diff --git a/CMakeLists.txt b/CMakeLists.txt
new file mode 100644
index 0000000..54c7f64
--- /dev/null
+++ b/CMakeLists.txt
@@ -0,0 +1,90 @@
+cmake_minimum_required(VERSION 3.20)
+project(PathfindingDemo)
+
+set(CMAKE_CXX_STANDARD 23)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
+# Find required packages
+find_package(PkgConfig REQUIRED)
+pkg_check_modules(SDL3 REQUIRED sdl3)
+pkg_check_modules(SDL3_image REQUIRED sdl3-image)
+find_package(OpenGL REQUIRED)
+find_package(GLEW REQUIRED)
+
+# Add Google Test
+find_package(GTest REQUIRED)
+
+# Include directories
+include_directories(cpp/src)
+
+# Source files for the main executable
+set(MAIN_SOURCES
+    cpp/src/main.cpp
+    cpp/src/camera.cpp
+    cpp/src/entities.cpp
+    cpp/src/gameloop.cpp
+    cpp/src/map.cpp
+    cpp/src/pathfinder/base.cpp
+    cpp/src/pathfinder/bfs.cpp
+    cpp/src/pathfinder/dijkstra.cpp
+    cpp/src/pathfinder/gbfs.cpp
+    cpp/src/pathfinder/utils.cpp
+    cpp/src/pathfindingdemo.cpp
+    cpp/src/sprite.cpp
+    cpp/src/tile.cpp
+    cpp/src/user_input.cpp
+    cpp/src/window.cpp
+)
+
+# Header files (for IDE support)
+set(HEADERS
+    cpp/src/array.hpp
+    cpp/src/camera.hpp
+    cpp/src/entities.hpp
+    cpp/src/gameloop.hpp
+    cpp/src/log.hpp
+    cpp/src/map.hpp
+    cpp/src/math.hpp
+    cpp/src/pathfinder/base.hpp
+    cpp/src/pathfinder/bfs.hpp
+    cpp/src/pathfinder/dijkstra.hpp
+    cpp/src/pathfinder/gbfs.hpp
+    cpp/src/pathfinder/utils.hpp
+    cpp/src/pathfindingdemo.hpp
+    cpp/src/sprite.hpp
+    cpp/src/tile.hpp
+    cpp/src/user_input.hpp
+    cpp/src/window.hpp
+)
+
+# Create main executable
+add_executable(pathfinding_demo ${MAIN_SOURCES} ${HEADERS})
+
+# Link libraries for main executable
+target_link_libraries(pathfinding_demo 
+    ${SDL3_LIBRARIES} 
+    ${SDL3_image_LIBRARIES}
+    OpenGL::GL
+    GLEW::GLEW
+)
+
+# Add compile flags
+target_compile_options(pathfinding_demo PRIVATE ${SDL3_CFLAGS_OTHER})
+
+# Test executable
+add_executable(tests cpp/test/test.cpp)
+target_link_libraries(tests GTest::gtest GTest::gtest_main)
+
+# Enable testing
+enable_testing()
+add_test(NAME unit_tests COMMAND tests)
+
+# Compiler-specific options
+if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU" OR CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+    target_compile_options(pathfinding_demo PRIVATE -Wall -Wextra -Wpedantic)
+    target_compile_options(tests PRIVATE -Wall -Wextra -Wpedantic)
+endif()
+
+# Debug/Release configurations
+set(CMAKE_CXX_FLAGS_DEBUG "-g -O0")
+set(CMAKE_CXX_FLAGS_RELEASE "-O3 -DNDEBUG")
diff --git a/cpp/src/camera.hpp b/cpp/src/camera.hpp
index f57b441..b321baa 100644
--- a/cpp/src/camera.hpp
+++ b/cpp/src/camera.hpp
@@ -15,6 +15,18 @@ public:
   WorldPos   WindowToWorld(WindowPos)      const;
   WindowSize WorldToWindowSize(WorldSize)  const;
   WorldSize  WindowToWorldSize(WindowSize) const;
+  
+  template <typename T>
+  requires std::floating_point<T>
+  T WindowToWorldSize(T window_size) const {
+    return window_size / static_cast<T>(m_Zoom);
+  }
+  
+  template <typename T>
+  requires std::floating_point<T>
+  T WorldToWindowSize(T world_size) const {
+    return world_size * static_cast<T>(m_Zoom);
+  }
 
 private:
   // TODO this should be replaced with a matrix
diff --git a/cpp/src/entities.cpp b/cpp/src/entities.cpp
index d8e1ad2..453b003 100644
--- a/cpp/src/entities.cpp
+++ b/cpp/src/entities.cpp
@@ -46,6 +46,47 @@ void Entity::Update(float time_delta) {
   m_Position += m_ActualVelocity * time_delta;
 }
 
+std::optional<WorldPos> Entity::GetMoveTarget()
+{
+  auto& path = GetPath();
+  if (path.empty()) {
+    return {};
+  }
+
+  WorldPos current_pos = GetPosition();
+  WorldPos next_pos = path.front();
+
+  if (current_pos.DistanceTo(next_pos) > 1.0) {
+    // target not reached yet
+    return next_pos;
+  }
+  // target reached, pop it
+  //m_MoveQueue.pop();
+  path.erase(path.begin());
+  // return nothing - if there's next point in the queue,
+  // we'll get it in the next iteration
+  return {};
+}
+
+bool Entity::CollidesWith(const Entity& other) const
+{
+  const auto& A = *this;
+  const auto& B = other;
+
+  auto position_A = A.GetPosition();
+  auto position_B = B.GetPosition();
+  auto distance_sq = position_A.DistanceSquared(position_B);
+  auto collision_distance_sq =
+      A.GetCollisionRadiusSquared() +
+      B.GetCollisionRadiusSquared() +
+      2 * A.GetCollisionRadius() * B.GetCollisionRadius();
+  if (distance_sq < collision_distance_sq)
+  {
+    return true;
+  }
+  return false;
+}
+
 Player::Player() {
   LOG_DEBUG(".");
   if (m_Sprite == nullptr) {
diff --git a/cpp/src/entities.hpp b/cpp/src/entities.hpp
index bed7204..6ad8521 100644
--- a/cpp/src/entities.hpp
+++ b/cpp/src/entities.hpp
@@ -5,10 +5,12 @@
 #include <iostream>
 #include <memory>
 #include <string_view>
+#include <optional>
 
 #include "log.hpp"
 #include "math.hpp"
 #include "sprite.hpp"
+#include "pathfinder/base.hpp"
 
 class Entity {
 public:
@@ -56,14 +58,29 @@ public:
 
   void ZeroActualVelocityInDirection(WorldPos direction);
 
+  const pathfinder::Path& GetPath() const { return m_Path; }
+  pathfinder::Path& GetPath() { return m_Path; }
+  void SetPath(pathfinder::Path& path) { m_Path = path; }
+  std::optional<WorldPos> GetMoveTarget();
+
+  bool CollidesWith(const Entity& other) const;
+
+  bool IsCollisionBoxVisible() const { return m_CollisionBoxVisible; }
+
+  void Select() { m_Selected = true; }
+  void Deselect() { m_Selected = false; }
+  bool IsSelected() const { return m_Selected; }
+
 protected:
   WorldPos m_Position;
   WorldPos m_ActualVelocity;
   WorldPos m_RequestedVelocity;
+  pathfinder::Path m_Path;
 
 private:
   bool m_FlagExpired = false;
-  static constexpr float m_CollisionRadiusSq = 1000.0f;
+  bool m_CollisionBoxVisible = true;
+  bool m_Selected = false;
 };
 
 class Player final : public Entity {
@@ -75,7 +92,7 @@ public:
   constexpr Entity::Type GetType() const override {
     return Entity::Type::PLAYER;
   }
-  constexpr float GetCollisionRadius() const override { return 50.0f; }
+  constexpr float GetCollisionRadius() const override { return 25.0f; }
   bool IsMovable() const override { return true; }
   bool IsCollidable() const override { return true; }
 
diff --git a/cpp/src/gameloop.cpp b/cpp/src/gameloop.cpp
index 5e35aa4..7944493 100644
--- a/cpp/src/gameloop.cpp
+++ b/cpp/src/gameloop.cpp
@@ -21,26 +21,52 @@ void GameLoop::Draw() {
           TilePos{static_cast<int32_t>(row), static_cast<int32_t>(col)}));
       const auto &size = camera.WorldToWindowSize(map.GetTileSize());
       // LOG_DEBUG("Drawing rect (", row, ", ", col, ")");
-      m_Window->DrawRect(position, size, tiles[row][col]->R, tiles[row][col]->G,
+      m_Window->DrawFilledRect(position, size, tiles[row][col]->R, tiles[row][col]->G,
                          tiles[row][col]->B, tiles[row][col]->A);
     }
   }
 
   // draw the path, if it exists
-  WorldPos start_pos = m_Game->GetPlayer()->GetPosition();
-  for (const auto &next_pos : m_Game->GetPath()) {
-    const auto &camera = m_Game->GetCamera();
-    m_Window->DrawLine(camera.WorldToWindow(start_pos),
-                       camera.WorldToWindow(next_pos));
-    start_pos = next_pos;
+
+  for (const auto& entity : m_Game->GetEntities())
+  {
+    WorldPos start_pos = entity->GetPosition();
+    for (const auto &next_pos : entity->GetPath())
+    {
+      const auto &camera = m_Game->GetCamera();
+      m_Window->DrawLine(camera.WorldToWindow(start_pos),
+                         camera.WorldToWindow(next_pos));
+      start_pos = next_pos;
+    }
   }
 
   // draw all the entities (player etc)
   for (auto &entity : m_Game->GetEntities()) {
     const auto &camera = m_Game->GetCamera();
-    m_Window->DrawSprite(camera.WorldToWindow(entity->GetPosition()),
-                         entity->GetSprite(), camera.GetZoom());
+    auto entity_pos = camera.WorldToWindow(entity->GetPosition());
+    m_Window->DrawSprite(entity_pos,
+                         entity->GetSprite(),
+                         camera.GetZoom());
+    if (entity->IsCollisionBoxVisible())
+    {
+      float collision_radius = camera.WorldToWindowSize(entity->GetCollisionRadius());
+      m_Window->DrawCircle(entity_pos, collision_radius, 255, 0, 0);
+    }
+    if (entity->IsSelected())
+    {
+      float collision_radius = camera.WorldToWindowSize(entity->GetCollisionRadius());
+      m_Window->DrawCircle(entity_pos, collision_radius, 0, 255, 0);
+    }
   }
+
+  // draw the selection box, if present
+  if (m_Game->IsSelectionBoxActive())
+  {
+    const auto& [corner_pos, size] = m_Game->GetSelectionBoxPosSize();
+    m_Window->DrawRect(corner_pos, size, 200, 20, 20);
+  }
+
+
 }
 
 // TODO rethink coupling and dependencies in the game loop class
@@ -49,9 +75,10 @@ void GameLoop::Run() {
   LOG_INFO("Running the game");
   while (!m_Game->IsExitRequested()) {
     m_Game->HandleActions(m_UserInput->GetActions());
-    m_Game->UpdatePlayerVelocity();
+    m_Game->UpdateWorld();
 
     // TODO measure fps, draw only if delay for target fps was reached
+    // or create a separate thread for drawing
     m_Window->ClearWindow();
     Draw();
     m_Window->Flush();
diff --git a/cpp/src/math.hpp b/cpp/src/math.hpp
index fbd0682..be6e290 100644
--- a/cpp/src/math.hpp
+++ b/cpp/src/math.hpp
@@ -44,6 +44,8 @@ public:
     requires(std::same_as<ArgsT, T> && ...) && (sizeof...(ArgsT) == N)
   vec(ArgsT... args) : m_Array{args...} {}
 
+  vec(std::array<T, N> array) : m_Array{array} {}
+
   //
   // Access to elements & data
   //
@@ -165,6 +167,12 @@ public:
     return (a - b).Length();
   }
 
+  T DistanceSquared(const vec &b) const {
+    const vec &a = *this;
+    return (a - b).LengthSquared();
+  }
+
+
   //
   // In-place vector operations
   //
@@ -251,6 +259,12 @@ public:
     return m_Array[2];
   }
 
+  template <typename TargetTag>
+  vec<T,N,TargetTag> ChangeTag()
+  {
+    return vec<T,N,TargetTag>(m_Array);
+  }
+
 private:
   std::array<T, N> m_Array;
 };
@@ -394,4 +408,4 @@ public:
 
 private:
     std::array<vec_type, N> m_Array;
-};
\ No newline at end of file
+};
diff --git a/cpp/src/pathfindingdemo.cpp b/cpp/src/pathfindingdemo.cpp
index eef2382..7d8cd50 100644
--- a/cpp/src/pathfindingdemo.cpp
+++ b/cpp/src/pathfindingdemo.cpp
@@ -55,54 +55,108 @@ void PathFindingDemo::CreateMap() {
   m_Map.PaintLine(TilePos{84,81}, TilePos{84,96}, 1.0, TileType::WALL);
   m_Map.PaintLine(TilePos{78,87}, TilePos{78,100}, 1.0, TileType::WALL);
 
-  // add player
+  // add some controllable entities 
   m_Entities.clear();
-  m_Player = std::make_shared<Player>();
-  m_Player->SetPosition(m_Map.TileToWorld(TilePos{25, 20}));
-  m_Entities.push_back(m_Player);
+  auto player = std::make_shared<Player>();
+  player->SetPosition(m_Map.TileToWorld(TilePos{25, 20}));
+  AddEntity(player);
+
+  auto player2 = std::make_shared<Player>();
+  player2->SetPosition(m_Map.TileToWorld(TilePos{50, 20}));
+  AddEntity(player2);
+
+  for (int i = 0; i < 1; i++)
+  {
+    for (int j = 0; j < 10; j++)
+    {
+      auto p = std::make_shared<Player>();
+      p->SetPosition(m_Map.TileToWorld(TilePos{10+5*i, 40+5*j}));
+      AddEntity(p);
+    }
+  }
+
+  // select everything - TODO this is just temporary for testing
+  for (const auto& entity : m_Entities)
+  {
+    m_SelectedEntities.push_back(entity);
+  }
 }
 
 WorldPos PathFindingDemo::GetRandomPosition() const {
   return WorldPos{0.0f, 0.0f}; // totally random!
 }
 
-std::optional<WorldPos> PathFindingDemo::GetMoveTarget() {
-  WorldPos current_player_pos = GetPlayer()->GetPosition();
 
-  if (m_Path.empty()) {
-    return {};
+
+const std::vector<Collision>& PathFindingDemo::GetEntityCollisions()
+{
+  static std::vector<Collision> m_Collisions;
+  m_Collisions.clear();
+
+  for (const auto &entity_A : m_Entities)
+  {
+    for (const auto &entity_B : m_Entities)
+    {
+      if (entity_A == entity_B)
+        continue;
+      if (!entity_A->IsCollidable() || !entity_B->IsCollidable())
+        continue;
+      if (entity_A->CollidesWith(*entity_B))
+      {
+        // handle collision logic
+        m_Collisions.emplace_back(Collision(entity_A, entity_B));
+      }
+    }
   }
-
-  WorldPos next_player_pos = m_Path.front();
-
-  if (current_player_pos.DistanceTo(next_player_pos) > 1.0) {
-    // target not reached yet
-    return next_player_pos;
-  }
-  // target reached, pop it
-  //m_MoveQueue.pop();
-  m_Path.erase(m_Path.begin());
-  // return nothing - if there's next point in the queue,
-  // we'll get it in the next iteration
-  return {};
+  return m_Collisions;
 }
 
-void PathFindingDemo::UpdatePlayerVelocity() {
-  auto player = GetPlayer();
-  auto current_pos = player->GetPosition();
-  double tile_velocity_coeff = m_Map.GetTileVelocityCoeff(current_pos);
-  auto next_pos = GetMoveTarget();
-  WorldPos velocity = WorldPos{};
-  if (next_pos)
-  {
-    velocity = next_pos.value() - current_pos;
-    velocity.Normalize();
-    //LOG_DEBUG("I want to move to: ", next_pos.value(),
-    //          ", velocity: ", velocity);
-  }
-  player->SetActualVelocity(velocity * tile_velocity_coeff);
+
+// Update entity positions, handle collisions
+void PathFindingDemo::UpdateWorld() {
+  
   float time_delta = 1.0f;
-  player->Update(time_delta);
+  
+  for (auto& entity : m_Entities)
+  {
+    // calculate the velocity
+    auto current_pos = entity->GetPosition();
+    double tile_velocity_coeff = m_Map.GetTileVelocityCoeff(current_pos);
+    auto next_pos = entity->GetMoveTarget();
+    WorldPos velocity = WorldPos{};
+    if (next_pos)
+    {
+      velocity = next_pos.value() - current_pos;
+      velocity.Normalize();
+      //LOG_DEBUG("I want to move to: ", next_pos.value(),
+      //          ", velocity: ", velocity);
+    }
+    entity->SetActualVelocity(velocity * tile_velocity_coeff);
+    
+    for (const auto& collision : GetEntityCollisions())
+    {
+      // TODO this loop is quite "hot", is it good idea to use weak_ptr and promote it?
+      auto weak_A = std::get<0>(collision);
+      auto weak_B = std::get<1>(collision);
+      auto A = weak_A.lock();
+      auto B = weak_B.lock();
+      if (A == nullptr || B == nullptr)
+      {
+        continue;
+      }
+      if (!A->IsMovable())
+        continue;
+      // modify actual speed
+      // LOG_DEBUG("Collision: A is ", A, ", B is ", B);
+      auto AB = B->GetPosition() - A->GetPosition();
+      A->ZeroActualVelocityInDirection(AB);
+      // handle logic
+      // TODO
+    } 
+ 
+    // update the position
+    entity->Update(time_delta);
+  }
 }
 
 void PathFindingDemo::HandleActions(const std::vector<UserAction> &actions)
@@ -116,10 +170,19 @@ void PathFindingDemo::HandleActions(const std::vector<UserAction> &actions)
     }
     else if (action.type == UserAction::Type::SET_MOVE_TARGET)
     {
-      WorldPos wp = m_Camera.WindowToWorld(action.Argument.position);
-      LOG_INFO("Calculating path to target: ", wp);
-      m_Path = m_PathFinder->CalculatePath(m_Player->GetPosition(), wp);
-      LOG_INFO("Done, path node count: ", m_Path.size());
+      WorldPos target_pos = m_Camera.WindowToWorld(action.Argument.position);
+      for (auto& selected_entity : m_SelectedEntities)
+      {
+        LOG_INFO("Calculating path to target: ", target_pos);
+        if (auto sp = selected_entity.lock())
+        {
+          auto path = m_PathFinder->CalculatePath(sp->GetPosition(), target_pos);
+          sp->SetPath(path);
+          LOG_INFO("Done, path node count: ", path.size());
+        } else {
+          LOG_INFO("Cannot calculate path for destroyed entity (weak_ptr.lock() failed)");
+        }
+      }
     }
     else if (action.type == UserAction::Type::SELECT_PATHFINDER)
     {
@@ -140,5 +203,69 @@ void PathFindingDemo::HandleActions(const std::vector<UserAction> &actions)
       m_Camera.Zoom(action.Argument.float_number);
       LOG_INFO("Camera zoom: ", action.Argument.float_number);
     }
+    else if (action.type == UserAction::Type::SELECTION_START)
+    {
+      m_SelectionBox.active = true;
+      m_SelectionBox.start = action.Argument.position;
+      m_SelectionBox.end = action.Argument.position;
+    }
+    else if (action.type == UserAction::Type::SELECTION_END)
+    {
+      m_SelectionBox.end = action.Argument.position;
+      m_SelectionBox.active = false;
+      auto diff = m_SelectionBox.end - m_SelectionBox.start;
+      // here we explicitly change the vector type from WindowPos to WindowSize
+      m_SelectionBox.size = diff.ChangeTag<WindowSizeTag>();
+      WorldPos start = m_Camera.WindowToWorld(m_SelectionBox.start);
+      WorldPos end = m_Camera.WindowToWorld(m_SelectionBox.end);
+      SelectEntitiesInRectangle(start, end);
+    }
+    else if (action.type == UserAction::Type::SELECTION_CHANGE)
+    {
+      m_SelectionBox.end = action.Argument.position;
+      auto diff = m_SelectionBox.end - m_SelectionBox.start;
+      m_SelectionBox.size = diff.ChangeTag<WindowSizeTag>();
+    }
   };
 }
+
+void PathFindingDemo::DeselectEntities()
+{
+  std::for_each(m_SelectedEntities.begin(), m_SelectedEntities.end(), [](auto& x)
+      {
+        if (auto entity = x.lock())
+        entity->Deselect();
+      }
+  );
+  m_SelectedEntities.clear();
+}
+
+void PathFindingDemo::SelectEntitiesInRectangle(WorldPos A, WorldPos B)
+{
+  DeselectEntities();
+  // TODO use colliders for this
+  auto [x_min, x_max] = std::minmax(A.x(), B.x());
+  auto [y_min, y_max] = std::minmax(A.y(), B.y());
+  for (const auto& entity : m_Entities)
+  {
+    const auto& pos = entity->GetPosition();
+    bool x_in_range = x_min < pos.x() && pos.x() < x_max;
+    bool y_in_range = y_min < pos.y() && pos.y() < y_max;
+    if (x_in_range && y_in_range)
+    {
+      m_SelectedEntities.push_back(std::weak_ptr(entity));
+      entity->Select();
+    }
+  }
+  LOG_INFO("Selected ", m_SelectedEntities.size(), " entities");
+}
+
+std::pair<WindowPos, WindowSize> PathFindingDemo::GetSelectionBoxPosSize()
+{
+  const auto& pos = m_SelectionBox.start;
+  WindowPos size_pos = m_SelectionBox.end - m_SelectionBox.start;
+  WindowSize size = size_pos.ChangeTag<WindowSizeTag>();
+  return std::pair(pos, size);
+
+}
+
diff --git a/cpp/src/pathfindingdemo.hpp b/cpp/src/pathfindingdemo.hpp
index 9743c86..2f3eb4c 100644
--- a/cpp/src/pathfindingdemo.hpp
+++ b/cpp/src/pathfindingdemo.hpp
@@ -12,6 +12,15 @@
 #include "pathfinder/base.hpp"
 #include "camera.hpp"
 
+using Collision = std::pair<std::weak_ptr<Entity>, std::weak_ptr<Entity>>;
+
+struct SelectionBox
+{
+  WindowPos start, end;
+  WindowSize size;
+  bool active;
+};
+
 class PathFindingDemo {
 public:
   PathFindingDemo(int width, int height);
@@ -22,26 +31,31 @@ public:
   PathFindingDemo &operator=(const PathFindingDemo &) = delete;
   PathFindingDemo &operator=(PathFindingDemo &&) = delete;
 
-  std::shared_ptr<Player> GetPlayer() { return m_Player; }
   std::vector<std::shared_ptr<Entity>>& GetEntities() { return m_Entities; }
   const Map& GetMap() const { return m_Map; }
   const Camera& GetCamera() const { return m_Camera; }
-  const pathfinder::Path& GetPath() const { return m_Path; }
   bool IsExitRequested() const { return m_ExitRequested; }
 
   void AddEntity(std::shared_ptr<Entity> e);
   void CreateMap();
-  std::optional<WorldPos> GetMoveTarget();
-  void UpdatePlayerVelocity();
+  void UpdateWorld();
   void HandleActions(const std::vector<UserAction> &actions);
   WorldPos GetRandomPosition() const;
 
+  void SelectEntitiesInRectangle(WorldPos A, WorldPos B);
+  void DeselectEntities();
+  bool IsSelectionBoxActive() const { return m_SelectionBox.active; }
+  std::pair<WindowPos, WindowSize> GetSelectionBoxPosSize();
+  std::vector<std::weak_ptr<Entity>> GetSelectedEntities() { return m_SelectedEntities; }
+
 private:
+  const std::vector<Collision>& GetEntityCollisions();
+
   bool m_ExitRequested = false;
   Map m_Map;
   Camera m_Camera;
   std::vector<std::shared_ptr<Entity>> m_Entities;
-  std::shared_ptr<Player> m_Player;
-  pathfinder::Path m_Path;
   std::unique_ptr<pathfinder::PathFinderBase> m_PathFinder;
+  std::vector<std::weak_ptr<Entity>> m_SelectedEntities;
+  SelectionBox m_SelectionBox;
 };
diff --git a/cpp/src/user_input.cpp b/cpp/src/user_input.cpp
index 1604f94..ae9895f 100644
--- a/cpp/src/user_input.cpp
+++ b/cpp/src/user_input.cpp
@@ -31,7 +31,14 @@ void UserInput::GetActions_mouse(const SDL_Event& event)
   {
     if (button == MouseButton::LEFT)
     {
-      LOG_DEBUG("Mouse down: ", mouse_event.x, ", ", mouse_event.y);
+      LOG_DEBUG("Selection start at ", mouse_event.x, ", ", mouse_event.y);
+      m_SelectionActive = true;
+      m_Actions.emplace_back(UserAction::Type::SELECTION_START,
+                             WindowPos{mouse_event.x, mouse_event.y});
+    }
+    else if (button == MouseButton::RIGHT)
+    {
+      LOG_DEBUG("Set move target to: ", mouse_event.x, ", ", mouse_event.y);
       m_Actions.emplace_back(UserAction::Type::SET_MOVE_TARGET,
                              WindowPos{mouse_event.x, mouse_event.y});
     }
@@ -42,6 +49,13 @@ void UserInput::GetActions_mouse(const SDL_Event& event)
   }
   else if (event.type == SDL_EVENT_MOUSE_BUTTON_UP)
   {
+    if (button == MouseButton::LEFT)
+    {
+      LOG_DEBUG("Selection end at ", mouse_event.x, ", ", mouse_event.y);
+      m_SelectionActive = false;
+      m_Actions.emplace_back(UserAction::Type::SELECTION_END,
+                             WindowPos{mouse_event.x, mouse_event.y});
+    }
     if (button == MouseButton::MIDDLE)
     {
       mouse_pan = false;
@@ -55,6 +69,11 @@ void UserInput::GetActions_mouse(const SDL_Event& event)
       m_Actions.emplace_back(UserAction::Type::CAMERA_PAN,
                              WindowPos{motion_event.xrel, motion_event.yrel});  
     }
+    if (m_SelectionActive)
+    {
+      m_Actions.emplace_back(UserAction::Type::SELECTION_CHANGE,
+                             WindowPos{mouse_event.x, mouse_event.y});
+    }
   }
   else if(event.type == SDL_EVENT_MOUSE_WHEEL)
   {
diff --git a/cpp/src/user_input.hpp b/cpp/src/user_input.hpp
index c32b071..dee9231 100644
--- a/cpp/src/user_input.hpp
+++ b/cpp/src/user_input.hpp
@@ -12,7 +12,19 @@ enum class MouseButton { LEFT = 1, MIDDLE, RIGHT };
 
 class UserAction {
 public:
-  enum class Type { NONE, EXIT, SET_MOVE_TARGET, SELECT_PATHFINDER, CAMERA_PAN, CAMERA_ZOOM };
+
+  enum class Type
+  {
+    NONE,
+    EXIT,
+    SET_MOVE_TARGET,
+    SELECT_PATHFINDER,
+    CAMERA_PAN,
+    CAMERA_ZOOM,
+    SELECTION_START,
+    SELECTION_CHANGE,
+    SELECTION_END
+  };
 
   UserAction() : type(Type::NONE), Argument{.number = 0} {}
   UserAction(Type t) : type(t), Argument{.number = 0} {}
@@ -51,6 +63,7 @@ public:
 
 private:
   std::vector<UserAction> m_Actions;
+  bool m_SelectionActive = false;
 
   void GetActions_keyboard(const SDL_Event&);
   void GetActions_mouse(const SDL_Event&);
diff --git a/cpp/src/window.cpp b/cpp/src/window.cpp
index 91b9ab6..f92bfcc 100644
--- a/cpp/src/window.cpp
+++ b/cpp/src/window.cpp
@@ -84,13 +84,19 @@ void Window::DrawSprite(const WindowPos &position, Sprite &s, float scale) {
   SDL_RenderTexture(m_Renderer.get(), s.GetTexture(), nullptr, &rect);
 }
 
-void Window::DrawRect(const WindowPos &position, const WindowSize size, uint8_t R,
+void Window::DrawFilledRect(const WindowPos &position, const WindowSize size, uint8_t R,
                       uint8_t G, uint8_t B, uint8_t A) {
   SDL_FRect rect = {position.x(), position.y(), size.x(), size.y()};
   SDL_SetRenderDrawColor(m_Renderer.get(), R, G, B, A);
   SDL_RenderFillRect(m_Renderer.get(), &rect);
 }
 
+void Window::DrawRect(const WindowPos &position, const WindowSize size, uint8_t R, uint8_t G, uint8_t B) {
+  SDL_FRect rect = {position.x(), position.y(), size.x(), size.y()};
+  SDL_SetRenderDrawColor(m_Renderer.get(), R, G, B, 255);
+  SDL_RenderRect(m_Renderer.get(), &rect);
+}
+
 void Window::ClearWindow() {
   SDL_SetRenderDrawColor(m_Renderer.get(), 50, 50, 50, 255);
   SDL_RenderClear(m_Renderer.get());
@@ -98,10 +104,11 @@ void Window::ClearWindow() {
 
 void Window::Flush() { SDL_RenderPresent(m_Renderer.get()); }
 
-void Window::DrawCircle(const WindowPos &position, float radius) {
+// TODO use some struct for color
+void Window::DrawCircle(const WindowPos &position, float radius, uint8_t R, uint8_t G, uint8_t B) {
   int cx = static_cast<int>(position.x());
   int cy = static_cast<int>(position.y());
-  SDL_SetRenderDrawColor(m_Renderer.get(), 255, 0, 0, 255);
+  SDL_SetRenderDrawColor(m_Renderer.get(), R, G, B, 255);
   for (int i = 0; i < 360; ++i) {
     double a = i * M_PI / 180.0;
     SDL_RenderPoint(m_Renderer.get(),
diff --git a/cpp/src/window.hpp b/cpp/src/window.hpp
index 8453d67..0729bd4 100644
--- a/cpp/src/window.hpp
+++ b/cpp/src/window.hpp
@@ -23,11 +23,12 @@ public:
 
   std::expected<void, std::string> Init();
   void DrawSprite(const WindowPos &position, Sprite &s, float scale = 1.0f);
-  void DrawRect(const WindowPos &position, const WindowSize size, uint8_t R,
+  void DrawFilledRect(const WindowPos &position, const WindowSize size, uint8_t R,
                 uint8_t G, uint8_t B, uint8_t A);
+  void DrawRect(const WindowPos &position, const WindowSize size, uint8_t R, uint8_t G, uint8_t B);
   void ClearWindow();
   void Flush();
-  void DrawCircle(const WindowPos &position, float radius);
+  void DrawCircle(const WindowPos &position, float radius, uint8_t R, uint8_t G, uint8_t B);
   void DrawLine(const WindowPos &A, const WindowPos &B);
 
 private:
diff --git a/cpp/test/test.cpp b/cpp/test/test.cpp
index 8b9262b..b94b846 100644
--- a/cpp/test/test.cpp
+++ b/cpp/test/test.cpp
@@ -26,6 +26,37 @@ TEST(vec, GetElements) {
   ASSERT_EQ(v1[2], 56);
 }
 
+TEST(vec, ArrayConstruction) {
+  // Test construction from std::array
+  std::array<float, 3> arr3{1.5f, 2.5f, 3.5f};
+  vec3 v1(arr3);
+  
+  ASSERT_FLOAT_EQ(v1[0], 1.5f);
+  ASSERT_FLOAT_EQ(v1[1], 2.5f);
+  ASSERT_FLOAT_EQ(v1[2], 3.5f);
+  
+  // Test with 2D vector
+  std::array<float, 2> arr2{10.0f, 20.0f};
+  vec2 v2(arr2);
+  
+  ASSERT_FLOAT_EQ(v2[0], 10.0f);
+  ASSERT_FLOAT_EQ(v2[1], 20.0f);
+  
+  // Test with integer vector
+  std::array<int32_t, 4> arr4{1, 2, 3, 4};
+  ivec4 v4(arr4);
+  
+  ASSERT_EQ(v4[0], 1);
+  ASSERT_EQ(v4[1], 2);
+  ASSERT_EQ(v4[2], 3);
+  ASSERT_EQ(v4[3], 4);
+  
+  // Test that original array is unchanged
+  ASSERT_FLOAT_EQ(arr3[0], 1.5f);
+  ASSERT_FLOAT_EQ(arr3[1], 2.5f);
+  ASSERT_FLOAT_EQ(arr3[2], 3.5f);
+}
+
 
 TEST(vec, equalEpsilon) {
   // Test equalEpsilon
@@ -430,6 +461,43 @@ TEST(vec, ChainedOperations) {
   ASSERT_FLOAT_EQ(a[1], 3.0f);
 }
 
+TEST(vec, ChangeTag) {
+  // Test changing tag from WorldPos to WindowPos
+  WorldPos world_pos{100.0f, 200.0f};
+  WindowPos window_pos = world_pos.ChangeTag<WindowPosTag>();
+  
+  // Data should be preserved
+  ASSERT_FLOAT_EQ(window_pos[0], 100.0f);
+  ASSERT_FLOAT_EQ(window_pos[1], 200.0f);
+  
+  // Original should be unchanged
+  ASSERT_FLOAT_EQ(world_pos[0], 100.0f);
+  ASSERT_FLOAT_EQ(world_pos[1], 200.0f);
+  
+  // Test changing tag from TilePos to another tag
+  TilePos tile_pos{5, 10};
+  auto generic_pos = tile_pos.ChangeTag<Any>();
+  
+  ASSERT_EQ(generic_pos[0], 5);
+  ASSERT_EQ(generic_pos[1], 10);
+  
+  // Test with 3D vector and custom tag
+  struct CustomTag {};
+  vec3 original{1.5f, 2.5f, 3.5f};
+  vec<float, 3, CustomTag> custom_tagged = original.ChangeTag<CustomTag>();
+  
+  ASSERT_FLOAT_EQ(custom_tagged[0], 1.5f);
+  ASSERT_FLOAT_EQ(custom_tagged[1], 2.5f);
+  ASSERT_FLOAT_EQ(custom_tagged[2], 3.5f);
+  
+  // Test that we can change back
+  vec3 back_to_original = custom_tagged.ChangeTag<Any>();
+  
+  ASSERT_FLOAT_EQ(back_to_original[0], 1.5f);
+  ASSERT_FLOAT_EQ(back_to_original[1], 2.5f);
+  ASSERT_FLOAT_EQ(back_to_original[2], 3.5f);
+}
+
 TEST(Matrix, DefaultConstruction) {
   // Test that default-constructed matrix has all elements equal to zero
   Matrix<float, 2> m1;