html, body {
	background: #000;
}

canvas {
	margin-left: calc(50% - 300px);
	margin-top: 100px;
}
let x = 0;
let y = 0;
let spacing = 10;

//Set up basic canvas
function setup() {
	createCanvas(600, 400);
	background(0);
}

function draw() {	
	//If y is within the height of the canvas
	if(y < height) {
		
		//Pirck a random gray color
		stroke(random(100, 255));
		
		//Generate a random number upto 1. If it's less than .5
		if(random(1) < .5) {
			//backslash line \
			line(x, y, x + spacing, y + spacing);
		} else { //More than .5
			//forwardslash line /
			line(x, y + spacing, x + spacing, y);
		}

		// Move along one space
		x = x + spacing;

		//If we're at the end of the canvas, go down one line
		if(x > width) {
			x = 0;
			y = y + spacing;
		}
	}
}

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

  1. https://cdnjs.cloudflare.com/ajax/libs/p5.js/0.6.0/p5.js