p5js_sierpinski.js

function setup() {
    createCanvas(6400, 4800)
    background(0)
    colorMode(HSB, 360, 100, 100)
    frameRate(1200);

}

function draw() {
    let x = 0
    let y = 0 
    for (let i = 0; i < 1000000; i++) {
      p = random([0,1,2])
      if (p == 0){
          x /= 2
          y = (y + 4800)/2
      }
      else if (p == 1){
          x = (x + 3200)/2
          y /= 2
      }
      else{
          x = (x + 6400)/2
          y = (y + 4800)/2
      }
      stroke(i%360, 100, 100)
      point(x, y)
    }
   noLoop()
}

copy it into the p5.js online editor and run it.