let y = 0

let spacing = 10

​

function setup() {

    createCanvas(700, 700);

    background(0)

}

​

function draw() {

    stroke(255)

    if (random(1) > 0.5) {

        line(x, y, x + spacing, y + spacing)

    } else {

        line(x, y + spacing, x + spacing, y)

    }

    x += spacing

​

    if (x > width) {

        x = 0

        y += spacing

    }

​

    if (y > height) {

        noLoop()

    }

}