optical illusion

illusion.js

background(0,0,0);
var radius = 1;

var drawCircle = function(rad) {
    translate(200, 200);
    for(var r = 0; r < 360; r += 2) {
        fill(20, mouseY, mouseX);
        rect(rad, rad, 20, 20);
        rotate(2);
    }
};

var draw = function() {
    pushMatrix();
    drawCircle(radius);
    popMatrix();
    radius = (radius + 2) % 160;
};