// Initialize Bar Graph Variables:
int Tank = 10; // Initial value of Tank
int c = 0;    // Initial value of c

void setup() 
{
  for(int i = 0; i < 12; i++)
  {
    pinMode(i, OUTPUT); // Set pins 0 to 11 as OUTPUT
  } 
}

void loop() 
{ 
  // Turn on the first 'Tank' number of LEDs
  for(int i = c; i < Tank; i++)
  {
    digitalWrite(i, HIGH); // Turn on LED at pin i
    delay(50); // Short delay between turning on each LED
    c++;
  }
  
  delay(1000); // Wait for a second before changing Tank
  
  Tank = 6; // Update the value of Tank
   
  // If c is greater than Tank, turn off the LEDs from c down to Tank
  if (c > Tank)
  {
    for (int i = c - 1; i >= Tank; i--)
    {
      digitalWrite(i, LOW); // Turn off LED at pin i
      delay(50); // Short delay between turning off each LED
    }
  }
  
  delay(1000); // Wait for a second before the next iteration
}