<!DOCTYPE html>
<html>
<!-- ahhh -->

<body style="margin:0;overflow: hidden;">
  <canvas id="myCanvas" width="10" height="10" style="display: block;box-sizing: border-box;">
    Your browser does not support the HTML5 canvas tag.</canvas>
  <script>
    let c = document.getElementById("myCanvas");
    let ctx = c.getContext("2d");
    ctx.canvas.width = window.innerWidth;
    ctx.canvas.height = window.innerHeight;

    let deg_per_sec = 30;
    let time = 120;
    let fps = 60;

    centerX = ctx.canvas.width / 2;
    centerY = ctx.canvas.height / 2;

    rotation = 0; //was = j = angle
    currentFrame = 0; //was = i


    function render() {
      if (currentFrame < time / (1 / fps)) {
        setTimeout(() => {
          render();
          render_clear();

          draw_triangle(0, 200, "red");

        }, 1000 / fps);
        rotation += deg_per_sec / fps; // was = j = angle, now = rotation
        currentFrame += 1; // was = i
      }
    }

    render();

    function draw_triangle(ang, radius, colour) {
      ctx.beginPath();
      ctx.moveTo(centerX + Math.cos(rad(90 + 120 * 1 + ang)) * radius, centerY + Math.sin(rad(90 + 120 * 1 + ang)) * radius);
      ctx.lineTo(centerX + Math.cos(rad(90 + 120 * 2 + ang)) * radius, centerY + Math.sin(rad(90 + 120 * 2 + ang)) * radius);
      ctx.lineTo(centerX + Math.cos(rad(90 + 120 * 3 + ang)) * radius, centerY + Math.sin(rad(90 + 120 * 3 + ang)) * radius);
      ctx.lineTo(centerX + Math.cos(rad(90 + 120 * 1 + ang)) * radius, centerY + Math.sin(rad(90 + 120 * 1 + ang)) * radius);
      ctx.strokeStyle = colour;
      ctx.stroke();
    }

    function rad(degrees) {
      var pi = Math.PI;
      return degrees * (pi / 180);
    }


    function render_clear() {
      ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height);
      ctx.fillStyle = "black";
      ctx.fillRect(0, 0, ctx.canvas.width, ctx.canvas.height);
    }

  </script>
</body>

</html>