diff --git a/Include/MyIncludes/VIDYA_Stdev_Calculator.mqh b/Include/MyIncludes/VIDYA_Stdev_Calculator.mqh
new file mode 100644
index 0000000..ee6cc6f
--- /dev/null
+++ b/Include/MyIncludes/VIDYA_Stdev_Calculator.mqh
@@ -0,0 +1,213 @@
+//+------------------------------------------------------------------+
+//|                                         VIDYA_Stdev_Calculator.mqh |
+//|      VERSION 1.20: Corrected Stdev to manual calculation.        |
+//|                                        Copyright 2025, xxxxxxxx  |
+//+------------------------------------------------------------------+
+#property copyright "Copyright 2025, xxxxxxxx"
+
+#include <MyIncludes\HeikinAshi_Tools.mqh>
+
+//+==================================================================+
+class CVIDYAStdevCalculator
+  {
+protected:
+   int               m_vidya_period, m_stdev_short, m_stdev_long;
+   double            m_price[];
+   double            m_prev_vidya;
+
+   virtual bool      PreparePriceSeries(int rates_total, ENUM_APPLIED_PRICE price_type, const double &open[], const double &high[], const double &low[], const double &close[]);
+   //--- Helper function for manual Standard Deviation calculation ---
+   double            CalculateStdDev(const double &array[], int period, int position);
+
+public:
+                     CVIDYAStdevCalculator(void) : m_prev_vidya(0) {};
+   virtual          ~CVIDYAStdevCalculator(void) {};
+
+   bool              Init(int vidya_p, int stdev_s, int stdev_l);
+   void              Calculate(int rates_total, ENUM_APPLIED_PRICE price_type, const double &open[], const double &high[], const double &low[], const double &close[], double &vidya_buffer[]);
+  };
+
+//+------------------------------------------------------------------+
+//|                                                                  |
+//+------------------------------------------------------------------+
+class CVIDYAStdevCalculator_HA : public CVIDYAStdevCalculator
+  {
+private:
+   CHeikinAshi_Calculator m_ha_calculator;
+protected:
+   virtual bool      PreparePriceSeries(int rates_total, ENUM_APPLIED_PRICE price_type, const double &open[], const double &high[], const double &low[], const double &close[]) override;
+  };
+
+//+==================================================================+
+//|                 METHOD IMPLEMENTATIONS                           |
+//+==================================================================+
+
+//+------------------------------------------------------------------+
+//|                                                                  |
+//+------------------------------------------------------------------+
+bool CVIDYAStdevCalculator::Init(int vidya_p, int stdev_s, int stdev_l)
+  {
+   m_vidya_period = (vidya_p < 1) ? 1 : vidya_p;
+   m_stdev_short = (stdev_s < 1) ? 1 : stdev_s;
+   m_stdev_long = (stdev_l <= m_stdev_short) ? m_stdev_short + 1 : stdev_l;
+   m_prev_vidya = 0;
+   return true;
+  }
+
+//+------------------------------------------------------------------+
+//|                                                                  |
+//+------------------------------------------------------------------+
+void CVIDYAStdevCalculator::Calculate(int rates_total, ENUM_APPLIED_PRICE price_type, const double &open[], const double &high[], const double &low[], const double &close[], double &vidya_buffer[])
+  {
+   if(rates_total <= m_stdev_long)
+      return;
+   if(!PreparePriceSeries(rates_total, price_type, open, high, low, close))
+      return;
+
+   double stdev_short_buff[], stdev_long_buff[];
+   ArrayResize(stdev_short_buff, rates_total);
+   ArrayResize(stdev_long_buff, rates_total);
+
+//--- STEP 1: Calculate Standard Deviations manually ---
+   for(int i = m_stdev_long - 1; i < rates_total; i++)
+     {
+      if(i >= m_stdev_short - 1)
+         stdev_short_buff[i] = CalculateStdDev(m_price, m_stdev_short, i);
+
+      stdev_long_buff[i] = CalculateStdDev(m_price, m_stdev_long, i);
+     }
+
+//--- STEP 2: Calculate VIDYA
+   double alpha = 2.0 / (m_vidya_period + 1.0);
+   int start_pos = m_stdev_long;
+
+   if(ArraySize(vidya_buffer) == 0 || vidya_buffer[start_pos-1] == 0)
+     {
+      m_prev_vidya = m_price[start_pos-1];
+     }
+
+   for(int i = start_pos; i < rates_total; i++)
+     {
+      double k = (stdev_long_buff[i] > 0.000001) ? stdev_short_buff[i] / stdev_long_buff[i] : 1.0;
+
+      double alpha_k = alpha * k;
+      if(alpha_k > 1.0)
+         alpha_k = 1.0;
+
+      vidya_buffer[i] = m_price[i] * alpha_k + m_prev_vidya * (1.0 - alpha_k);
+
+      m_prev_vidya = vidya_buffer[i];
+     }
+  }
+
+//--- NEW: Helper function for manual Standard Deviation calculation ---
+double CVIDYAStdevCalculator::CalculateStdDev(const double &array[], int period, int position)
+  {
+   if(position < period - 1)
+      return 0.0;
+
+// 1. Calculate the average (SMA)
+   double sum = 0;
+   for(int i = 0; i < period; i++)
+      sum += array[position - i];
+   double avg = sum / period;
+
+// 2. Calculate the sum of squared differences
+   double sum_sq = 0;
+   for(int i = 0; i < period; i++)
+      sum_sq += pow(array[position - i] - avg, 2);
+
+// 3. Return the standard deviation
+   return sqrt(sum_sq / period);
+  }
+
+//+------------------------------------------------------------------+
+//|                                                                  |
+//+------------------------------------------------------------------+
+bool CVIDYAStdevCalculator::PreparePriceSeries(int rates_total, ENUM_APPLIED_PRICE price_type, const double &open[], const double &high[], const double &low[], const double &close[])
+  {
+   if(ArraySize(m_price) != rates_total)
+      if(ArrayResize(m_price, rates_total) != rates_total)
+         return false;
+
+   switch(price_type)
+     {
+      case PRICE_CLOSE:
+         ArrayCopy(m_price, close, 0, 0, rates_total);
+         break;
+      case PRICE_OPEN:
+         ArrayCopy(m_price, open, 0, 0, rates_total);
+         break;
+      case PRICE_HIGH:
+         ArrayCopy(m_price, high, 0, 0, rates_total);
+         break;
+      case PRICE_LOW:
+         ArrayCopy(m_price, low, 0, 0, rates_total);
+         break;
+      case PRICE_MEDIAN:
+         for(int i=0; i<rates_total; i++)
+            m_price[i] = (high[i]+low[i])/2.0;
+         break;
+      case PRICE_TYPICAL:
+         for(int i=0; i<rates_total; i++)
+            m_price[i] = (high[i]+low[i]+close[i])/3.0;
+         break;
+      case PRICE_WEIGHTED:
+         for(int i=0; i<rates_total; i++)
+            m_price[i] = (high[i]+low[i]+close[i]+close[i])/4.0;
+         break;
+      default:
+         return false;
+     }
+   return true;
+  }
+
+//+------------------------------------------------------------------+
+//|                                                                  |
+//+------------------------------------------------------------------+
+bool CVIDYAStdevCalculator_HA::PreparePriceSeries(int rates_total, ENUM_APPLIED_PRICE price_type, const double &open[], const double &high[], const double &low[], const double &close[])
+  {
+   double ha_open[], ha_high[], ha_low[], ha_close[];
+   ArrayResize(ha_open, rates_total);
+   ArrayResize(ha_high, rates_total);
+   ArrayResize(ha_low, rates_total);
+   ArrayResize(ha_close, rates_total);
+   m_ha_calculator.Calculate(rates_total, open, high, low, close, ha_open, ha_high, ha_low, ha_close);
+
+   if(ArraySize(m_price) != rates_total)
+      if(ArrayResize(m_price, rates_total) != rates_total)
+         return false;
+
+   switch(price_type)
+     {
+      case PRICE_CLOSE:
+         ArrayCopy(m_price, ha_close, 0, 0, rates_total);
+         break;
+      case PRICE_OPEN:
+         ArrayCopy(m_price, ha_open, 0, 0, rates_total);
+         break;
+      case PRICE_HIGH:
+         ArrayCopy(m_price, ha_high, 0, 0, rates_total);
+         break;
+      case PRICE_LOW:
+         ArrayCopy(m_price, ha_low, 0, 0, rates_total);
+         break;
+      case PRICE_MEDIAN:
+         for(int i=0; i<rates_total; i++)
+            m_price[i] = (ha_high[i]+ha_low[i])/2.0;
+         break;
+      case PRICE_TYPICAL:
+         for(int i=0; i<rates_total; i++)
+            m_price[i] = (ha_high[i]+ha_low[i]+ha_close[i])/3.0;
+         break;
+      case PRICE_WEIGHTED:
+         for(int i=0; i<rates_total; i++)
+            m_price[i] = (ha_high[i]+ha_low[i]+ha_close[i]+ha_close[i])/4.0;
+         break;
+      default:
+         return false;
+     }
+   return true;
+  }
+//+------------------------------------------------------------------+
+//+------------------------------------------------------------------+