let drawLine = (x0, y0, x1, y1, color) => {
  // Calculate "deltas" of the line (difference between two ending points)
  let dx = x1 - x0;
  let dy = y1 - y0;
  console.log("dy = "+dy);
  // Calculate the line equation based on deltas
  let D = (2 * dy) - dx;
  let y = y0;
  // Draw the line based on arguments provided
  for (let x = x0; x < x1; x++)
  {
      // Place pixel on the raster display
      putPixel(x,y,color);
      if (D >= 0)
      {
           y = y + 1;
           D = D - 2 * dx;
      }
      D = D + 2 * dy;
  }
};