// An algorithm for picking a random number based on monte carlo method
function acceptreject(formula) {
  // We do this “forever” until we find a qualifying random value.
  while (true) {
    // Pick a random value.
    let r1 = random(1);
    // Assign a probability.
    let probability = formula(r1);
    // Pick a second random value.
    let r2 = random(1);

    //{!3} Does it qualify?  If so, we’re done!
    if (r2 < probability) {
      return r1;
    }
  }
}

class Walker {
    constructor(x = 0, y = 0) {
        this.t = 0
        this.x = x
        this.y = y
    }

    step() {
        let dx, dy
        if (noise(this.t+20000) < 0.5) {
            let step = -1.5
            dx = random(-step, step)
            dy = random(-step, step)
        } else {
            let step = 0.5;
            dx = map(noise(this.t), 0, 1, -1, 1)*step;
            dy = map(noise(this.t+10000), 0, 1, -1, 1)*step;
        }

        this.x = (this.x + dx) % width
        this.y = (this.y + dy) % height
        this.t += 0.01
    }

    draw() {
        stroke(0)
        point(this.x, this.y)
    }
}

let walker

function setup() {
    createCanvas(640, 240)
    background(255)
    walker = new Walker(320, 120)
}

function draw() {
    walker.step();
    walker.draw();
}