A CodePen by mareis. Spiralillusjon

index.html

<canvas id="canvas"></canvas>

script.js

var canvas = document.getElementById("canvas");
var ctx = canvas.getContext('2d');

canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
var b = canvas.width;
var h = canvas.height;
var teller = 0;
var offset = 0;
var xPos, fontS, farge1, farge2;

function spiral(){
    ctx.fillStyle = "#000";
    ctx.fillRect(0,0,b,h);
    for(var yPos = 0; yPos<=h; yPos+=15){
        xPos = (b/6) * Math.sin(teller + offset) + (b/2);
        fontS = 50 * Math.cos(teller + offset)+60;
        farge1 = Math.floor(125*(Math.sin(teller+offset+Math.PI)+1));
        farge2 = Math.floor(125*(Math.cos(teller+offset+Math.PI)+1));
        ctx.fillStyle = "rgba("+farge2+","+farge1+","+farge1+",0.7)"
        ctx.fillText("0", xPos, yPos);
        ctx.font = fontS + "px Arial";
        offset = offset + 0.2;
    }
    offset = 0;
    teller=teller + 0.05;
}
setInterval(spiral,20);

style.css

body{
  margin:0;
}