Draw chess pattern grid

grid.pde

void drawGrid() {
  push();
  stroke(0);
  boolean switch_color = false;
  for (int line = 0; line <= width; line += cell_size) {
    for (int column = 0; column <= height; column += cell_size) {
      if (switch_color) {
        fill(255);
        switch_color = false;
      }  else {
        fill(0);
        switch_color = true;
      }
      rect(line, column, cell_size, cell_size);
      // rect(line, cell_size, width - cell_size, spacing);
      // line += spacing;
      // fill(255, 0, 0);
    }
  }
  pop();
}