// Example of using a while loop

void setup ()
{
  size(400, 400);
  background(200);
}

void draw ()
{
  background(50);
  int xCoord = mouseX;
  int yCoord = mouseY;
  int numColumns = 8;
  boolean squareIsBlack = true;
  
  int numRows = 8;
  
  while (numRows > 0)
  {
    numColumns = 8;
    xCoord = mouseX;
    while (numColumns > 0)
    {
      if (squareIsBlack == true)
      {
        fill(0); // Draw a black rectangle
      }
      else
      {
        fill(255, 0, 0); // Draw a red square
      }
      
      rect(xCoord, yCoord, 25, 25);
      xCoord = xCoord + 25;
      numColumns = numColumns - 1;
      squareIsBlack = !squareIsBlack;
    } // ends inner while loop (row)
    
    squareIsBlack = !squareIsBlack;
    numRows = numRows - 1;
    yCoord = yCoord + 25; // Drop down
  }
}