diff --git a/source/ui/ui_manager.cpp b/source/ui/ui_manager.cpp
index 2ca1ae4..fda4c1a 100644
--- a/source/ui/ui_manager.cpp
+++ b/source/ui/ui_manager.cpp
@@ -205,6 +205,11 @@ void UIManager::renderDebugHUD(const Engine* engine,
     int line_height = text_renderer_debug_->getTextHeight();
     int margin = 8;  // Margen constante en píxeles físicos
 
+    // Obtener viewport actual (en modo letterbox F3 tiene dimensiones más pequeñas)
+    // CRÍTICO: Usar dimensiones del VIEWPORT para alineación, no de la ventana física
+    SDL_Rect viewport;
+    SDL_GetRenderViewport(renderer_, &viewport);
+
     // ===========================
     // COLUMNA LEFT (Sistema)
     // ===========================
@@ -307,7 +312,7 @@ void UIManager::renderDebugHUD(const Engine* engine,
 
     // FPS counter (esquina superior derecha)
     int fps_text_width = text_renderer_debug_->getTextWidthPhysical(fps_text_.c_str());
-    int fps_x = physical_window_width_ - fps_text_width - margin;
+    int fps_x = viewport.w - fps_text_width - margin;
     text_renderer_debug_->printAbsolute(fps_x, right_y, fps_text_.c_str(), {255, 255, 0, 255});  // Amarillo
     right_y += line_height;
 
@@ -318,47 +323,47 @@ void UIManager::renderDebugHUD(const Engine* engine,
         SDL_FRect pos = first_ball->getPosition();
         std::string pos_text = "Pos: (" + std::to_string(static_cast<int>(pos.x)) + ", " + std::to_string(static_cast<int>(pos.y)) + ")";
         int pos_width = text_renderer_debug_->getTextWidthPhysical(pos_text.c_str());
-        text_renderer_debug_->printAbsolute(physical_window_width_ - pos_width - margin, right_y, pos_text.c_str(), {255, 128, 128, 255});  // Rojo claro
+        text_renderer_debug_->printAbsolute(viewport.w - pos_width - margin, right_y, pos_text.c_str(), {255, 128, 128, 255});  // Rojo claro
         right_y += line_height;
 
         // Velocidad X
         int vx_int = static_cast<int>(first_ball->getVelocityX());
         std::string vx_text = "VelX: " + std::to_string(vx_int);
         int vx_width = text_renderer_debug_->getTextWidthPhysical(vx_text.c_str());
-        text_renderer_debug_->printAbsolute(physical_window_width_ - vx_width - margin, right_y, vx_text.c_str(), {128, 255, 128, 255});  // Verde claro
+        text_renderer_debug_->printAbsolute(viewport.w - vx_width - margin, right_y, vx_text.c_str(), {128, 255, 128, 255});  // Verde claro
         right_y += line_height;
 
         // Velocidad Y
         int vy_int = static_cast<int>(first_ball->getVelocityY());
         std::string vy_text = "VelY: " + std::to_string(vy_int);
         int vy_width = text_renderer_debug_->getTextWidthPhysical(vy_text.c_str());
-        text_renderer_debug_->printAbsolute(physical_window_width_ - vy_width - margin, right_y, vy_text.c_str(), {128, 255, 128, 255});  // Verde claro
+        text_renderer_debug_->printAbsolute(viewport.w - vy_width - margin, right_y, vy_text.c_str(), {128, 255, 128, 255});  // Verde claro
         right_y += line_height;
 
         // Fuerza de gravedad
         int grav_int = static_cast<int>(first_ball->getGravityForce());
         std::string grav_text = "Gravity: " + std::to_string(grav_int);
         int grav_width = text_renderer_debug_->getTextWidthPhysical(grav_text.c_str());
-        text_renderer_debug_->printAbsolute(physical_window_width_ - grav_width - margin, right_y, grav_text.c_str(), {255, 255, 128, 255});  // Amarillo claro
+        text_renderer_debug_->printAbsolute(viewport.w - grav_width - margin, right_y, grav_text.c_str(), {255, 255, 128, 255});  // Amarillo claro
         right_y += line_height;
 
         // Estado superficie
         std::string surface_text = first_ball->isOnSurface() ? "Surface: YES" : "Surface: NO";
         int surface_width = text_renderer_debug_->getTextWidthPhysical(surface_text.c_str());
-        text_renderer_debug_->printAbsolute(physical_window_width_ - surface_width - margin, right_y, surface_text.c_str(), {255, 200, 128, 255});  // Naranja claro
+        text_renderer_debug_->printAbsolute(viewport.w - surface_width - margin, right_y, surface_text.c_str(), {255, 200, 128, 255});  // Naranja claro
         right_y += line_height;
 
         // Coeficiente de rebote (loss)
         float loss_val = first_ball->getLossCoefficient();
         std::string loss_text = "Loss: " + std::to_string(loss_val).substr(0, 4);
         int loss_width = text_renderer_debug_->getTextWidthPhysical(loss_text.c_str());
-        text_renderer_debug_->printAbsolute(physical_window_width_ - loss_width - margin, right_y, loss_text.c_str(), {255, 128, 255, 255});  // Magenta
+        text_renderer_debug_->printAbsolute(viewport.w - loss_width - margin, right_y, loss_text.c_str(), {255, 128, 255, 255});  // Magenta
         right_y += line_height;
 
         // Dirección de gravedad
         std::string gravity_dir_text = "Dir: " + gravityDirectionToString(static_cast<int>(scene_manager->getCurrentGravity()));
         int dir_width = text_renderer_debug_->getTextWidthPhysical(gravity_dir_text.c_str());
-        text_renderer_debug_->printAbsolute(physical_window_width_ - dir_width - margin, right_y, gravity_dir_text.c_str(), {128, 255, 255, 255});  // Cian claro
+        text_renderer_debug_->printAbsolute(viewport.w - dir_width - margin, right_y, gravity_dir_text.c_str(), {128, 255, 255, 255});  // Cian claro
         right_y += line_height;
     }
 
@@ -367,7 +372,7 @@ void UIManager::renderDebugHUD(const Engine* engine,
         int convergence_percent = static_cast<int>(shape_convergence * 100.0f);
         std::string convergence_text = "Convergence: " + std::to_string(convergence_percent) + "%";
         int conv_width = text_renderer_debug_->getTextWidthPhysical(convergence_text.c_str());
-        text_renderer_debug_->printAbsolute(physical_window_width_ - conv_width - margin, right_y, convergence_text.c_str(), {255, 128, 0, 255});  // Naranja
+        text_renderer_debug_->printAbsolute(viewport.w - conv_width - margin, right_y, convergence_text.c_str(), {255, 128, 0, 255});  // Naranja
         right_y += line_height;
     }
 }