corregit: en el mode demo no calculava correctament el estat del fondo

source/stage.cpp

@@ -151,6 +151,51 @@ auto StageManager::jumpToStage(size_t target_stage_index) -> bool {
     return true;
 }
 
+auto StageManager::setTotalPower(int target_total_power) -> bool {
+    if (target_total_power < 0) {
+        return false;
+    }
+
+    int total_power_needed = getTotalPowerNeededToCompleteGame();
+    if (target_total_power > total_power_needed) {
+        return false;
+    }
+
+    // Calcular en qué fase debería estar y cuánto poder de esa fase
+    int accumulated_power = 0;
+    size_t target_stage_index = 0;
+    int target_current_power = 0;
+
+    for (size_t i = 0; i < stages_.size(); ++i) {
+        int stage_power = stages_[i].getPowerToComplete();
+
+        if (accumulated_power + stage_power > target_total_power) {
+            // El objetivo está dentro de esta fase
+            target_stage_index = i;
+            target_current_power = target_total_power - accumulated_power;
+            break;
+        }
+
+        accumulated_power += stage_power;
+
+        if (accumulated_power == target_total_power) {
+            // El objetivo coincide exactamente con el final de esta fase
+            // Mover a la siguiente fase (si existe) con power 0
+            target_stage_index = (i + 1 < stages_.size()) ? i + 1 : i;
+            target_current_power = (i + 1 < stages_.size()) ? 0 : stage_power;
+            break;
+        }
+    }
+
+    // Actualizar estado
+    current_stage_index_ = target_stage_index;
+    current_power_ = target_current_power;
+    total_power_ = target_total_power;
+
+    updateStageStatuses();
+    return true;
+}
+
 auto StageManager::subtractPower(int amount) -> bool {
     if (amount <= 0 || current_power_ < amount) {
         return false;