createCanvas(windowWidth, windowHeight);

  colorMode(HSB, 360, 100, 100);

  noStroke();

}

​

function draw() {

  background(220);

  // Draw 10 swatches

  for (let col = 0; col < 10; col++) {

    // Calculate brightness linearly

    // Each swatch is 10% brighter

    let b = col*10;

    // Calculate x-position of swatch

    let x = col * width / 10;

    // Draw the swatch

    fill(0, 0, b);

    rect(x, 0, width / 10, height/2);

  }

  // Draw 10 swatches

  for (let col = 0; col < 10; col++) {

    // Calculate brightness exponentially

    // where is this from??

    let b = pow(2, (col/2+2));

    // below, actual exponential interpolation

    // doesn't look good

    // let b = pow(91, (col/9)) - 1;

    // Calculate x-position of swatch

    let x = col * width / 10;

    // Draw the swatch

    fill(0, 0, b);

    rect(x, height/2, width / 10, height);

  }

}

​

​