diff --git a/source/engine.cpp b/source/engine.cpp
index 2306355..73c7fd1 100644
--- a/source/engine.cpp
+++ b/source/engine.cpp
@@ -718,34 +718,31 @@ void Engine::render() {
         // MODO FIGURA 3D: Ordenar por profundidad Z (Painter's Algorithm)
         // Las pelotas con menor depth_brightness (más lejos/oscuras) se renderizan primero
 
-        // Crear vector de índices para ordenamiento
-        std::vector<size_t> render_order;
-        render_order.reserve(balls.size());
+        // Bucket sort per profunditat Z (O(N) vs O(N log N))
         for (size_t i = 0; i < balls.size(); i++) {
-            render_order.push_back(i);
+            int b = static_cast<int>(balls[i]->getDepthBrightness() * (DEPTH_SORT_BUCKETS - 1));
+            depth_buckets_[std::clamp(b, 0, DEPTH_SORT_BUCKETS - 1)].push_back(i);
         }
 
-        // Ordenar índices por profundidad Z (menor primero = fondo primero)
-        std::sort(render_order.begin(), render_order.end(), [&balls](size_t a, size_t b) {
-            return balls[a]->getDepthBrightness() < balls[b]->getDepthBrightness();
-        });
+        // Renderizar en orden de profundidad (bucket 0 = fons, bucket 255 = davant)
+        for (int b = 0; b < DEPTH_SORT_BUCKETS; b++) {
+            for (size_t idx : depth_buckets_[b]) {
+                SDL_FRect pos = balls[idx]->getPosition();
+                Color color = theme_manager_->getInterpolatedColor(idx);  // Usar color interpolado (LERP)
+                float brightness = balls[idx]->getDepthBrightness();
+                float depth_scale = balls[idx]->getDepthScale();
 
-        // Renderizar en orden de profundidad (fondo → frente)
-        for (size_t idx : render_order) {
-            SDL_FRect pos = balls[idx]->getPosition();
-            Color color = theme_manager_->getInterpolatedColor(idx);  // Usar color interpolado (LERP)
-            float brightness = balls[idx]->getDepthBrightness();
-            float depth_scale = balls[idx]->getDepthScale();
+                // Mapear brightness de 0-1 a rango MIN-MAX
+                float brightness_factor = (ROTOBALL_MIN_BRIGHTNESS + brightness * (ROTOBALL_MAX_BRIGHTNESS - ROTOBALL_MIN_BRIGHTNESS)) / 255.0f;
 
-            // Mapear brightness de 0-1 a rango MIN-MAX
-            float brightness_factor = (ROTOBALL_MIN_BRIGHTNESS + brightness * (ROTOBALL_MAX_BRIGHTNESS - ROTOBALL_MIN_BRIGHTNESS)) / 255.0f;
+                // Aplicar factor de brillo al color
+                int r_mod = static_cast<int>(color.r * brightness_factor);
+                int g_mod = static_cast<int>(color.g * brightness_factor);
+                int b_mod = static_cast<int>(color.b * brightness_factor);
 
-            // Aplicar factor de brillo al color
-            int r_mod = static_cast<int>(color.r * brightness_factor);
-            int g_mod = static_cast<int>(color.g * brightness_factor);
-            int b_mod = static_cast<int>(color.b * brightness_factor);
-
-            addSpriteToBatch(pos.x, pos.y, pos.w, pos.h, r_mod, g_mod, b_mod, depth_scale);
+                addSpriteToBatch(pos.x, pos.y, pos.w, pos.h, r_mod, g_mod, b_mod, depth_scale);
+            }
+            depth_buckets_[b].clear();  // netejar per al proper frame
         }
     } else {
         // MODO PHYSICS: Renderizar en orden normal del vector (sin escala de profundidad)
diff --git a/source/engine.hpp b/source/engine.hpp
index 3e6b5fe..01bd665 100644
--- a/source/engine.hpp
+++ b/source/engine.hpp
@@ -223,6 +223,10 @@ class Engine {
         std::vector<SDL_Vertex> batch_vertices_;
         std::vector<int> batch_indices_;
 
+        // Bucket sort per z-ordering (SHAPE mode)
+        static constexpr int DEPTH_SORT_BUCKETS = 256;
+        std::array<std::vector<size_t>, DEPTH_SORT_BUCKETS> depth_buckets_;
+
         // Configuración del sistema de texto (constantes configurables)
         static constexpr const char* TEXT_FONT_PATH = "data/fonts/determination.ttf";
         static constexpr int TEXT_BASE_SIZE = 24;        // Tamaño base para 240p