diff --git a/README.md b/README.md
index d3e0fae..0412ed4 100644
--- a/README.md
+++ b/README.md
@@ -25,3 +25,5 @@ cargo build
 **Down arrow:** soft drop
 
 **Space bar:** hard drop
+
+**C:** swap piece
diff --git a/TODO.md b/TODO.md
new file mode 100644
index 0000000..da1a381
--- /dev/null
+++ b/TODO.md
@@ -0,0 +1,8 @@
+# TODO
+
+- Lose condition
+- Speedup
+- GUI
+    - Background
+    - Indicators for next/stored piece
+    - Cleared lines counter
diff --git a/src/debug.rs b/src/debug.rs
index 8eeb9bb..a6dbafd 100644
--- a/src/debug.rs
+++ b/src/debug.rs
@@ -13,9 +13,9 @@ impl Plugin for DebugPlugin {
         app.configure_sets(PostUpdate, DebugSet.run_if(is_debug_enabled));
         app.configure_sets(Last, DebugSet.run_if(is_debug_enabled));
 
-        app.insert_resource(DebugMode::on())
+        app.insert_resource(DebugMode::off())
             .add_plugins((
-                // // WorldInspector requires EguiPlugin plugin to be added before it
+                // WorldInspector requires EguiPlugin plugin to be added before it
                 bevy_egui::EguiPlugin::default(),
                 bevy_inspector_egui::quick::WorldInspectorPlugin::new().run_if(is_debug_enabled),
             ))
diff --git a/src/game.rs b/src/game.rs
index c412392..9a7570d 100644
--- a/src/game.rs
+++ b/src/game.rs
@@ -16,13 +16,18 @@ pub fn init(app: &mut App) {
     ));
 
     app.add_event::<tetris::OnPiecePlaced>()
+        .add_event::<tetris::OnLinesCleared>()
+        .add_event::<tetris::OnStoredPieceChanged>()
+        .add_event::<tetris::OnNextPieceChanged>()
         .register_type::<tetris::GameArea>()
+        .register_type::<tetris::GameStats>()
         .register_type::<tetris::GameGravity>()
         .register_type::<tetris::BlockSet>()
         .register_type::<tetris::NextPiece>()
         .register_type::<tetris::Piece>()
         .register_type::<tetris::PieceControls>()
         .register_type::<tetris::ControllablePiece>()
+        .register_type::<tetris::SwappedPiece>()
         .register_type::<tetris::Gravity>()
         .register_type::<tetris::Block>()
         .register_type::<prefab::PieceType>()
@@ -30,6 +35,15 @@ pub fn init(app: &mut App) {
         .register_type::<grid::GridTransform>()
         .add_systems(Startup, systems::setup_game_scene)
         .add_systems(PreUpdate, (systems::repeat_inputs, systems::apply_gravity))
-        .add_systems(Update, (systems::demo_2d, systems::apply_piece_movement))
+        .add_systems(
+            Update,
+            (
+                systems::demo_2d,
+                systems::store_piece,
+                systems::apply_piece_movement,
+                systems::trigger_on_next_piece_changed,
+                systems::trigger_on_stored_piece_changed,
+            ),
+        )
         .add_systems(PostUpdate, systems::grid_positioning);
 }
diff --git a/src/game/prefab.rs b/src/game/prefab.rs
index 7a7b53e..a47b607 100644
--- a/src/game/prefab.rs
+++ b/src/game/prefab.rs
@@ -65,7 +65,7 @@ impl PieceType {
             Self::J => [(-1, 0), (-1, 1), (0, 0), (1, 0)],
             Self::S => [(-1, 0), (0, 0), (0, 1), (1, 1)],
             Self::Z => [(-1, 1), (0, 0), (0, 1), (1, 0)],
-            Self::Square => [(0, 0), (0, 1), (1, 0), (1, 1)],
+            Self::Square => [(-1, 0), (-1, 1), (0, 0), (0, 1)],
         }
         .map(|pos| pos.into())
     }
diff --git a/src/game/systems.rs b/src/game/systems.rs
index f93944a..5f9a243 100644
--- a/src/game/systems.rs
+++ b/src/game/systems.rs
@@ -3,9 +3,11 @@ mod game_scene;
 mod grid;
 mod input;
 mod movement;
+mod ui;
 
 pub use demo::*;
 pub use game_scene::*;
 pub use grid::*;
 pub use input::*;
 pub use movement::*;
+pub use ui::*;
diff --git a/src/game/systems/game_scene.rs b/src/game/systems/game_scene.rs
index 284c96f..796aba5 100644
--- a/src/game/systems/game_scene.rs
+++ b/src/game/systems/game_scene.rs
@@ -8,30 +8,131 @@ pub fn setup_game_scene(world: &mut World) {
     let game_area = GameArea::default();
     let mut next_piece = NextPiece::default();
     let starting_piece = next_piece.take_and_generate();
-    world
-        .spawn((
-            Name::from("Game scene"),
-            GameGravity::default(),
-            game_area.clone(),
-            next_piece,
-            children![
-                (Transform::from_xyz(-16.0, 88.0, 10.0), DemoCamera2d,),
-                // Create first piece
-                (
-                    GridTransform {
-                        translation: game_area.block_spawn_point()
-                    },
-                    ControllablePiece,
-                    create_piece(starting_piece),
-                ),
-            ],
-        ))
+
+    let mut game_entity = world.spawn((
+        Name::from("Game scene"),
+        GameGravity::default(),
+        GameStats::default(),
+        game_area.clone(),
+        next_piece,
+        children![
+            (Transform::from_xyz(36.0, 88.0, 10.0), DemoCamera2d,),
+            // Create first piece
+            (
+                GridTransform {
+                    translation: game_area.block_spawn_point()
+                },
+                ControllablePiece,
+                create_piece(starting_piece),
+            ),
+        ],
+    ));
+
+    game_entity
         .observe(handle_placed_piece)
         .observe(handle_line_clear);
+
+    // Next piece indicator
+    game_entity.with_child((
+        Name::from("Next piece indicator"),
+        Grid::default(),
+        GridTransform::from_xy(13, 18),
+        Observer::new(update_next_piece_ui).with_entity(game_entity.id()),
+    ));
+
+    // Stored piece indicator
+    game_entity.with_child((
+        Name::from("Stored piece indicator"),
+        Grid::default(),
+        GridTransform::from_xy(-4, 18),
+        Observer::new(update_stored_piece_ui).with_entity(game_entity.id()),
+    ));
+
     world.flush();
 }
 
-pub fn handle_placed_piece(trigger: Trigger<OnPiecePlaced>, world: &mut World) {
+pub fn store_piece(
+    mut commands: Commands,
+    piece_query: Query<(Entity, &PieceControls, &PieceType, &ChildOf), Without<SwappedPiece>>,
+    mut store_query: Query<(Option<&mut StoredPiece>, &GameArea)>,
+    mut next_piece_query: Query<&mut NextPiece>,
+) {
+    for (old_entity, controls, piece, parent) in piece_query.iter() {
+        if controls.store
+            && let Ok((maybes_stored_piece, game_area)) = store_query.get_mut(parent.parent())
+        {
+            let mut game = commands.entity(parent.parent());
+            match maybes_stored_piece {
+                Some(mut stored_piece) => {
+                    game.with_child((
+                        GridTransform {
+                            translation: game_area.block_spawn_point(),
+                        },
+                        ControllablePiece,
+                        SwappedPiece,
+                        create_piece(stored_piece.piece),
+                    ));
+                    stored_piece.piece = *piece;
+                    commands.entity(old_entity).despawn();
+                }
+                None => {
+                    if let Ok(mut next_piece) = next_piece_query.get_mut(parent.parent()) {
+                        game.insert(StoredPiece { piece: *piece });
+                        game.with_child((
+                            GridTransform {
+                                translation: game_area.block_spawn_point(),
+                            },
+                            ControllablePiece,
+                            SwappedPiece,
+                            create_piece(next_piece.take_and_generate()),
+                        ));
+                        commands.entity(old_entity).despawn();
+                    }
+                }
+            }
+        }
+    }
+}
+
+fn update_next_piece_ui(
+    trigger: Trigger<OnNextPieceChanged>,
+    mut commands: Commands,
+    parent_query: Query<&ChildOf>,
+    next_piece_query: Query<&NextPiece>,
+) {
+    if let Ok(mut indicator) = commands.get_entity(trigger.observer()) {
+        // Despawn children recursively
+        indicator.despawn_related::<Children>();
+
+        if let Ok(next_piece) = parent_query
+            .get(indicator.id())
+            .and_then(|p| next_piece_query.get(p.parent()))
+        {
+            indicator.with_child((Grid::default(), create_piece(next_piece.piece)));
+        }
+    }
+}
+
+fn update_stored_piece_ui(
+    trigger: Trigger<OnStoredPieceChanged>,
+    mut commands: Commands,
+    parent_query: Query<&ChildOf>,
+    stored_piece_query: Query<&StoredPiece>,
+) {
+    if let Ok(mut indicator) = commands.get_entity(trigger.observer()) {
+        // Despawn children recursively
+        indicator.despawn_related::<Children>();
+
+        if let Ok(stored_piece) = parent_query
+            .get(indicator.id())
+            .and_then(|p| stored_piece_query.get(p.parent()))
+        {
+            indicator.with_child((Grid::default(), create_piece(stored_piece.piece)));
+        }
+    }
+}
+
+fn handle_placed_piece(trigger: Trigger<OnPiecePlaced>, world: &mut World) {
     let game_area = trigger.target();
     let event = *trigger.event();
 
@@ -65,8 +166,6 @@ pub fn handle_placed_piece(trigger: Trigger<OnPiecePlaced>, world: &mut World) {
         .run_system_cached_with(create_next_piece, game_area)
         .expect("Creating new piece");
     world.flush();
-
-    // TODO: Lose condition
 }
 
 fn rebuild_collisions(
@@ -155,7 +254,7 @@ fn check_full_rows(
     cleared_rows
 }
 
-fn check_lose_condition(In(game_area_entity): In<Entity>) {}
+fn check_lose_condition(In(_game_area_entity): In<Entity>) {}
 
 fn create_next_piece(
     In(game_area_entity): In<Entity>,
@@ -174,13 +273,13 @@ fn create_next_piece(
 
 fn handle_line_clear(
     trigger: Trigger<OnLinesCleared>,
-    game_area_query: Query<&Children>,
+    mut game_area_query: Query<(&Children, Option<&mut GameStats>)>,
     mut block_query: Query<(Entity, &mut GridTransform), With<Block>>,
     mut commands: Commands,
 ) {
     let lines = trigger.event().lines.clone();
-    let children = game_area_query
-        .get(trigger.target())
+    let (children, maybe_stats) = game_area_query
+        .get_mut(trigger.target())
         .expect("Getting GameArea component to clear rows");
 
     enum BlockOperation {
@@ -221,4 +320,8 @@ fn handle_line_clear(
             _ => (),
         };
     }
+
+    if let Some(mut stats) = maybe_stats {
+        stats.lines_cleared += lines.len() as i32;
+    }
 }
diff --git a/src/game/systems/input.rs b/src/game/systems/input.rs
index a46285d..b7858f9 100644
--- a/src/game/systems/input.rs
+++ b/src/game/systems/input.rs
@@ -49,5 +49,9 @@ pub fn repeat_inputs(
         if key_input.just_pressed(KeyCode::Space) {
             controls.instant_drop = true;
         }
+
+        if key_input.just_pressed(KeyCode::KeyC) {
+            controls.store = true;
+        }
     }
 }
diff --git a/src/game/systems/ui.rs b/src/game/systems/ui.rs
new file mode 100644
index 0000000..d3d43bd
--- /dev/null
+++ b/src/game/systems/ui.rs
@@ -0,0 +1,31 @@
+use bevy::prelude::*;
+
+use crate::game::tetris::*;
+
+pub fn trigger_on_next_piece_changed(
+    mut commands: Commands,
+    next_piece_query: Query<(Entity, &NextPiece), Changed<NextPiece>>,
+) {
+    for (entity, changed) in next_piece_query.iter() {
+        commands.trigger_targets(
+            OnNextPieceChanged {
+                piece: changed.piece,
+            },
+            entity,
+        );
+    }
+}
+
+pub fn trigger_on_stored_piece_changed(
+    mut commands: Commands,
+    next_piece_query: Query<(Entity, &StoredPiece), Changed<StoredPiece>>,
+) {
+    for (entity, changed) in next_piece_query.iter() {
+        commands.trigger_targets(
+            OnStoredPieceChanged {
+                piece: changed.piece,
+            },
+            entity,
+        );
+    }
+}
diff --git a/src/game/tetris.rs b/src/game/tetris.rs
index 80d62ca..06e72df 100644
--- a/src/game/tetris.rs
+++ b/src/game/tetris.rs
@@ -11,32 +11,9 @@ pub mod input;
 pub type YPos = i32;
 pub type XPos = i32;
 
-#[derive(Component, Debug, Default, Reflect)]
-#[reflect(Component)]
-pub struct BlockSet {
-    blocks: HashSet<Vector2I>,
-}
-
-impl BlockSet {
-    pub fn new(blocks: HashSet<Vector2I>) -> Self {
-        Self { blocks }
-    }
-
-    pub fn cast_point(&self, pos: &Vector2I) -> bool {
-        self.blocks.contains(pos)
-    }
-
-    pub fn cast_shape(&self, shape_pos: Vector2I, local_blocks: &[Vector2I]) -> bool {
-        local_blocks
-            .iter()
-            .map(|local_pos| shape_pos + *local_pos)
-            .any(|global_pos| self.cast_point(&global_pos))
-    }
-}
-
 #[derive(Component, Clone, Debug, Reflect)]
 #[reflect(Component)]
-#[require(Grid, NextPiece, BlockSet)]
+#[require(Grid, NextPiece, BlockSet, GameStats)]
 pub struct GameArea {
     pub bottom_boundary: i32,
     pub kill_height: i32,
@@ -90,6 +67,35 @@ impl GameArea {
     }
 }
 
+#[derive(Component, Debug, Default, Reflect)]
+#[reflect(Component)]
+pub struct GameStats {
+    pub lines_cleared: i32,
+}
+
+#[derive(Component, Debug, Default, Reflect)]
+#[reflect(Component)]
+pub struct BlockSet {
+    blocks: HashSet<Vector2I>,
+}
+
+impl BlockSet {
+    pub fn new(blocks: HashSet<Vector2I>) -> Self {
+        Self { blocks }
+    }
+
+    pub fn cast_point(&self, pos: &Vector2I) -> bool {
+        self.blocks.contains(pos)
+    }
+
+    pub fn cast_shape(&self, shape_pos: Vector2I, local_blocks: &[Vector2I]) -> bool {
+        local_blocks
+            .iter()
+            .map(|local_pos| shape_pos + *local_pos)
+            .any(|global_pos| self.cast_point(&global_pos))
+    }
+}
+
 #[derive(Component, Debug, Reflect)]
 #[reflect(Component)]
 pub struct GameGravity {
@@ -122,6 +128,7 @@ pub struct PieceControls {
     pub fast_drop: bool,
     pub movement: Option<input::Move>,
     pub rotation: Option<input::Rotation>,
+    pub store: bool,
 }
 
 #[derive(Component, Debug, Reflect)]
@@ -129,12 +136,23 @@ pub struct PieceControls {
 #[require(PieceControls)]
 pub struct ControllablePiece;
 
+/// Indicates that the piece was already swapped, so it can't be swapped again.
+#[derive(Component, Debug, Reflect)]
+#[reflect(Component)]
+pub struct SwappedPiece;
+
 #[derive(Component, Clone, Debug, Reflect)]
 #[reflect(Component)]
 pub struct NextPiece {
     pub piece: PieceType,
 }
 
+#[derive(Component, Clone, Debug, Reflect)]
+#[reflect(Component)]
+pub struct StoredPiece {
+    pub piece: PieceType,
+}
+
 impl Default for NextPiece {
     fn default() -> Self {
         Self {
@@ -168,3 +186,13 @@ pub struct OnPiecePlaced {
 pub struct OnLinesCleared {
     pub lines: Vec<YPos>,
 }
+
+#[derive(Event, Clone, Debug)]
+pub struct OnNextPieceChanged {
+    pub piece: PieceType,
+}
+
+#[derive(Event, Clone, Debug)]
+pub struct OnStoredPieceChanged {
+    pub piece: PieceType,
+}