diff --git a/source/ball.cpp b/source/ball.cpp
index 15c7884..7569fa9 100644
--- a/source/ball.cpp
+++ b/source/ball.cpp
@@ -22,9 +22,9 @@ float generateLateralLoss() {
 }
 
 // Constructor
-Ball::Ball(float x, float vx, float vy, Color color, std::shared_ptr<Texture> texture, int screen_width, int screen_height, int ball_size, GravityDirection gravity_dir, float mass_factor)
+Ball::Ball(float x, float y, float vx, float vy, Color color, std::shared_ptr<Texture> texture, int screen_width, int screen_height, int ball_size, GravityDirection gravity_dir, float mass_factor)
     : sprite_(std::make_unique<Sprite>(texture)),
-      pos_({x, 0.0f, static_cast<float>(ball_size), static_cast<float>(ball_size)}) {
+      pos_({x, y, static_cast<float>(ball_size), static_cast<float>(ball_size)}) {
     // Convertir velocidades de píxeles/frame a píxeles/segundo (multiplicar por 60)
     vx_ = vx * 60.0f;
     vy_ = vy * 60.0f;
diff --git a/source/ball.h b/source/ball.h
index a0545d2..432e3ac 100644
--- a/source/ball.h
+++ b/source/ball.h
@@ -31,7 +31,7 @@ class Ball {
 
     public:
         // Constructor
-        Ball(float x, float vx, float vy, Color color, std::shared_ptr<Texture> texture, int screen_width, int screen_height, int ball_size, GravityDirection gravity_dir = GravityDirection::DOWN, float mass_factor = 1.0f);
+        Ball(float x, float y, float vx, float vy, Color color, std::shared_ptr<Texture> texture, int screen_width, int screen_height, int ball_size, GravityDirection gravity_dir = GravityDirection::DOWN, float mass_factor = 1.0f);
 
         // Destructor
         ~Ball() = default;
diff --git a/source/engine.cpp b/source/engine.cpp
index de871e6..c356c2d 100644
--- a/source/engine.cpp
+++ b/source/engine.cpp
@@ -514,6 +514,12 @@ void Engine::changeScenario(int scenario_id, const char* notification_text) {
     // Si estamos en modo SHAPE, regenerar la figura con nuevo número de pelotas
     if (current_mode_ == SimulationMode::SHAPE) {
         generateShape();
+
+        // Activar atracción física en las bolas nuevas (crítico tras changeScenario)
+        auto& balls = scene_manager_->getBallsMutable();
+        for (auto& ball : balls) {
+            ball->enableShapeAttraction(true);
+        }
     }
 
     showNotificationForAction(notification_text);
diff --git a/source/scene/scene_manager.cpp b/source/scene/scene_manager.cpp
index b1674c0..e731fa3 100644
--- a/source/scene/scene_manager.cpp
+++ b/source/scene/scene_manager.cpp
@@ -45,7 +45,7 @@ void SceneManager::changeScenario(int scenario_id, SimulationMode mode) {
 
     // Crear las bolas según el escenario
     for (int i = 0; i < BALL_COUNT_SCENARIOS[scenario_id]; ++i) {
-        float X, VX, VY;
+        float X, Y, VX, VY;
 
         // Inicialización según SimulationMode (RULES.md líneas 23-26)
         switch (mode) {
@@ -55,6 +55,7 @@ void SceneManager::changeScenario(int scenario_id, SimulationMode mode) {
                 const int margin = static_cast<int>(screen_width_ * BALL_SPAWN_MARGIN);
                 const int spawn_zone_width = screen_width_ - (2 * margin);
                 X = (rand() % spawn_zone_width) + margin;
+                Y = 0.0f;  // Parte superior
                 VX = (((rand() % 20) + 10) * 0.1f) * SIGN;
                 VY = ((rand() % 60) - 30) * 0.1f;
                 break;
@@ -63,6 +64,7 @@ void SceneManager::changeScenario(int scenario_id, SimulationMode mode) {
             case SimulationMode::SHAPE: {
                 // SHAPE: Centro de pantalla, sin velocidad inicial
                 X = screen_width_ / 2.0f;
+                Y = screen_height_ / 2.0f;  // Centro vertical
                 VX = 0.0f;
                 VY = 0.0f;
                 break;
@@ -73,6 +75,7 @@ void SceneManager::changeScenario(int scenario_id, SimulationMode mode) {
                 const int SIGN_X = ((rand() % 2) * 2) - 1;
                 const int SIGN_Y = ((rand() % 2) * 2) - 1;
                 X = static_cast<float>(rand() % screen_width_);
+                Y = static_cast<float>(rand() % screen_height_);  // Posición Y aleatoria
                 VX = (((rand() % 40) + 10) * 0.1f) * SIGN_X;  // 1.0 - 5.0 px/frame
                 VY = (((rand() % 40) + 10) * 0.1f) * SIGN_Y;
                 break;
@@ -84,6 +87,7 @@ void SceneManager::changeScenario(int scenario_id, SimulationMode mode) {
                 const int margin = static_cast<int>(screen_width_ * BALL_SPAWN_MARGIN);
                 const int spawn_zone_width = screen_width_ - (2 * margin);
                 X = (rand() % spawn_zone_width) + margin;
+                Y = 0.0f;  // Parte superior
                 VX = (((rand() % 20) + 10) * 0.1f) * SIGN;
                 VY = ((rand() % 60) - 30) * 0.1f;
                 break;
@@ -97,7 +101,7 @@ void SceneManager::changeScenario(int scenario_id, SimulationMode mode) {
         float mass_factor = GRAVITY_MASS_MIN + (rand() % 1000) / 1000.0f * (GRAVITY_MASS_MAX - GRAVITY_MASS_MIN);
 
         balls_.emplace_back(std::make_unique<Ball>(
-            X, VX, VY, COLOR, texture_,
+            X, Y, VX, VY, COLOR, texture_,
             screen_width_, screen_height_, current_ball_size_,
             current_gravity_, mass_factor
         ));