Land grading

const DEAD = 0;

const ALIVE = 1;

const n = 300;

const brushThickness = 5;

let cells;

let g;

​

function setup() {

  p5.disableFriendlyErrors = true;

  const m = min(windowWidth, windowHeight);

  createCanvas(m, m);

​

  cells = new Uint8Array(n * n).fill(DEAD);

​

  g = createGraphics(n, n);

  g.background(0).pixelDensity(1).loadPixels();

}

​

function draw() {

  background("white");

  brush();

​

  let next = new Uint8Array(cells);

  for (let y = 1; y < n - 1; y++) {

    for (let x = 1; x < n - 1; x++) {

      const i = x + y * n;

      const sum0 = 

        cells[i + 1] 

      + cells[i - 1] 

      + cells[i - n] 

      + cells[i + n];

      const sum1 =

      + cells[i - 1 - n] 

      + cells[i - 1 + n] 

      + cells[i + 1 - n] 

      + cells[i + 1 + n];

      const all = sum0 + sum1;

​

      const status = cells[i] 

      ? all < 1 || all > 4 

      : sum0 > sum1 * 2;

      next[i] = status;

      g.pixels[i * 4 + 3] = status ? 0 : 255;

    }

  }

  cells = next;

  g.updatePixels();

  image(g, 0, 0, width, height);

}

​

function brush() {

  let mx = ceil(map(mouseX, 0, width, 0, n - 1));

  let my = ceil(map(mouseY, 0, height, 0, n - 1));

​

  const b = brushThickness;

  for (dy = -b; dy <= b; dy++) {

    for (dx = -b; dx <= b; dx++) {

      let d = sqrt(dx ** 2 + dy ** 2);

      if (d > b) continue;

      let x = mx + dx;

      let y = my + dy;

      if (x < 0 || x >= n || y < 0 || y >= n) continue;

      cells[x + y * n] = mouseIsPressed

        ? random(2) < 1 ? ALIVE : DEAD

        : ALIVE;

    }

  }

}