let x;

let y;

let dir;

​

let ANTUP = 0;

let ANTRIGHT = 1;

let ANTDOWN = 2;

let ANTLEFT = 3;

​

function setup() {

  createCanvas(400, 400);

  grid = make2DArray(width, height);

  x = width / 2;

  y = height / 2;

  dir = ANTUP;

}

​

function turnRight() {

  dir++;

  if (dir > ANTLEFT) {

    dir = ANTUP;

  }

}

​

function turnLeft() {

  dir--;

  if (dir < ANTUP) {

    dir = ANTLEFT;

  }

}

​

function moveForward() {

  if (dir == ANTUP) {

    y--;

  } else if (dir == ANTRIGHT) {

    x++;

  } else if (dir == ANTDOWN) {

    y++;

  } else if (dir == ANTLEFT) {

    x--;

  }

​

  if (x > width - 1) {

    x = 0;

  } else if (x < 0) {

    x = width - 1;

  }

  if (y > height - 1) {

    y = 0;

  } else if (y < 0) {

    y = height - 1;

  }

}

​

​

function draw() {

  strokeWeight(1);

  for (let n = 0; n < 100; n++) {

    let state = grid[x][y];

    if (state == 0) {

      turnRight();

      grid[x][y] = 1;

    } else if (state == 1) {

      turnLeft();

      grid[x][y] = 0;

    }

​

    stroke(color(255));

    if (grid[x][y] == 1) {

      stroke(color(0));

    }

    point(x, y);

    moveForward();

  }

}

​

function make2DArray(cols, rows) {

  let arr = new Array(cols);

  for (let i = 0; i < arr.length; i++) {

    arr[i] = new Array(rows);

    for (let j = 0; j < arr[i].length; j++) {

      arr[i][j] = 0;

    }

  }

  return arr;

}