为什么会出现白框？

Question

循环输出的第一个框是一个带有黑色轮廓的白色框。我不明白它来自哪里...... https://editor.p5js.org/matranson/present/6fNelJM8_function setup() {    colorMode(HSB,360,100,100);    createCanvas(400, 400);    var boxh = height / 10;    var boxw = width;    for(var i = 0; i < 10; i++) {    var h = lerp(64, 22, i / 9);    var s = lerp(86, 90, i / 9);    var l = lerp(96, 56, i / 9);    rect(0, i * boxh, boxw, boxh);    fill(h,s,l);       stroke(0,0,100);    }    }function draw() {}<script src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/0.8.0/p5.js"></script>