y][z]);
+
+                if state != MillState::None {
+                    Self::log(&format!("mill found {:?}", state));
+
+                    return state;
+                }
+            }
+        }
+
+        MillState::None
+    }
+
+    fn check_mouse_click<F>(&self, f: F) -> Result<()>
+    where
+        F: FnOnce(&Self, &mut BoardSlot, &mut Scene) -> Result<()>,
+    {
+        Self::log("check_mouse_click");
+
+        self.scene.lock().unwrap().on_scene(|scene| {
+            if let Some(world_space) =
+                scene.screen_space_to_world(self.mouse_x.load(SeqCst), self.mouse_y.load(SeqCst))?
+            {
+                if let Some(slot) = self
+                    .board
+                    .lock()
+                    .unwrap()
+                    .close_to_marker(world_space.truncate())
+                {
+                    Self::log("click is close to marker");
+
+                    f(self, slot, scene)?;
+                }
+            }
+
+            Ok(())
+        })
+    }
+
+    pub fn log(s: &str) {
+        println!("{}", s);
     }
 }
 
@@ -378,39 +553,60 @@ impl EngineObject for MillGame {
             }
             EngineEvent::MouseButtonDown(button) => match button {
                 MouseButton::Left => {
-                    let mut placed = false;
+                    let state = *self.state.lock().unwrap();
+                    Self::log(&format!("User click at state {:?}", state));
+
+                    match state {
+                        GameState::Placing => {
+                            let mut placed = false;
+
+                            self.check_mouse_click(|me, slot, scene| {
+                                let current_player = *self.current_player.lock().unwrap();
 
-                    self.scene.lock().unwrap().on_scene(|scene| {
-                        if let Some(world_space) = scene.screen_space_to_world(
-                            self.mouse_x.load(SeqCst),
-                            self.mouse_y.load(SeqCst),
-                        )? {
-                            if let Some(slot) = self
-                                .board
-                                .lock()
-                                .unwrap()
-                                .close_to_marker(world_space.truncate())
-                            {
                                 if let Some(placable) = self
-                                    .black_stones
-                                    .lock()
-                                    .unwrap()
+                                    .stones(current_player)
                                     .iter_mut()
                                     .find(|stone| stone.state == StoneState::ReadyToBePlaced)
                                 {
-                                    Self::place_stone(placable, slot, PlayerColor::Black, scene)?;
+                                    Self::place_stone(placable, slot, current_player, scene)?;
 
                                     placed = true;
                                 }
+
+                                Ok(())
+                            })?;
+
+                            if placed {
+                                self.next_game_step()?;
                             }
                         }
+                        GameState::Removing => {
+                            let mut removed = false;
 
-                        Ok(())
-                    })?;
+                            self.check_mouse_click(|me, slot, scene| {
+                                Self::log(&format!(
+                                    "state {:?} - player {:?}",
+                                    slot.state,
+                                    *self.current_player.lock().unwrap()
+                                ));
 
-                    if placed {
-                        self.current_player.lock().unwrap().swap();
-                        self.next_game_step()?;
+                                if match (slot.state, *self.current_player.lock().unwrap()) {
+                                    (BoardSlotState::Black(_), PlayerColor::White) => true,
+                                    (BoardSlotState::White(_), PlayerColor::Black) => true,
+                                    _ => false,
+                                } {
+                                    removed = true;
+                                    Self::remove_stone(slot, scene)?;
+                                }
+
+                                Ok(())
+                            })?;
+
+                            if removed {
+                                self.next_game_step()?;
+                            }
+                        }
+                        GameState::Main => todo!(),
                     }
                 }
                 MouseButton::Middle => self.camera_controls.lock().unwrap().hold(),
diff --git a/src/simple_ai.rs b/src/simple_ai.rs
index 9508ff7..b2e9935 100644
--- a/src/simple_ai.rs
+++ b/src/simple_ai.rs
@@ -1,6 +1,6 @@
 use crate::{
     board::{BoardSlot, BoardSlotState},
-    game::{MillGame, PlayerColor, Stone, StoneState},
+    game::{GameState, MillGame, PlayerColor, Stone, StoneState},
 };
 
 use anyhow::Result;
@@ -20,29 +20,61 @@ impl SimpleAI {
         stones: &mut [Stone; 9],
         board: &mut [[[BoardSlot; 3]; 3]; 3],
         scene: &mut SceneHandle,
+        state: GameState,
     ) -> Result<()> {
-        if let Some(placable) = stones
-            .iter_mut()
-            .find(|stone| stone.state == StoneState::ReadyToBePlaced)
-        {
-            let mut free_slots: Vec<&mut BoardSlot> = board
-                .iter_mut()
-                .flatten()
-                .flatten()
-                .filter(|slot| slot.state == BoardSlotState::Empty)
-                .collect();
+        MillGame::log(&format!("AI at state {:?}", state));
 
-            let len = free_slots.len();
+        match state {
+            GameState::Placing => {
+                if let Some(placable) = stones
+                    .iter_mut()
+                    .find(|stone| stone.state == StoneState::ReadyToBePlaced)
+                {
+                    let mut free_slots: Vec<&mut BoardSlot> = board
+                        .iter_mut()
+                        .flatten()
+                        .flatten()
+                        .filter(|slot| slot.state == BoardSlotState::Empty)
+                        .collect();
 
-            let slot = &mut free_slots[Random::range(0, len as u32) as usize];
+                    let len = free_slots.len();
 
-            scene.on_scene(|scene| {
-                MillGame::place_stone(placable, slot, self.player_color, scene)?;
+                    let slot = &mut free_slots[Random::range(0, len as u32) as usize];
 
-                Ok(())
-            })?;
+                    scene.on_scene(|scene| {
+                        MillGame::place_stone(placable, slot, self.player_color, scene)?;
+
+                        Ok(())
+                    })?;
+                }
+            }
+            GameState::Removing => {
+                let mut other_color: Vec<&mut BoardSlot> = board
+                    .iter_mut()
+                    .flatten()
+                    .flatten()
+                    .filter(|slot| match (slot.state, self.player_color) {
+                        (BoardSlotState::Black(_), PlayerColor::White) => true,
+                        (BoardSlotState::White(_), PlayerColor::Black) => true,
+                        _ => false,
+                    })
+                    .collect();
+
+                let len = other_color.len();
+
+                let slot = &mut other_color[Random::range(0, len as u32) as usize];
+
+                scene.on_scene(|scene| {
+                    MillGame::remove_stone(slot, scene)?;
+
+                    Ok(())
+                })?;
+            }
+            GameState::Main => todo!(),
         }
 
+        MillGame::log("finish AI");
+
         Ok(())
     }
 }