var rows = 1;

var colW, rowH;

var invert = false;

​

function setup() {

  createCanvas(windowWidth, windowHeight);

  init();

  noStroke();

}

​

function draw() {

  background(0);

​

  // Draw the cells

  for (var col = 0; col < cols; col++) {

    for (var row = 0; row < rows; row++) {

      if ((col % 2 == 0 && row % 2 == 1) || (col % 2 == 1 && row % 2 == 0)) fill(invert ? 255 : 0);

      else fill(invert ? 0 : 255);

​

      // Calculate x,y location of each cell

      var x = col * colW;

      var y = row * rowH;

      rect(x, y, colW, rowH);

    }

  }

}

​

// Set column width and row height based on num of cols and rows.

function init() {

  colW = width / cols;

  rowH = height / rows;

}

​

function keyPressed() {

  // Adjust number of columns and rows

  // ESC inverts black and white

  switch (keyCode) {

    case ESCAPE:

      invert = !invert;

      break;

    case RIGHT_ARROW:

      cols++;

      break;

    case LEFT_ARROW:

      cols--;

      break;

    case UP_ARROW:

      rows++;

      break;

    case DOWN_ARROW:

      rows--;

      break;

  }

​

  // Limit cols/rows to 0-10

  cols = constrain(cols, 0, 10);

  rows = constrain(rows, 0, 10);

​

  // Re-initialize colW and rowH

  init();

​

}