script.js

const canvas = document.getElementById("lienzo")
console.log(canvas);
const ctx = canvas.getContext('2d');

canvas.width = window.screen.width;
canvas.height = window.screen.height;
console.log("height: " + screen.height);
const w = canvas.width;
const h = canvas.height;

ctx.fillStyle = '#000';
ctx.fillRect(0,0,w,h);

const cols = Math.floor(w/20) + 1;
const posicion_y = Array(cols).fill(0);

function matrix(){
    ctx.fillStyle = '#0001';
    ctx.fillRect(0,0,w,h);

    ctx.fillStyle = '#0f0';
    ctx.font = '15pt monospace';

    posicion_y.forEach((y,ind) => {
        const text = String.fromCharCode(Math.random() * 128);
        const x = ind * 20;
        ctx.fillText(text,x,y);
        if(y > 100 + Math.random() * 10000){
            posicion_y[ind] =0;
        }else posicion_y[ind] = y + 20;
    })
}

setInterval(matrix,50);